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Eine konsequente Berucksichtigung individueller Faktoren in der praktischen Arzneimitteltherapie konnte helfen, diese sicherer und effizienter zu gestalten. In der Onkologie findet eine individuell zugeschnittene Arzneimitteltherapie durch Behandlungen, die eine Bestimmung molekularer Tumormarker voraussetzen, zunehmende Verbreitung. Die pharmakogenetische Diagnostik im engeren Sinne, also die molekulargenetische oder pharmakologische Messung individueller Besonderheiten bei der Medikamentenwirkung oder im Medikamentenstoffwechsel, wird aber bislang in der medizinischen Praxis wenig angewendet. Fehlende Daten, ein fehlendes Wissen um die Zusammenhange, die begrenzte Verfugbarkeit entsprechender Labordiagnostik ebenso wie die Tatsache, dass nur ein kleiner Teil der Patienten von dieser neuen Diagnostik profitieren kann, gehoren zu den Ursachen fur die geringe Verbreitung der pharmakogenetischen Diagnostik. Dabei gibt es insbesondere im Bereich der Pharmakokinetik (also Absorption, Metabolismus und Elimination von Medikamenten) klare Konzepte fur eine pharmakogenetisch optimierte Therapie. Diese Konzepte basieren auf dem Bioaquivalenzprinzip und sind auch Grundlage der individuellen Arzneitherapie in anderen Bereichen wie die Berucksichtigung von Leber- und Nierenerkrankungen und von Arzneimittelwechselwirkungen. Zunehmend wird auf die mogliche Bedeutung pharmakogenetischer Varianten in den Arzneimittelinformationen fur Arzte hingewiesen. Die von der FDA herausgegebenen Arzneimittelinformationen nennen pharmakogenetische Faktoren immerhin bei inzwischen mehr als 60 Medikamenten, meist jedoch, ohne konkrete Handlungsanweisungen fur die Arzte zu geben. Diese Lucke versuchen wir im Bereich der Pharmakokinetik zu schliesen, aber auch internationale Konsortien, wie z. B. das Clinical Pharmacogenetics Implementation Consortium of the Pharmacogenomics Research Network (CPIC), haben sich zum Ziel gesetzt, Leitlinien fur eine Dosis- oder Therapieanpassung basierend auf pharmakogenetischer Diagnostik herauszugeben, und dies auf Grundlage der jeweils besten verfugbaren Evidenz.

Heritability of caffeine pharmacokinetics and cytochrome P450 1A2 (CYP1A2) activity is controversial. Here, we analyzed the pharmacokinetics of caffeine, an in vivo probe drug for CYP1A2 and arylamine N-acetyltransferase 2 (NAT2) activity, in monozygotic (MZ) and dizygotic (DZ) twins. In the entire group, common and unique environmental effects explained most variation in caffeine area under the curve (AUC). Apparently, smoking and hormonal contraceptives masked the genetic effects on CYP1A2 activity. However, when excluding smokers and users of hormonal contraceptives, 89% of caffeine AUC variation was due to genetic effects and, even in the entire group, 8% of caffeine AUC variation could be explained by a CYP1A1/1A2 promotor polymorphism (rs2470893). In contrast, nearly all of the variations (99%) of NAT2 activity were explained by genetic effects. This study illustrates two very different situations in pharmacogenetics from an almost exclusively genetic determination of NAT2 activity with no environmental modulation to only moderate genetic effects on CYP1A2 activity with strong environmental modulation.

Pharmacogenetics are an important component in the individualization of treatment; however, pharmacogenetic diagnostics have so far not been used to any great extent in clinical practice. A consistent consideration of individual patient factors, such as pharmacogenetics may help to improve drug therapy and increase individual safety and efficacy aspects.A brief summary of structures and effects of genetic variations on drug efficacy is presented. Some frequently prescribed pharmaceuticals are specified. Furthermore, the feasibility of pharmacogenetic diagnostics and dose recommendations in the clinical practice are described.The European Medicines Agency (EMA) as the European approval authority has already extended the drug labels of more than 70 pharmaceuticals by information on pharmacogenetic biomarkers and the U.S. Food and Drug Administration (FDA) more than 150. This is a crucial step towards targeted medicine. Guidelines on dose and therapy adjustments are provided by the Clinical Pharmacogenetics Implementation Consortium of the Pharmacogenomics Research Network.It is fundamental to consider individual patient factors for successful drug therapy. Dose and therapy recommendations based on pharmacogenetic diagnostics are highly important for individualization as well as improvement of safety and efficiency of drug therapy.

The growing interest in incorporating pharmacogenetics (PGx) into drug development and clinical practice raises several questions: which study designs best reveal relevant pharmacogenetic biomarkers, best clarify specific hypotheses in PGx, and result in the largest gain of clinical evidence in this field? In this review, we present and compare a variety of PGx-related study designs. The type and quality of evidence gained by each category of study design is evaluated, and an appropriate timeline for the integration of pharmacogenetic studies into drug development is proposed. A summary of the pros and cons of the different study designs might help investigators decide how best to incorporate PGx into drug research. Using different scenarios to explain how genetic polymorphisms influence drug action, we illustrate how this knowledge can be translated into individualized drug choices, individualized dosage determination based on pharmacogenetic diagnostics, and other types of monitoring in order to make drug therapies safer and more effective.

Little is known about the genetic impact on loop diuretic effects. We newly investigated five genetic polymorphisms in 95 healthy volunteers, who had ingested bumetanide, frusemide and torsemide. The subjects excreted means of 20.2 g sodium chloride, 2.87 g potassium and 261 mg calcium over 24 h. Concerning sodium chloride, the subjects excreted 2.2 g less per two T-alleles of C825T in the G nucleotide β-subunit 3 (GNB3), 3.2 g less per two Met32-alleles of Val32Met in the atrial natriuretic peptide precursor (ANP) and 2.8 g more per two Arg152-alleles of Ter152Arg in ANP (P=0.007, 0.05 and 0.007). Concerning potassium, the subjects excreted 0.42 g more per two ANP Arg152-alleles (P=0.023). Concerning calcium, the subjects excreted 32 mg more per two deletion-alleles of the insertion/deletion polymorphism in the angiotensin-converting enzyme, 44 mg more per two Trp460-alleles of Gly460Trp in α-adducin (ADD1) and 42 mg less per two GNB3 T-alleles (P=0.006, 0.023 and 0.008). The common genetic impact together with three polymorphisms in the sodium chloride cotransporter and the epithelial sodium channel was 20, 15, 10 and 23% of the variation in the urinary excretion of sodium chloride, volume, potassium and calcium. This exceeded the fraction of variation explained by differences in the pharmacokinetics: 13, 10, 11 and 6%. Thus, genetic variation seems to be a stronger predictor of the loop diuretic drug response than pharmacokinetic variation.

Pharmacokinetics in individual subjects is determined by genes and environment. The relative contributions of enzyme induction and inherited genomic variation to cytochrome P450 enzyme 2C9 (CYP2C9) activity are unknown. In 130 volunteers, CYP2C9 activity was measured in vivo using tolbutamide as a probe drug. Tolbutamide was administered orally, and the pharmacokinetics of the drug was analyzed twice—before and after four doses of 450 mg rifampin. Mean total apparent clearances (Cl/F) in the genotype groups CYP2C9*1/*1, *1/*2, *1/*3, *2/*3, and *3/*3 before rifampin were 0.78, 0.74, 0.52, 0.40, and 0.13 l/h, respectively. After rifampin administration, these clearances increased in all genotype groups by a median factor of 1.9 (range 1.1–4.8). The combined effects of genes and environment could be predicted by a simple additive model. Thus, enzyme induction resulted in an approximately twofold difference in CYP2C9 activity, irrespective of the CYP2C9 genotypes. But the difference in activity levels between the CYP2C9*1/*1 and *3/*3 genotypes before the administration of rifampin was sixfold. Clinical Pharmacology & Therapeutics (2009); 86, 1, 54–61 doi:10.1038/clpt.2009.40

The impact of the CYP2C9 polymorphism on the pharmacokinetics of orally administered 9-tetrahydrocannabinol (THC) was studied in 43 healthy volunteers. THC pharmacokinetics did not differ by CYP2C9*2 allele status. However, the median area under the curve of THC was threefold higher and that of 11-nor-9-carboxy-9-tetrahydrocannabinol was 70% lower in CYP2C9*3/*3 homozygotes than in CYP2C9*1/*1 homozygotes. CYP2C9*3 carriers also showed a trend toward increased sedation following administration of THC. Therefore, the CYP2C9*3 variant may influence both the therapeutic and adverse effects of THC.

The concentration ratio of morphine (Mor) over codeine (Cod) in opiate positive blood samples is used to discriminate between the use of illegal heroin (high ratios) and therapeutic codeine (low ratios). However, genetically caused CYP2D6 ultra-rapid metabolism might lead to Mor/Cod comparable to heroin intake. A single oral dose of 30 mg codeine was administered to 11 CYP2D6 ultrarapid metabolizers (UMs) and 12 extensive metabolizers (EMs). Codeine and its morphine metabolites and Mor/Cod were quantified in plasma and urine by liquid chromatography with tandem mass spectrometry within 24 h after codeine intake. The Mor/Cod in plasma were below 1 for both UMs and EMs during the first 12 h. After 12 h, 9% of the 11 UM and none of the 12 EM had ratios > 1. In urine, Mor/Cod ratios were below one for all EMs and UMs during the first 12 h. Thus, CYP2D6 genotyping in general will not explain Mor/Cod ratios > 1 in plasma or urine, unless the time of drug intake is more than 24 h previous.

Genetic polymorphisms in superoxide-producing NAD(P)H oxidase have been linked to cardiovascular diseases including anthracycline-induced cardiotoxicity. We quantified NAD(P)H oxidase activity in granulocytes of 81 healthy Caucasian volunteers (in addition, 51 in an independent confirmatory study) by chemiluminescence using the luminol analogue L-012. Expression of CYBA, NCF4 and RAC2 coding for NAD(P)H oxidase subunits was measured in whole blood cells in 59 study participants by real-time PCR. Of the five variants investigated (−930A>G, 242C>T, 640A>G in CYBA and the recently reported −368G>A in NCF4 and 7508T>A in RAC2), only CYBA 640A>G was consistently associated with superoxide production (640GG carriers 28% less than AA individuals, P=0.05 in each cohort, P=0.005 in combined analysis). RAC2 7508T>A was related to higher expression of RAC2 (P=0.02) and NCF4 (P=0.04). In summary, CYBA 640A>G rather than 242C>T was associated with reduced activity. The quantitatively moderate effect and the high intra-individual variability should be considered for further study design.

There is little data on genetic predictors of loop diuretic efficacy in humans. Therefore, we investigated the diuretic effects of single oral doses of bumetanide, frusemide, and torsemide in a crossover study in 97 healthy Caucasians in relation to genetic variation in the renal sodium transporters NKCC2 (coded by SLC12A1), NCC (SLC12A3), and ENaC (three subunits coded by SCNN1A, SCNN1B, and SCNN1G). The NCC alanine 264 allele (Gly264Ala) and the most frequent SCNN1B haplotype were associated with stronger diuresis, indicating lower reabsorbing function of these alleles. The variant alleles of the tightly coupled polymorphisms rs5723 (Leu649Leu) and rs5729 in SCNN1G were associated with weaker diuresis, indicating higher activity. Extended haplotype homozygosity implied evolutionary selection of the NCC alanine 264 allele. In conclusion, acute diuretic effects of loop diuretics were affected by genetic variation in sodium transporters that, in the nephron, are located distally from NKCC2.

The low bioavailability of the anti-migraine drug sumatriptan is partially caused by first-pass hepatic metabolism. In this study, we analyzed the impact of the hepatic organic cation transporter OCT1 on sumatriptan cellular uptake, and of OCT1 polymorphisms on sumatriptan pharmacokinetics. OCT1 transported sumatriptan with high capacity and sumatriptan uptake into human hepatocytes was strongly inhibited by the OCT1 inhibitor MPP(+) . Sumatriptan uptake was not affected by the Met420del polymorphism, but was strongly reduced by Arg61Cys and Gly401Ser, and completely abolished by Gly465Arg and Cys88Arg. Plasma concentrations in humans with two deficient OCT1 alleles were 215% of those with fully active OCT1 (P = 0.0003). OCT1 also transported naratriptan, rizatriptan, and zolmitriptan, suggesting a possible impact of OCT1 polymorphisms on the pharmacokinetics of other triptans as well. In conclusion, OCT1 is a high-capacity transporter of sumatriptan and polymorphisms causing OCT1 deficiency have similar effects on sumatriptan pharmacokinetics as those observed in subjects with liver impairment.

The hopes for readily implementable precision medicine are high. For many complex disorders, such as bipolar disorder, these hopes critically hinge on tangible successes in pharmacogenetics of treatment response or susceptibility to adverse events. In this article, we review the current state of pharmacogenomics of bipolar disorder including latest results from candidate genes and genome-wide association studies. The majority of studies focus on response to lithium treatment. Although a host of genes has been studied, hardly any replicated findings have emerged so far. Very small samples sizes and heterogeneous phenotype definition may be considered the major impediments to success in this field. Drawing from current experiences and successes in studies on diagnostic psychiatric phenotypes, we suggest several approaches for our way forward.

In 97 unselected volunteers and two additional homozygous carriers of CYP2C9(*)3, we investigated the oral clearance of torsemide in relation to 37 polymorphisms at the CYP2C gene locus. Torsemide total oral clearance was linearly associated with the number of CYP2C9(*)3 alleles (geometric mean: 59, 40 and 20 ml/min in carriers of no, one and two alleles) and so were the methyl- and ring-hydroxylation but not the carboxylation clearance. Haplotypes including the CYP2C9(*)3 allele were similarly associated with the clearances but no other variant and no haplotype not including the CYP2C9(*)3 variant. The extended haplotype length (EHL) of the CYP2C9 haplotypes was positively associated with higher activity of the gene product. Torsemide total oral clearance was predictable with r(2)=82.1% using plasma concentrations at 0.5, 1, 2 and 24 h. In conclusion, torsemide's biotransformation strongly depended on the CYP2C9(*)3 variant but no other. Higher clearance CYP2C9 haplotypes appear to be evolutionarily selected.

Genetische Faktoren beeinflussen zu einem hohen Mase die Pharmakokinetik und Wirkung von Antidepressiva. Die modernen Methoden der Genotypisierung ermoglichen eine schnelle und kostengunstige Bestimmung genetischer Varianten und konnen deshalb als klinische Diagnostik zur Verbesserung der individuellen Vertraglichkeit der Arzneitherapie eingesetzt werden. Die Bedeutung genetischer Varianten in Enzymen des Arzneimittelstoffwechsels, Arzneistofftransportern, Neurotransmitterrezeptoren und -transportern sowie in Molekulen der Signaltransduktion wurden in zahlreichen Studien an gesunden Probanden und an Patienten untersucht. Wahrend genetische Varianten in den arzneistoffmetabolisierenden Zytochrom-P450-Enzymen der Leber fur grose interindividuelle Unterschiede in der oralen Clearance, Halbwertszeit und Bioverfugbarkeit verantwortlich sind, sind die Auswirkungen genetischer Varianten im Bereich der Antidepressiva-Zielstrukturen weniger eindeutig charakterisiert. Da genetische Zusammenhange nur dann in der Praxis von Bedeutung sind, wenn sie zu konkreten Folgen fur die Therapie fuhren, soll in diesem Artikel ein Uberblick uber die derzeitig vorhandene Literatur gegeben werden. Aufgezeigt werden soll, in welchen Fallen die Bestimmung pharmakogenetischer Varianten zu einer individuelleren Arzneimitteltherapie durch genotypbasierte Anpassung der Arzneimitteldosierung fuhren konnte.

Aims The genetically polymorphic cytochrome P450 (CYP) enzyme CYP2C9 metabolizes most sulphonylurea oral hypoglycaemic agents. The aim of this study was to test the hypothesis that individuals with genotypes predicting low CYP2C9 activity may be at a higher risk of severe drug-associated hypoglycaemia. Methods In a case-control study, 20 diabetic patients admitted to the emergency department with severe hypoglycaemia during sulphonylurea drug treatment were compared with a control group of 337 patients with type 2 diabetes but without a history of severe hypoglycaemia. A large sample of 1988 healthy Caucasian subjects served as a second control group. Results The CYP2C9 genotypes *3/*3 and *2/*3 that are predictive of low enzyme activity were more common in the hypoglycaemic group than in the comparison groups (10%vs

Purpose: Since public acceptance of pharmacogenetic testing will largely influence their implementation in routine medical care, common implications of pharmacogenetic testing from patients', physicians' and scientists' perspective are reviewed. Methods: Broad literature review (MEDLINE; MeSH terms: Pharmacogenetics, Delivery of Health Care, Ethics, Attitude, Patient Acceptance of Health Care) of empirical and theoretical studies describing psychological, family-related, social, and ethical consequences of pharmacogenetic testing to describe relevant aspects for further empirical studies. Results: Apart from anticipated benefit, acceptance of pharmacogenetic testing might be influenced by the following: Expectation of negative psychosocial consequences, fear of discrimination or violation of privacy. Due to its great complexity, understanding of test results and explanation of their impact pose new challenges for physician-patient relations. Since most studies are conceptual, empirical studies exploring attitudes of patients/physicians and determining medical as well as economic value of pharmacogenetic testing are imperative.

The broad clinical application of pharmacogenetic diagnostics for individualised drug treatment is still limited. With the exception of oncological therapies where molecular tumor makers are frequently used to decide upon individual drug therapies, pharmacogenetic testing is not generally offered in clinical laboratory diagnostics, because the costs are not covered by general health insurance and it is not evident what consequences the results of a genotyping test may have for the individual drug treatment. Especially in the context of pharmacokinetics, bioequivalence-based concepts have been developed that allow the individual drug dosage or therapy to be adjusted to genetic polymorphisms in drug metabolism, drug transport that affect drug absorption, metabolism and elimination. Pharmacogenetic aspects are increasingly included in the product information (e.g., on its website the FDA lists more than 60 drug labels that include pharmacogenetic information). However, most pharmacogenetic information on drug labels does not give recommendations for clinical decisions to be made based on individual genotypes. This gap is currently being closed by the development of international consortia aiming to base clinical recommendations on the best available evidence by systematic review of the existing data. The Clinical Pharmacogenetics Implementation Consortium of the Pharmacogenomics Research Network (CPIC) is an international community-driven organisation that is developing peer-reviewed, freely available gene/drug guidelines that are published in full at PharmGKB (http://www.pharmgkb.org). The aim of these guidelines is to give therapeutic recommendations such as dose adjustments or suggestions for the choice of an alternative drug in the case of specific genotypes (phenotypes) that predict slow metabolism or transport of drugs or safety risks or risks of therapeutic failure. These guidelines are not mandatory but serve to facilitate the translation of pharmacogenetic knowledge from bench to bedside.

The single- and multiple-dose pharmacokinetics of the naphthodianthrones hypericin and pseudohypericin derived from St. John's wort (Hypericum perforatum, LI 160, Lichtwer Pharma GmbH, Berlin) were studied in 12 healthy male subjects. After a single oral dose of 300, 900, or 1800 mg of dried hypericum extract (250, 750, or 1500 μg hypericin and 526, 1578, or 3156 μg pseudohypericin), plasma levels were measured with a modified highly sensitive high-pressure liquid chromatography (HPLC) method (lower detection limit 0.1 ng/mL) up to 3 days. The median maximal plasma levels were 1.5, 4.1, and 14.2 ng/mL for hypericin and 2.7, 11.7, and 30.6 ng/mL for Pseudohypericin, respectively, for the three doses given above (interim evaluation of four volunteers). The median elimination half-life times of hypericin were 24.8 to 26.5 hours, and varied for pseudohypericin from 16.3 to 36.0 hours. Ranging between 2.0 to 2.6 hours, the median lag-time of absorption was remarkably prolonged for hypericin when compared to pseudohypericin (0.3 to 1.1 hours). The areas under the curves (AUC) showed a nonlinear increase with raising dose; this effect was statistically significant for hypericin. During long-term dosing (3 x 300 mg/day), a steady-state was reached after 4 days. Mean maximal plasma level during the steady-state treatment was 8.5 ng/mL for hypericin and 5.8 ng/mL for pseudohypericin, while mean trough levels were 5.3 ng/mL for hypericin and 3.7 ng/mL for pseudohypericin. In spite of their structural similarities there are substantial Pharmacokinetic differences between hypericin and pseudohypericin.

A patient suffering from a rare enzyme deficiency developed a malignant neuroleptic syndrome after having been treated with one single dose of haloperidol. We investigated the patient's serum for all frequent polymorphisms in cytochrome P450 2D6, assuming him to be a poor neuroleptic metabolizer. We will also discuss other potential mechanisms inducing this disturbance and its differential diagnoses.

We investigated whether tramadol or its active metabolite, O-desmethyltramadol, are substrates of the organic cation transporter OCT1 and whether polymorphisms in OCT1 affect tramadol and O-desmethyltramadol pharmacokinetics. Tramadol showed high permeability through parallel artificial membrane permeability assays (PAMPAs). Tramadol uptake in HEK293 cells did not change after OCT1 overexpression, and the concentrations of tramadol in the plasma of healthy volunteers were independent of their OCT1 genotypes. In contrast, O-desmethyltramadol showed low membrane permeability, and OCT1 overexpression increased O-desmethyltramadol uptake 2.4-fold. This increase in uptake was reversed by OCT1 inhibitors and absent when loss-of-function OCT1 variants were overexpressed. Volunteers carrying loss-of-function OCT1 polymorphisms had significantly higher plasma concentrations of O-desmethyltramadol (P = 0.002, n = 41) and significantly prolonged miosis, a surrogate marker of opioidergic effects (P = 0.005, n = 24). In conclusion, polymorphisms in OCT1 influence the pharmacokinetics of O-desmethyltramadol, presumably by affecting its uptake into liver cells, and thus may modulate the efficacy of tramadol treatment.

The paper deals with engineering aspects of the design of membrane systems for the separation and recovery of volatile hydrocarbons from off-gases. The membrane which is used for this application is a thin film composite membrane with an elastomeric selective top layer. This membrane has a high permeability for various hydrocarbon vapors and a low permeability for oxygen and nitrogen. The membrane configuration is a flat sheet membrane manufactured to an envelope with a round shape which is installed in the so-called GS module. The energy impact in accordance with the condensation mode and operating pressures is shown. Case studies on the influence of different process parameters, e.g., plant capacity, recovery rate, pressure ratio, stage cut and retentate concentration were carried out on the basis of given feed compressor and vacuum pump capacities. Finally, the investment costs of vapor recovery units in gasoline tank farms are discussed.

After uptake into liver cells, the antiemetic drugs tropisetron and ondansetron undergo metabolic inactivation by cytochrome P450 2D6 (CYP2D6). We investigated whether the hepatic organic cation transporter 1 (OCT1; SLC22A1) mediates cellular uptake and whether common OCT1 loss-of-function polymorphisms affect pharmacokinetics and efficacy of both drugs. Both tropisetron and ondansetron inhibited ASP+ uptake in OCT1-overexpressing HEK293 cells. Overexpression of wild-type, but not OCT1 loss-of-function variants, significantly increased tropisetron uptake. Correspondingly, patients with two loss-of-function OCT1 alleles had higher tropisetron plasma concentrations (n=59, P

Omeprazole has been shown to induce cytochrome P450IA1 and P450IA2 activity in vitro. To reflect cytochrome P450IA2 (CYP1A2) activity in vivo, the 13C-[N-3-methyl]-caffeine breath test was conducted in 18 volunteers: 12 extensive metabolizers, one intermediate metabolizer, and five poor metabolizers of S-mephenytoin. Breath tests were performed before treatment with an oral dose of 40 mg omeprazole, on the seventh day of treatment, and after a 7-day washout period. The mean percentage exhalation of the 13C test dose, as determined by 13CO2 in breath during 8 hours, was 23.0% +/- 8.0% (n = 18) before treatment. The largest increases in exhalation rate of 13CO2 were observed in the poor metabolizers and the intermediate metabolizers (range, 12.8% to 62.9%; median, 38.9%); median area under the plasma concentration-time curves (AUC) of omeprazole was four times higher than in the extensive metabolizers. The change after omeprazole treatment in extensive metabolizers ranged from -9.8% to +47.7% (median, 12.3%; n = 12) of pretreatment values. In both groups exhalation rates of 13CO2 returned to near pretreatment values within the 7-day washout period (24.2% +/- 7.8%; n = 17). Changes in the 13C-caffeine breath test correlated well with both the pretreatment value (R = -0.67, p = 0.003; n = 18) and the plasma AUC of omeprazole (R = 0.61, p = 0.007; n = 18). Therapeutic doses of omeprazole seem to induce CYP1A2 activity in poor metabolizers, whereas they exert minor inducing effects in extensive metabolizers of S-mephenytoin.

Glutathione S-transferase (GST) class Mu activity was determined in 145 unrelated hospital patients in Berlin by measuring their conjugation activity towards the specific substrate trans-stilbene oxide (TSO) with two substrate concentrations (50 and 250 microM) in homogenates prepared from lymphocytes. Eighty individuals (55.2%) had an activity lower than 10 pmol/min/10(6) lymphocytes and were classified as GST class Mu deficient. In 142 of 145 cases, phenotype was confirmed by the results of a genotyping procedure using the polymerase chain reaction technique. Two fragments of 273 and about 650 bp including one and two introns, respectively, could always be amplified from genomic DNA in individuals with high GST class Mu activity and could not be amplified in persons with impaired glutathione-TSO conjugation activity. This indicates that persons with low activity carry a large deletion mutation within the GST class Mu gene. The enzymatically determined antimode between low and high activity determined as 10 pmol/min/1 million lymphocytes in the assay with 50 microM TSO could be clearly confirmed by genotyping.

Pre-column labelling techniques are described for the determination of S-carboxymethyl-L-cysteine (CMC) and its metabolites in urine and plasma samples by high-performance liquid chromatography (HPLC) without prior extraction. All substances containing an amino group were converted into fluorescent fluorenylmethyl derivatives with 9-fluorenylmethyloxycarbonyl chloride (FMOC). Deaminated or N-acetylated carbocysteine metabolites were coupled with 1-pyrenyldiazomethane (PDAM) to give fluorescent PDAM esters. Similar results were obtained with the two commercially available and stable diazomethane derivatives PDAM and 9-anthryldiazomethane (ADAM). Following double derivatization with PDAM and FMOC, in a single chromatographic run with two fluorescence detectors connected in series, amines and amino(carboxylic) acids could be detected by their FMOC residues and, simultaneously, carboxylic acids were detected as fluorescent PDAM esters. The (R) and (S) enantiomers of the sulphoxides of CMC, of methylcysteine and of N-acetyl CMC were separated, although the reversed-phase HPLC system did not contain a chiral additive or stationary phase designed for the separation of enantiomers. The methods do not include liquid extraction steps and can therefore be performed either manually or automatically using an HPLC autosampler. These methods were used for the investigation of a disputed pharmacogenetic polymorphism of S-oxidation of CMC in humans, which until now has most often been studied using paper chromatography. The described techniques were applied to the determination of CMC and its metabolites in human urine and plasma samples.

Ganglioside GM1 multiple-dose pharmacokinetics were investigated in five healthy male volunteers. Doses of 100 mg were administered either intravenously or intramuscularly for 21 days, and the washout was followed-up for a further 21 days. The highly specific binding of the β-subunit of cholera toxin was used to quantify ganglioside GM1 levels in plasma, urine, and feces. This dose regime increased the ganglioside GM1 steady-state plasma levels two to three orders of magnitude above the endogenous levels of 0.132 mg/L (coefficient of variation, 8.9%). Large and variable amounts of ganglioside GM1 were found in feces before and during treatment without relation to the dosage. No ganglioside GM1 could be detected in urine at any time. Plasma kinetics were linear with a biexponential disposition. Exogenously administered ganglioside GM1 was confined mainly to the blood volume as indicated by a steady-state volume of distribution of 6.98 ± 3.57 L and appears to be excreted mainly in the form of metabolites. The total clearance was very slow at 1.61 ± 0.37 ml/min. Absorption after intramuscular administration was slow (time to reach maximum concentration >12 hours) and yielded steady-state concentrations somewhat lower compared with the intravenous infusion. Clinical Pharmacology and Therapeutics (1991) 50, 141–149; doi:10.1038/clpt.1991.118

A quantitative study has been made of the metabolism of S-carboxymethyl-L-cysteine (CMC) and its sulphoxides in volunteers by HPLC. Precolumn derivatization was applied prior to gradient reversed phase HPLC separation and fluorescence detection. For CMC and its metabolites containing a primary amino group the reagent 9-fluorenylmethylchloroformate was used. The other metabolites of CMC were derivatized at their carboxylic group with 1-pyrenyldiazomethane to give stable fluorescent products. Urine samples were collected for 8 h after oral administration of 1.125 g CMC to 33 healthy volunteers. Elimination of CMC in urine as sulphoxides did not account for more than 1% of the dose in any of the volunteers. Thus, CMC-sulphoxide metabolites are not quantitatively important. Recovery of the original substance in 8-hour urines ranged from 10 to 30% and a further 2 to 20% was recovered as the metabolite thiodiglycolic acid. Oral doses of 0.19, 1.125, and 2.25 g CMC in a second group of 12 healthy volunteers did not reveal dose dependence of the urinary excretion of the sulphoxides or of thiodiglycolic acid. Serum concentration-time-curves of CMC, (S)- and (R)-CMC sulphoxide were measured in a group of 9 healthy volunteers. The CMC sulphoxides in serum reached 1.5% of the parent substance after 4 hours. The ratio of CMC to its sulphoxide metabolites was similar in serum and urine. Pharmacogenetic polymorphism of sulphoxidation was not confirmed by the specific HPLC methods used.

Comparative potency of proton-pump inhibitors (PPIs) is an important clinical issue. Most available trials have compared the different PPIs at one or a few selected specific dosages, making it difficult to derive quantitative equivalence dosages. Here we derived PPI dose equivalents based on a comprehensive assessment of dose-dependent effects on intragastric pH. All available clinical studies reporting the effects of PPIs on mean 24-h intragastric pH were sought from electronic databases including Medline. Studies included were restricted to those targeting the Caucasian population, and healthy volunteers or gastroesophageal reflux disease (GERD) patients. The dose-effect relationships for mean 24-h intragastric pH and for percentage of time with pH > 4 in 24 h were analyzed for each PPI using pharmacodynamic modeling with NONMEM and a model integrating all available data. Fifty-seven studies fulfilled the inclusion criteria. Based on the mean 24-h gastric pH, the relative potencies of the five PPIs compared to omeprazole were 0.23, 0.90, 1.00, 1.60, and 1.82 for pantoprazole, lansoprazole, omeprazole, esomeprazole, and rabeprazole, respectively. Compared with healthy volunteers, patients with GERD needed a 1.9-fold higher dose and Helicobacter pylori-positive individuals needed only about 20% of the dose to achieve a given increase in mean 24-h intragastric pH. The present meta-analysis provides quantitative estimates on clinical potency of individual PPIs that may be helpful when switching between PPIs and for assessing the cost-effectiveness of specific PPIs. However, our estimates must be viewed with caution because only a limited dose range has been tested and not exactly the same study conditions were applied for the different substances.

Variation in the human genome is a most important cause of variable response to drugs and other xenobiotics. Susceptibility to almost all diseases is determined to some extent by genetic variation. Driven by the advances in molecular biology, pharmacogenetics has evolved within the past 40 years from a niche discipline to a major driving force of clinical pharmacology, and it is currently one of the most actively pursued disciplines in applied biomedical research in general. Nowadays we can assess more than 1,000,000 polymorphisms or the expression of more than 25,000 genes in each participant of a clinical study at affordable costs. This has not yet significantly changed common therapeutic practices, but a number of physicians are starting to consider polymorphisms, such as those in CYP2C9, CYP2C19, CYP2D6, TPMT and VKORC1, in daily medical practice. More obviously, pharmacogenetics has changed the practices and requirements in preclinical and clinical drug research; large clinical trials without a pharmacogenomic add-on appear to have become the minority. This review is about how the discipline of pharmacogenetics has evolved from the analysis of single proteins to current approaches involving the broad analyses of the entire genome and of all mRNA species or all metabolites and other approaches aimed at trying to understand the entire biological system. Pharmacogenetics and genomics are becoming substantially integrated fields of the profession of clinical pharmacology, and education in the relevant methods, knowledge and concepts form an indispensable part of the clinical pharmacology curriculum and the professional life of pharmacologists from early drug discovery to pharmacovigilance. peerReviewed

Previous reports have indicated that administration of the calcium antagonist diltiazem results in major changes in the pharmacokinetics of cyclosporin A (CyA). A new clinical trial was undertaken in 22 renal transplant patients receiving a constant dose of cyclosporin to further explore this interaction. Coadministration of diltiazem for one week produced an increase in the blood concentration of CyA and its metabolites 17 and 18 in almost all patients, but no increase in CyA metabolites 1 and 21. The mean whole blood CyA trough level determined by HPLC rose from 117 ng.ml-1 to 170 ng.ml-1 after one week on diltiazem, and the mean trough level of metabolite 17 rose similarly from 184 ng.ml-1 before to 336 ng.ml-1. Based on experiments with microsomes from human liver the effect of diltiazem was due to noncompetitive inhibition of CyA-metabolism by diltiazem, and the increased concentration of metabolite 17 might have been due to stronger inhibition of its secondary metabolism steps.

Enantiomerically pure drugs and genotyping are promising approaches to achieve optimization in antidepressant therapy. Mirtazapine is a mixed noradrenergic serotoninergic antidepressant used as a racemate. We analyzed pharmacokinetics of its enantiomers in relation to CYP2D6 genotype and in relation to its adverse effects. Mirtazapine was enantioselectively absorbed from the gut with a rate constant of 0.2 min-1 for S+, but 0.08 min-1 for R- mirtazapine. Kinetics of R- mirtazapine was only marginally dependent on CYP2D6 genotype, but total clearance of the S+ enantiomer were 1.3, 2.3, and 3.4 L min-1 in poor, extensive, and ultrarapid metabolizers of CYP2D6 substrates with apparent substantial first-pass metabolism in rapid and ultrarapid metabolizers. Mirtazapine effects on heart rate and blood pressure correlated much more strongly with R- then with S+ concentrations, whereas sedation correlated similarly with both enantiomers. At least concerning some adverse effects, it might be worthwhile to study further mirtazapine enantiospecifically.

Pharmacogenetics, one of the fields of clinical pharmacology, studies how genetic factors influence drug response. If hereditary traits are taken into account appropriately before starting drug treatment, the type of drug and its dosage can be tailored to the individual patient's needs. Today, the relationships between dosage requirements and genetic variations in drug-metabolizing enzymes such as cytochrome P450 (CYP) 2D6, CYP2C9, and CYP2C19 or in drug transporters such as p-glycoprotein (ABCB1) and OATP-C (SLC21A6) are substantiated best. A standard dose will bring about more adverse effects than usual if enzymatic activity is lacking or feeble. Sometimes, however, therapeutic response might be better because of higher concentrations: proton pump inhibitors for eradication of Helicobacter pylori are more efficacious in carriers of a deficient CYP2C19 variant. In some cases, genetic tests can help distinguish between responders and nonresponders of a specific drug treatment, and genotype-based dosage is possible.

Individual differences in the effect and side effect of drugs are partly due to genetic factors (genetic polymorphisms). The responsible polymorphisms lie in genes encoding for drug metabolism and transport but also in direct and indirect drug targets. While genetic variants in pharmacokinetic structures exert effects on drug efficacy via the differences in drug exposure, polymorphisms in drug targets can directly affect clinical efficacy and may lead to a broad variation spectrum between inefficacy and severe side effects. However, at present, our knowledge on genetic variants in drug targets is less detailed than the knowledge on pharmacogenetic variability within drug metabolism. A goal of pharmacogenetic diagnostics implemented in clinical practice is to better predict the individual drug effects on the basis of molecular-genetic profiles. Therapy recommendations can be given as dose adjustments, in particular in the case of polymorphisms of drug metabolizing enzymes which will lead to less variable drug concentrations. At present there are few examples of the application of pharmacogenetic tests in Germany in order to improve and individualize drug therapy. The reasons for this are multifold. On the one hand it is due to the limited awareness of pharmacogenetics; on the other hand it may be due to the lack of fast and economical availability of the appropriate laboratory tests. The most important reason, however, may be that most results of pharmacogenetic research are so far not translated into therapeutically usable conclusions and therapy recommendations. Thus, testing for a genotype without concrete consequences for the drug therapy of an individual patient does not make sense. Pharmacogenetic research, thereby, stands in many cases at the threshold to clinical applicability and in many cases, for instance for the genotyping for thiopurine methyltransferase polymorphisms prior to azathioprine therapy or of dihydropyrimidine dehydrogenase polymorphisms prior to treatment with 5-fluorouracil, as well as for diagnostics of CYP2D6 before therapy with certain tricyclic antidepressants and neuroleptics, one would ask already today whether a such drug therapy is still responsible without pharmacogenetic diagnostics.

Finding predictors of the response to antidepressant therapy is a major goal of molecular psychiatry. The genes encoding the serotonin (SERT) and dopamine (DAT1) transporters are among the possible candidate genes modulating an individual's antidepressant response. In a naturalistic prospective cohort study with a total of 190 fully assessed patients, improvement of depression symptoms during the 3 weeks following initiation of antidepressant therapy was recorded using the 21-item Hamilton Depression Rating Scale (HDRS). The SLC6A3 3' UTR 40-bp variable number of tandem repeats (VNTR) and the SLC6A4 5' 44-bp insertion/deletion polymorphism were analyzed by polymerase chain reaction. There was a significantly smaller number of rapid responders among homozygous carriers of the DAT1 9-repeat allele (9/9) than among heterozygous (9/10) and homozygous (10/10) carriers of the 10-repeat allele (19 versus 37 versus 52%, respectively, P=0.0037). Median decline in HDRS score was 35, 40, and 52% in patients with the 9/9, 9/10, and 10/10 genotypes, respectively (P=0.013). The effect was found in all classes of medications (selective serotonin reuptake inhibitors (SSRIs), tricyclics, mirtazapine, venlafaxine) and statistically significant also within the subgroup of patients having received SSRIs. The serotonin promoter insertion/deletion genotype had no effect in the entire study group, but there was an insignificant trend of better response in the l/l and l/s carriers who received SSRIs or mirtazapine. In conclusion, the dopamine transporter VNTR polymorphism influenced rapid response to antidepressant therapy. Compared with homozygous carriers of the 10-repeat allele, carriers of the 9/10 genotype had an odds ratio (OR) calculated by logistic regression analysis of 1.6 (95% CI 0.8-3.2) and carriers of the 9/9 genotype had an OR of 6.0 (1.5-24.4) for no or poor response. Further studies are required to confirm this clinical association and to elucidate the underlying mechanisms.

Genetische Variabilitat zwischen Individuen fuhrt zu betrachtlichen Unterschieden im Metabolismus und in der Elimination von Antidepressiva. Auf Seiten der Pharmakokinetik sind genetische Polymorphismen bereits lange bekannt und gut untersucht. Auf der pharmakodynamischen Seite wurden viele genetische Varianten beschrieben und in Assoziationsstudien untersucht, jedoch sind die Ergebnisse meist widerspruchlich und haufig nicht repliziert. Die Rolle von genetischen Varianten in Strukturen des serotonergen oder adrenergen Systems fur die Therapieresponse ist derzeitig noch nicht vorhersagbar. Pharmakogenetische Diagnostik wird es in Zukunft erlauben, individuelle Genotypen oder Genprofile zu bestimmen und in die Therapie mit einzubeziehen.

The pharmacokinetics and effect of antidepressants are influenced by genetic factors. Modern methods of genotyping allow fast and inexpensive identification of genetic variants and thus can be used in clinical diagnostics to improve the tolerance to drug therapy. Numerous studies have investigated the significance of genetic variants in drug-metabolizing enzymes, drug and natural substrate transporters, neurotransmitter receptors, and molecules involved in signal transduction. While the interindividual differences in oral clearance, half-life, and bioavailability caused by genetic variants in the cytochrome P450 liver enzymes can be overcome by individual adjustment of dosage according to certain genotypes, the effects of genetic variants in antidepressive target structures are more difficult to translate into clinical recommendations. This article gives an overview of the currently available literature and points to situations in which the determination of pharmacogenetic variants might change drug therapy or therapeutic strategies for the individual patient. Dose adjustments for common antidepressant drugs based upon differences in pharmacokinetic parameters caused by genetic variability will be given.

Since public acceptance of pharmacogenetic testing will largely influence their implementation in routine medical care, common implications of pharmacogenetic testing from patients', physicians' and scientists' perspective are reviewed.Broad literature review (MEDLINE; MeSH terms: Pharmacogenetics, Delivery of Health Care, Ethics, Attitude, Patient Acceptance of Health Care) of empirical and theoretical studies describing psychological, family-related, social, and ethical consequences of pharmacogenetic testing to describe relevant aspects for further empirical studies.Apart from anticipated benefit, acceptance of pharmacogenetic testing might be influenced by the following: Expectation of negative psychosocial consequences, fear of discrimination or violation of privacy. Due to its great complexity, understanding of test results and explanation of their impact pose new challenges for physician-patient relations. Since most studies are conceptual, empirical studies exploring attitudes of patients/physicians and determining medical as well as economic value of pharmacogenetic testing are imperative.

The effect of cytochrome P450 (CYP) 2C9 polymorphisms on the stereoselective biotransformation of the oral anticoagulant phenprocoumon (PPC) to inactive, monohydroxylated metabolites was studied in vitro and in vivo. In human liver microsomes, the (S)-7-hydroxylation--being the major metabolic pathway--was significantly compromised in a gene-dose-dependent manner in samples expressing the CYP2C9*2 or CYP2C9*3 allele. The CYP2C9*3/*3 genotype corresponded to an almost fourfold lower (S)-7-hydroxylation rate than CYP2C9*1/*1 (wild-type). The intrinsic clearance of human recombinant CYP2C9*2 and CYP2C9*3 for the (S)-7-hydroxylation was 28.9 and 50.9% lower than of CYP2C9*1, respectively. The area under the plasma concentration-time curve (AUC) of PPC metabolites after oral intake of 12 mg racemic PPC was significantly lower in volunteers expressing the CYP2C9*2 or CYP2C9*3 allele. Increasing plasma AUC metabolic ratios (parent compound/metabolite) in CYP2C9*2 and CYP2C9*3 variant allele carriers were found for each hydroxylation reaction and the CYP2C9*3/*3 genotype corresponded to an about 10-fold higher metabolic ratio of PPC (S)-7-hydroxylation relative to CYP2C9*1/*1. CYP2C9 polymorphisms cause a markedly compromised PPC (S)-7-hydroxylation. However, PPC metabolism appears overall less influenced by CYP2C9 genotype compared with other oral anticoagulants and it may thus be a valuable alternative for therapeutic anticoagulation of patients expressing CYP2C9 variant alleles.

Objective: To assess whether polymorphisms in the dopamine receptor genes and in the dopamine transporter gene ( DAT ) are predictors of adverse effects of l -dopa. Methods: A retrospective noninterventional study with 183 patients with PD was conducted. Nine polymorphisms of the dopamine D2 receptor ( DRD2 ), two of the dopamine D3 receptor ( DRD3 ), three of the dopamine D4 receptor ( DRD4 ), and one variable number of tandem repeats (VNTR) of the DAT were studied. The entire coding and promoter regions of the DRD2 gene of 48 patients with early and severe appearance of adverse effects from l -dopa treatment and of eight never-afflicted patients were sequenced. Results: The polymorphisms of DRD2 , DRD3 , and DRD4 were not associated with the risk to develop adverse effects of l -dopa. However, patients with psychosis or dyskinesia carried the nine copy allele 40–bp VNTR of the DAT more frequently than nonafflicted patients (60.0 vs 36.8%, p = 0.008; and 54.7 vs 32.9%, p = 0.006). Sequencing of the DRD2 gene revealed no new mutation, with the exception of one silent mutation in exon 6. Conclusions: Genetic variations of the DRD2 , DRD3 , and DRD4 do not influence the occurrence of l -dopa-induced adverse effects. However, the nine copy allele 40–bp VNTR of the DAT is a predictor for the occurrence of psychosis or dyskinesia in l -dopa-treated patients.

Es gibt Anhaltspunkte, dass Frauen von einer Reihe von Arzneimittelnebenwirkungen haufiger und schwerer betroffen sind als Manner. Die Arzneitherapie einiger Erkrankungen scheint bei Frauen weniger effizient zu sein als die entsprechende Therapie bei Mannern. Nach einigen Erhebungen sind Frauen bis zu 3-mal haufiger von Arzneimittelnebenwirkungen betroffen als Manner [1,2,5].

Aims Concentrations in the cerebrospinal fluid (CSF) are a useful approximation to the effect site for drugs like morphine. However, CSF samples, are available only in rare circumstances. If they can be obtained they may provide important insights into the pharmacokinetics/pharmacodynamics of opioids. Methods Nine neurological and neurosurgical patients (age 19–69 years) received 0.5 mg kg−1 morphine sulphate pentahydrate as an intravenous infusion over 30 min. Plasma and CSF were collected for up to 48 h. Concentration time-course and interindividual variability of morphine (M), morphine-3-glucuronide (M3G) and morphine-6 glucuronide (M6G) were analysed using population pharmacokinetic modelling. Results While morphine was rapidly cleared from plasma (total clearance = 1838 ml min−1 (95% CI 1668, 2001 ml min−1)) the glucuronide metabolites were eliminated more slowly (clearance M3G = 44.5 ml min−1 (35.1, 53.9 ml min−1), clearance M6G = 42.1 ml min−1 (36.4, 47.7 ml min−1)) and their clearance could be described as a function of creatinine clearance. The central volumes of distribution were estimated to be 12.7 l (11.1, 14.3 l) for morphine. Transfer from the central compartment into the CSF was also rapid for M and considerably slower for both glucuronide metabolites. Maximum concentrations were achieved after 102 min (M), 417 min (M3G) and 443 min (M6G). A P-glycoprotein exon 26 polymorphism previously found to be linked with transport activity could be involved in CSF accessibility, since the homozygous mutant genotype was associated (P

This review aimed to provide distinct dose recommendations for antidepressants based on the genotypes of cytochrome P450 enzymes CYP2D6 and CYP2C19. This approach may be a useful complementation to clinical monitoring and therapeutic drug monitoring.Our literature search covered 32 antidepressants marketed in Europe, Canada, and the United States. We evaluated studies which had compared pharmacokinetic parameters of antidepressants among poor, intermediate, extensive and ultrarapid metabolizers.For 14 antidepressants, distinct dose recommendations for extensive, intermediate and poor metabolizers of either CYP2D6 or CYP2C19 were given. For the tricyclic antidepressants, dose reductions around 50% were generally recommended for poor metabolizers of substrates of CYP2D6 or CYP2C19, whereas differences were smaller for the selective serotonin reuptake inhibitors.We have provided preliminary average dose suggestions based on the phenotype or genotype. This is a first attempt to apply the new pharmacogenetics to suggest dose-regimens that take the differences in drug metabolic capacity into account.

The role of hereditary polymorphisms of the arylamine N-acetyltransferase 1 (NAT1) gene in the etiology of urinary bladder cancer is controversial. NAT1 is expressed in the urothelium and may O-acetylate hydroxyl amines, particularly in subjects with low NAT2 activity. Thus, NAT1 polymorphisms may affect the individual bladder cancer risk by interacting with environmental factors (smoking and occupational risks) and by interacting with the NAT2 gene. We studied the frequencies of the NAT1 haplotypes *3, *4, *10, *11, *14, *15, *17, and *22 in 425 German bladder cancer patients and 343 controls by PCR-RFLP. NAT1*10 allelic frequency was lower in bladder cancer patients (15.1%) compared with controls (20.4%; P = 0.012). Genotypes that included NAT1*10 were significantly less frequent among the cases (odds ratio adjusted for age, gender, and smoking, 0.65; 95% confidence interval, 0.46-0.91; P = 0.013). Two subtypes of NAT1*11 were detected: *11A (-344T, -40T, 445A, 459A, 640G, and 1095A) and *11C (-344T, -40T, 459A, 640G, and 1095A). The allele frequency of NAT1*11 was 4.3% in the cases versus 3.9% in the controls. The rare low-active NAT1*14A was overrepresented in the cases (P = 0.026). With regard to the NAT2 genotype, our data showed: (a) a partial linkage of NAT1*10 to NAT2*4; (b) a clear underrepresentation of NAT1*10 genotypes among rapid NAT2 genotypes in the cases studied (odds ratio, 0.39; 95% confidence interval, 0.22-0.68; P = 0.001), and (c) a gene-gene-environment interaction. NAT2*slow/NAT1*4 genotype combinations with a history of occupational exposure were 5.96 (2.96-12.0) times more frequent in cancer cases than in controls without risk occupation (P0.0001). Hence, our data suggest that individuals provided with NAT2*4 and NAT1*10 are at a significantly lower risk for bladder cancer, particularly when exposed to environmental risk factors.

The pathomechanisms of most drug-induced agranulocytoses are unclear; however, there are some studies pointing to genetic determinants. Some drug-induced agranulocytoses such as clozapine-induced agranulocytosis (CA) may be regarded as an idiosyncratic drug reaction because of its preclinical and clinical characteristics. To study some aspects of the genetic background of CA further, polymorphisms of specific metabolizing enzyme systems of clozapine were examined. Thirty-one schizophrenic patients with CA and 77 schizophrenic comparison subjects without this adverse effect underwent genotyping of a recently discovered G -463 A polymorphism of myeloperoxidase (MPO) gene and cytochrome P4502D6. Neither the MPO mutation nor specific genotypes of cytochrome P4502D6 were associated with CA. Both were equally distributed among CA patients and controls. Thus, our data suggest lack of evidence of an association of CA and genetically variable activity of these specific drug metabolizing enzymes; however, this may be due to statistical reasons only. Thus, further studies with greater CA samples are necessary to draw final conclusions about these genetically based hypotheses.

The role of flavin containing monooxygenases (FMO) on the disposition of many drugs has been insufficiently explored. In vitro and in vivo tests are required to study FMO activity in humans. Benzydamine (BZD) N-oxidation was evaluated as an index reaction for FMO as was the impact of genetic polymorphisms of FMO3 on activity.BZD was incubated with human liver microsomes (HLM) and recombinant enzymes. Human liver samples were genotyped using PCR-RFLP.BZD N-oxide formation rates in HLM followed Michaelis-Menten kinetics (mean Km = 64.0 microM, mean Vmax = 6.9 nmol mg-1 protein min-1; n = 35). N-benzylimidazole, a nonspecific CYP inhibitor, and various CYP isoform selective inhibitors did not affect BZD N-oxidation. In contrast, formation of BZD N-oxide was almost abolished by heat treatment of microsomes in the absence of NADPH and strongly inhibited by methimazole, a competitive FMO inhibitor. Recombinant FMO3 and FMO1 (which is not expressed in human liver), but not FMO5, showed BZD N-oxidase activity. Respective Km values for FMO3 and FMO1 were 40.4 microM and 23.6 microM, and respective Vmax values for FMO3 and FMO1 were 29.1 and 40.8 nmol mg-1 protein min-1. Human liver samples (n = 35) were analysed for six known FMO3 polymorphisms. The variants I66M, P135L and E305X were not detected. Samples homozygous for the K158 variant showed significantly reduced Vmax values (median 2.7 nmol mg-1 protein min-1) compared to the carriers of at least one wild type allele (median 6.2 nmol mg-1 protein min-1) (P0.05, Mann-Whitney-U-test). The V257M and E308G substitutions had no effect on enzyme activity.BZD N-oxidation in human liver is mainly catalysed by FMO3 and enzyme activity is affected by FMO3 genotype. BZD may be used as a model substrate for human liver FMO3 activity in vitro and may be further developed as an in vivo probe reflecting FMO3 activity.