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The overall objective of this thesis is to support successful clozapine treatment, by firstly expanding the knowledge on the predictability of early clozapine discontinuation, secondly investigating the necessity of clozapine discontinuation due to (intended) pregnancy, and thirdly expanding the knowledge on therapeutic drug monitoring (TDM) of clozapine in light of once-daily (QD) dosing and protein binding, as well as in light of possible pitfalls in the interpretation of these TDM results. In chapter 2.1 a prediction model was developed for unsuccessful clozapine treatment one year after the drug was first dispensed by a community pharmacy. Unsuccessful clozapine treatment was defined as the absence of current insurance claims for clozapine treatment 365 days after the index date. In 20.4% clozapine treatment was unsuccessful 1 year after the index date. Unsuccessful treatment was more common among outpatient starters than among inpatient starters. The number of variables needed to predict as much as 30% or 68% of the variability in unsuccessful clozapine treatment was too large for a simple prediction model. Disproportionality in case safety reports on adverse pregnancy outcomes between clozapine and other antipsychotics (OAP) used during pregnancy was determined in chapter 3.1. Overall, no signal of disproportionate reporting associating clozapine with the studied adverse pregnancy outcomes was found. Chapter 3.2 provides a critical appraisal of the available evidence related to the safety of clozapine for schizophrenia during pregnancy and lactation. Data on perinatal clozapine exposure are of limited quality and quantity. Data thus far do not support that clozapine is teratogenic, increases the risk of stillbirth, abortion, or foetal disorders, nor that it increases the risk of delivery complications or premature birth. Information about clozapine exposure through breast milk is scarce. In chapter 4.1, we determined whether the pharmacokinetics of clozapine and norclozapine with QD use are similar to twice-daily (BID) use. Dosing regimen did not affect any of the pharmacokinetic parameters of clozapine and norclozapine. Clozapine concentrations sampled in the morning with QD use are markedly different from its trough concentrations and higher than if the same daily dose had been used in two divided doses. The implications of this on clozapine’s therapeutic window at QD dosing is yet unknown. In chapter 4.2, we investigated whether protein binding of clozapine and norclozapine becomes saturated at higher concentrations. Secondly, we investigated the correlation between unbound clozapine and norclozapine fractions and alpha-1 acid glycoprotein concentrations. Clozapine and norclozapine concentrations correlated well with its unbound concentrations. The dosing regimen did not affect the relation between total clozapine and norclozapine concentrations and its unbound fractions. A moderate (clozapine) and small (norclozapine) correlation were found between AGP-concentrations and unbound fractions of clozapine and norclozapine. Chapter 4.3 describes the hurdles to be taken when developing a method for quantification of the unbound concentrations of clozapine and norclozapine in serum, using ultrafiltration (UF). This study demonstrates that the choice of the ultrafilter is a crucial part of the development of a method to measure unbound concentrations using UF. Adequate control of the factors influencing the NSA is essential, as well as factors influencing the stability of the protein-drug complex. The study in chapter 4.4 assessed whether clozapine concentrations measured in plasma collected with tubes containing ethylenediaminetetraacetic (EDTA) and lithium-heparin (LH) as anticoagulants are comparable to clozapine concentrations measured in serum. The use of LH-derived plasma samples for therapeutic drug monitoring of clozapine may lead to different clinical interpretations than when using serum samples. Therefore, interchangeable use of LH-derived plasma and serum samples to measure clozapine levels in clinical practice is not recommended. In chapter 5, the findings of this thesis were put into a broader perspective.

This thesis focuses on bioanalytical method development and validation of antileishmanial drugs amphotericin B, miltefosine, and paromomycin in human plasma and human skin tissue followed by clinical target site pharmacokinetic outcomes induced by these developed bioanalytical methods. Chapter 1 provides an overview of bioanalytical quantification methods of the most relevant antileishmanial used in human pharmacokinetic studies and clinical trials. It covers (liposomal) amphotericin B, miltefosine, paromomycin, pentamidine and pentavalent antimonials and summarizes sample preparation, calibration model, separation, and detection methods in various human matrices from identified published method validations and included future perspectives in the development of antileishmanial bioanalysis. Chapter 2 presents the development and validation of a modern bioanalytical method for the quantification of paromomycin in human plasma using ion-pair ultra-high performance liquid chromatography tandem mass spectrometry. It was the first bioanalytical assay that employed a stable isotope labelled internal standard in the quantification of paromomycin. The relevance of developing a sensitive method for the quantification of paromomycin in human plasma is discussed, furthermore its supporting role in clinical pharmacokinetic studies in patients suffering from visceral leishmaniasis in Kenya. Chapter 3 discusses and presents target-site bioanalytical methods for the quantification of antileishmanial drugs in human skin tissue. Chapter 3.1 provides an overview of existing skin tissue sample pre-treatment and homogenization techniques for quantification of pharmaceutical compounds. It discusses the advantages and disadvantages of certain homogenization techniques relative to the accuracy and recovery from skin tissue of the bioanalytical method. In chapter 3.2 the development and validation of a bioanalytical method for the quantification of miltefosine in human skin tissue is presented. It describes a detailed development of a homogenization method employing enzymatic digestion by collagenase A for human skin tissue sample processing. Furthermore, its clinical applicability to target-site pharmacokinetic studies in post-kala azar dermal leishmaniasis patients in Bangladesh is demonstrated. Chapter 3.3 focuses on the development and validation of a bioanalytical method for the quantification of amphotericin B in human skin tissue with a clinical application in post-kala azar dermal leishmaniasis patients in India. Finally, chapter 3.4 provides the development and validation of a bioanalytical method for the quantification of paromomycin in human skin tissue and a clinical application in a pharmacokinetic study in post-kala-azar dermal leishmaniasis patients in Sudan. Chapter 4 explores the pharmacokinetic outcomes of target-site pharmacokinetic studies employing human skin tissue data. Chapter 4.1 evaluates miltefosine pharmacokinetic and pharmacodynamic outcomes and presents the first skin tissue model characterizing the distribution of miltefosine from blood-based matrices to skin tissue from patients suffering from post-kala azar dermal leishmaniasis in India and Bangladesh. Chapter 4.2 presents a pharmacokinetic model for liposomal amphotericin B in both human plasma and skin tissue, exploring the target-site exposure and distribution of this antileishmanial drug based on clinical pharmacokinetic data of patients suffering from post-kala azar dermal leishmaniasis in India and Bangladesh. Chapter 5 summarizes and concludes the thesis and furthermore presents the authors’ views on future perspectives for the development of bioanalytical methods for antileishmanial drugs.

This thesis focuses on bioanalytical method development and validation of antileishmanial drugs amphotericin B, miltefosine, and paromomycin in human plasma and human skin tissue followed by clinical target site pharmacokinetic outcomes induced by these developed bioanalytical methods. Chapter 1 provides an overview of bioanalytical quantification methods of the most relevant antileishmanial used in human pharmacokinetic studies and clinical trials. It covers (liposomal) amphotericin B, miltefosine, paromomycin, pentamidine and pentavalent antimonials and summarizes sample preparation, calibration model, separation, and detection methods in various human matrices from identified published method validations and included future perspectives in the development of antileishmanial bioanalysis. Chapter 2 presents the development and validation of a modern bioanalytical method for the quantification of paromomycin in human plasma using ion-pair ultra-high performance liquid chromatography tandem mass spectrometry. It was the first bioanalytical assay that employed a stable isotope labelled internal standard in the quantification of paromomycin. The relevance of developing a sensitive method for the quantification of paromomycin in human plasma is discussed, furthermore its supporting role in clinical pharmacokinetic studies in patients suffering from visceral leishmaniasis in Kenya. Chapter 3 discusses and presents target-site bioanalytical methods for the quantification of antileishmanial drugs in human skin tissue. Chapter 3.1 provides an overview of existing skin tissue sample pre-treatment and homogenization techniques for quantification of pharmaceutical compounds. It discusses the advantages and disadvantages of certain homogenization techniques relative to the accuracy and recovery from skin tissue of the bioanalytical method. In chapter 3.2 the development and validation of a bioanalytical method for the quantification of miltefosine in human skin tissue is presented. It describes a detailed development of a homogenization method employing enzymatic digestion by collagenase A for human skin tissue sample processing. Furthermore, its clinical applicability to target-site pharmacokinetic studies in post-kala azar dermal leishmaniasis patients in Bangladesh is demonstrated. Chapter 3.3 focuses on the development and validation of a bioanalytical method for the quantification of amphotericin B in human skin tissue with a clinical application in post-kala azar dermal leishmaniasis patients in India. Finally, chapter 3.4 provides the development and validation of a bioanalytical method for the quantification of paromomycin in human skin tissue and a clinical application in a pharmacokinetic study in post-kala-azar dermal leishmaniasis patients in Sudan. Chapter 4 explores the pharmacokinetic outcomes of target-site pharmacokinetic studies employing human skin tissue data. Chapter 4.1 evaluates miltefosine pharmacokinetic and pharmacodynamic outcomes and presents the first skin tissue model characterizing the distribution of miltefosine from blood-based matrices to skin tissue from patients suffering from post-kala azar dermal leishmaniasis in India and Bangladesh. Chapter 4.2 presents a pharmacokinetic model for liposomal amphotericin B in both human plasma and skin tissue, exploring the target-site exposure and distribution of this antileishmanial drug based on clinical pharmacokinetic data of patients suffering from post-kala azar dermal leishmaniasis in India and Bangladesh. Chapter 5 summarizes and concludes the thesis and furthermore presents the authors’ views on future perspectives for the development of bioanalytical methods for antileishmanial drugs.

Opioids like morphine are commonly used to treat moderate or severe (cancer) pain. Importantly, the nonmedical use of prescription opioid analgesics can lead to opioid use disorder (OUD), which is associated with high morbidity and mortality rates. Of note, one can also initially become addicted to opioids without first being exposed to prescription opioids, through the use of illicitly obtained opioids. Opioid agonist treatment with methadone, buprenorphine(-naloxone), or slow-release morphine is the most common evidence-based treatment modality for individuals with OUD. Still, not all patients are successfully recruited or retained in these medication therapies. Thus, several countries, including the Netherlands, offer pharmaceutical-grade heroin (diacetylmorphine; diamorphine) as a maintenance treatment option for those individuals (heroin-assisted treatment or HAT). Interestingly, psychedelic substances, such as ibogaine, have been associated with the alleviation of several substance use disorders and may hold promise as potential treatments for OUD. Shifting from cancer-related analgesia and palliative care to pharmacological cancer treatment, we have also studied an inhibitor of poly(ADP-ribose) polymerases (PARPs) 1 and 2, two enzymes essential to normal DNA repair activities. PARP inhibitors have revolutionized the treatment of women with certain forms of advanced ovarian cancer. Presently, four PARP inhibitors are approved for clinical use, including niraparib, which is also currently being tested in multiple clinical trials for treatment of other types of cancer than ovarian, such as intracranial tumors. It is well established that (trans)membrane transporters play a role in drug disposition, therapeutic efficacy, and adverse drug reaction. Clinical-pharmacokinetic drug-drug interaction studies have also suggested that transporters often work together with drug-metabolizing enzymes in controlling drug absorption and elimination. Consequently, the effects of changes in transport activity due to environmental factors (e.g., drug interaction) or genetic variation should be considered. This is especially relevant when predicting potential changes in the systemic exposure of drugs, which can result in clinically relevant (pharmacodynamic) effects. In this dissertation, using various genetically modified mouse models, we investigated the impact of efflux (ABCB1 and ABCG2) and uptake transporters (OATP1A/1B/2B1) and cytochrome P450 3A (CYP3A) enzymes on the pharmacokinetics and tissue distribution of two opioids (morphine and heroin), the psychedelic compound ibogaine, and the PARP1/2 inhibitor niraparib, plus their relevant metabolites. Moreover, we further demonstrated the usefulness of knockout and humanized transgenic mouse models to investigate the pharmacological properties of the studied drug transporters and drug-metabolizing enzymes. All in all, we hope that the obtained knowledge from the studies described in this dissertation will prompt further (pre-)clinical research and help improve both the safety and efficacy profiles of the studied compounds, especially when considering a broader clinical application.

Opioids like morphine are commonly used to treat moderate or severe (cancer) pain. Importantly, the nonmedical use of prescription opioid analgesics can lead to opioid use disorder (OUD), which is associated with high morbidity and mortality rates. Of note, one can also initially become addicted to opioids without first being exposed to prescription opioids, through the use of illicitly obtained opioids. Opioid agonist treatment with methadone, buprenorphine(-naloxone), or slow-release morphine is the most common evidence-based treatment modality for individuals with OUD. Still, not all patients are successfully recruited or retained in these medication therapies. Thus, several countries, including the Netherlands, offer pharmaceutical-grade heroin (diacetylmorphine; diamorphine) as a maintenance treatment option for those individuals (heroin-assisted treatment or HAT). Interestingly, psychedelic substances, such as ibogaine, have been associated with the alleviation of several substance use disorders and may hold promise as potential treatments for OUD. Shifting from cancer-related analgesia and palliative care to pharmacological cancer treatment, we have also studied an inhibitor of poly(ADP-ribose) polymerases (PARPs) 1 and 2, two enzymes essential to normal DNA repair activities. PARP inhibitors have revolutionized the treatment of women with certain forms of advanced ovarian cancer. Presently, four PARP inhibitors are approved for clinical use, including niraparib, which is also currently being tested in multiple clinical trials for treatment of other types of cancer than ovarian, such as intracranial tumors. It is well established that (trans)membrane transporters play a role in drug disposition, therapeutic efficacy, and adverse drug reaction. Clinical-pharmacokinetic drug-drug interaction studies have also suggested that transporters often work together with drug-metabolizing enzymes in controlling drug absorption and elimination. Consequently, the effects of changes in transport activity due to environmental factors (e.g., drug interaction) or genetic variation should be considered. This is especially relevant when predicting potential changes in the systemic exposure of drugs, which can result in clinically relevant (pharmacodynamic) effects. In this dissertation, using various genetically modified mouse models, we investigated the impact of efflux (ABCB1 and ABCG2) and uptake transporters (OATP1A/1B/2B1) and cytochrome P450 3A (CYP3A) enzymes on the pharmacokinetics and tissue distribution of two opioids (morphine and heroin), the psychedelic compound ibogaine, and the PARP1/2 inhibitor niraparib, plus their relevant metabolites. Moreover, we further demonstrated the usefulness of knockout and humanized transgenic mouse models to investigate the pharmacological properties of the studied drug transporters and drug-metabolizing enzymes. All in all, we hope that the obtained knowledge from the studies described in this dissertation will prompt further (pre-)clinical research and help improve both the safety and efficacy profiles of the studied compounds, especially when considering a broader clinical application.

Vincristine induced peripheral neuropathy is the most common type of toxicity in patients using vincrstine. Vincristine is chemotherapeutic agent used in a diverse range of pediatric oncology treatment protocols. In this thesis we take a multidimensional view on the topic of vincristine induced peripheral neuropathy. We describe a validation study reporting on the validity of the Dutch translated version of the pediatric-modified total neuropathy score (ped-mTNS). Furthermore we report on the effects of vincristine induced peripheral neuropathy on quality of life during treatments. This showed that children with cancer and vincrstine induced peripheral neuropathy report a lower quality of life than children with cancer without vincristine induced peripheral neuropathy. Furthermore we report the outcomes of a randomized clinical trial studying the effect of administration duration (push injections versus one-hour infusions) of vincristine on the development of vincristine induced peripheral neuropathy. This trial reported no overall effect, but showed that when vincristine in concomitantly used with azole antifungals (which is generally avoided to their drug-drug interaction leading to an increase in vincristine induced peripheral neuropathy) in case of an invasive fungal infection requiring treatment next to vincristine, one-hour administration resulted in a significant reduced peripheral neuropathy compared to push injections. We also report on the outcomes of pharmacokinetics of vincrstine related to administration duration and describes genetic single nucleotide polymorphisms related to vincristine induced peripheral neuropathy. Finally, we describe the research protocol of an dose escalation trial with close toxicity monitoring in pediatric oncology patients in Kenyan patients.

The prevalence of ophthalmic abnormalities in horses is high, higher even than most people are aware of and this is why equine ophthalmology has increasingly become a focus of attention. Loss or impairment of vision of horses has negative consequences for performance, usability and welfare. This thesis comprises work that arose from research questions related to clinical (eye)problems encountered in daily equine practice and is divided in 3 parts. The first part is focused on unravelling of a genetic ophthalmic disease in the horse, namely distichiasis. In distichiasis, extra eyelashes grow from the tarsal glands on the eyelids. The treatment, long-term follow-up and the identification of the genomic regions associated with distichiasis have been described. Aspects of pharmacokinetics of corticosteroids, one of the most commonly used anti-inflammatories for the equine eye, have been addressed in the second part. The distribution into the different compartments of the equine eye of corticosteroid eye drops (dexamethasone and prednisolone) and oral corticosteroids (prednisolone) have been investigated. The third part focuses on anaesthesia, improving local anaesthetic techniques and adequate analgesia during and after (standing) surgical ophthalmic procedures in horses. This thesis sheds light on the genetic cause of an important ophthalmic disease like distichiasis in the horse, helps to improve evidence-based medical and surgical treatment, and provides a vision for further research and future perspectives for prevention and treatment of diseases of the equine eye.

The prevalence of ophthalmic abnormalities in horses is high, higher even than most people are aware of and this is why equine ophthalmology has increasingly become a focus of attention. Loss or impairment of vision of horses has negative consequences for performance, usability and welfare. This thesis comprises work that arose from research questions related to clinical (eye)problems encountered in daily equine practice and is divided in 3 parts. The first part is focused on unravelling of a genetic ophthalmic disease in the horse, namely distichiasis. In distichiasis, extra eyelashes grow from the tarsal glands on the eyelids. The treatment, long-term follow-up and the identification of the genomic regions associated with distichiasis have been described. Aspects of pharmacokinetics of corticosteroids, one of the most commonly used anti-inflammatories for the equine eye, have been addressed in the second part. The distribution into the different compartments of the equine eye of corticosteroid eye drops (dexamethasone and prednisolone) and oral corticosteroids (prednisolone) have been investigated. The third part focuses on anaesthesia, improving local anaesthetic techniques and adequate analgesia during and after (standing) surgical ophthalmic procedures in horses. This thesis sheds light on the genetic cause of an important ophthalmic disease like distichiasis in the horse, helps to improve evidence-based medical and surgical treatment, and provides a vision for further research and future perspectives for prevention and treatment of diseases of the equine eye.

A number of detoxification systems with broad substrate specificity, including drug transporters and drug-metabolizing enzymes, can protect the body from various toxins, and dramatically influence drug absorption, metabolism, distribution and elimination (ADME) processes, as well as in some cases physiological homeostasis. In Part I of this thesis, in view of the likely importance of the Carboxylesterase 2 enzyme in pharmacological and physiological processes, we generated and characterized several CES2-related genetically modified mouse models. We then demonstrated the value of these mouse models to investigate the pharmacological and physiological functions of the CES2 enzyme complex. In Part II of this thesis we explored and revealed the roles (especially in the blood-brain-barrier) of several drug transporters (ABCB1, ABCG2 and OATP1A/1B) and the drug-metabolizing CYP3A enzymes in pharmacokinetic behavior of several anti-tumor small-molecule inhibitors, as well as related drug-drug interaction effects. We believe that the obtained new mouse models and pharmacological and physiological insights will provide further useful information and support for improving drug discovery and development, and eventually clinical-therapeutic application regimens.

A number of detoxification systems with broad substrate specificity, including drug transporters and drug-metabolizing enzymes, can protect the body from various toxins, and dramatically influence drug absorption, metabolism, distribution and elimination (ADME) processes, as well as in some cases physiological homeostasis. In Part I of this thesis, in view of the likely importance of the Carboxylesterase 2 enzyme in pharmacological and physiological processes, we generated and characterized several CES2-related genetically modified mouse models. We then demonstrated the value of these mouse models to investigate the pharmacological and physiological functions of the CES2 enzyme complex. In Part II of this thesis we explored and revealed the roles (especially in the blood-brain-barrier) of several drug transporters (ABCB1, ABCG2 and OATP1A/1B) and the drug-metabolizing CYP3A enzymes in pharmacokinetic behavior of several anti-tumor small-molecule inhibitors, as well as related drug-drug interaction effects. We believe that the obtained new mouse models and pharmacological and physiological insights will provide further useful information and support for improving drug discovery and development, and eventually clinical-therapeutic application regimens.

De bloedhersenbarriere (BHB) is een belangrijke fysiologische entiteit, die vooral blijkt uit de eigenschap dat allerlei kleurstoffen en wateroplosbare farmaca niet direct de hersenen kunnen bereiken. Van verschillende kanten ontstond belangstelling voor de BHB met name rond een vraagstelling naar de effecten van kinkhoest-vaccinatie op het centraal zenuwstelsel. Bestanddelen van het B. pertussisvaccin blijken de permeabiliteit van de BHB te verhogen. Ook waren er vragen rond farmacontransport en rond het mechanisme van het ontstaan van leuco- myeloencehalopathie. Het gepresenteerde rapport is bedoeld een verkennend overzicht te zijn en bij relevante onderdelen is getracht enige conclusies te formuleren.

Er wordt een onderzoek beschreven naar verbetering van de therapeutische index van het cytostaticum cis-diamminedichloroplatinum (II) (cDDP) door cDDP te verpakken in liposomen. In twee in-vivo-experimenten is de verdeling van platina over weefsels en lichaamsvloeistoffen bij de rat bestudeerd na intraperitoneale toediening van cDDP verpakt in liposomen en IgG-liposomen. Toediening op deze wijze leidt tot een verlengde verblijftijd van het cytostaticum in de buikholte t.o.v. toediening van vrij cDDP. Opname van cDDP in lever, longen en milt wordt vergroot. Een derde in-vivo-experiment toont aan dat liposomen via de lymfen uit de buikholte verdwijnen.

In dit onderzoek zijn een aantal analytische, farmaceutische en farmacokinetische aspecten bestudeerd van het cytostaticum doxorubicine verpakt in twee verschillende typen liposomen. De fluid-state DXR-liposomen zijn instabiel gedurende de eerste zes maanden na bereiding m.b.t. farmaconlek en chemische stabiliteit van het DXR, maar de dispersie blijft stabiel m.b.t. de deeltjesgrootte van de liposomen. Na twaalf maanden is echter ook de stabiliteit m.b.t. de deeltjesgrootte verminderd. De gel-state DXR-liposomen zijn stabiel gedurende de eerste zes maanden. Na twaalf maanden is de stabiliteit m.b.t. de deeltjesgrootte echter afgenomen. De chemische stabiliteit is op dit tijdstip veel beter dan die van de fluid-state DXR-liposomen. In geen van beide typen DXR-liposomen is groei van aerobe bacterien aangetroffen. Het biologische deel is gericht op het verwerven van meer inzicht in het mechanisme achter de verbetering van de therapeutische index bereikt met DXR-liposomen. M.b.v. een scheidingsmethode om "vrij" DXR en liposoom-gebonden DXR in plasma van elkaar te scheiden, zijn "vrije" DXR-concentraties bepaald op verschillende tijdstippen na i.v. toediening.

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Dutch translation: RIVM report 267002001

In dit rapport wordt een gevoelige bepalingsmethode beschreven voor glycyrrhetinezuur in humaan plasma. De extractie van glycyrrhetinezuur uit plasma geschiedt met een vaste-fase extractie procedure met octadecylsilaan kolommen. De scheiding van glycyrrhetinezuur van plasmacomponenten gebeurt met hoge-druk vloeistofchromatografie. Door toepassing van geautomatiseerde "on-line" kolomschakeling met een voorscheiding van het vaste-fase extract over de voorkolom, kon de gevoeligheid en de selectiviteit verbeterd worden. De detectie geschiedt met UV bij 258 nm. De extractieopbrengst (+/- standaarddeviatie) van glycyrrhetinezuur uit plasma, op twee manieren bepaald, is (97,6 +/- 2,1)% respectievelijk (97,0 +/- 6,5)%. De precisie is 3-4% bij 1,1 mg/l. De methode is toepasbaar in een concentratiegebied van 0,03 tot 3,0 mg/l. De detectielimiet van glycyrrhetinezuur in bloed is 30 mug/l.

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In dit rapport wordt een gevoelige bepalingsmethode beschreven voor glycyrrhetinezuur in humaan plasma. De extractie van glycyrrhetinezuur uit plasma geschiedt met een vaste-fase extractie procedure met octadecylsilaan kolommen. De scheiding van glycyrrhetinezuur van plasmacomponenten gebeurt met hoge-druk vloeistofchromatografie. Door toepassing van geautomatiseerde "on-line" kolomschakeling met een voorscheiding van het vaste-fase extract over de voorkolom, kon de gevoeligheid en de selectiviteit verbeterd worden. De detectie geschiedt met UV bij 258 nm. De extractieopbrengst (+/- standaarddeviatie) van glycyrrhetinezuur uit plasma, op twee manieren bepaald, is (97,6 +/- 2,1)% respectievelijk (97,0 +/- 6,5)%. De precisie is 3-4% bij 1,1 mg/l. De methode is toepasbaar in een concentratiegebied van 0,03 tot 3,0 mg/l. De detectielimiet van glycyrrhetinezuur in bloed is 30 mug/l.

In dit rapport wordt een gevoelige methode beschreven voor de kwantitatieve bepaling van het diureticum indapamide in totaal-bloed-monsters. Na hemolyse van het bloedmonster wordt indapamide uit het hemolysaat geextraheerd met een vaste-fase extractiemethode. Kwantificering vindt plaats met behulp van omkeerfase vloeistofchromatografie met ultra-violet detectie bij 238 nm. De voorgestelde methode is gevoeliger dan de uit de literatuur bekende methodes. Concentraties tot 0,01 mg/l kunnen nog kwantitatief bepaald worden. Met behulp van de beschreven methode zijn de farmacokinetische profielen vastgesteld van indapamide in spontaan-hypertensieve ratten en in normotensieve controle ratten na eenmalige orale toediening van indapamide. In beide rattestammen werd indapamide snel in het maag-darmkanaal geabsorbeerd. Maximale concentraties van indapamide in bloed werden gevonden tussen 1 en 2 uur na toediening. Bij een dosis van 5 mg indapamide/kg lichaamsgewicht werden tot 24 uur na toediening in het bloed indapamide-concentraties aangetoond die hoger waren dan die welke bij de mens als therapeutisch worden beschouwd. In het bloed werd tevens een niet nader geidentificeerde indapamidemetaboliet aangetoond waarvan de concentratie vier uur na toediening van indapamide een maximum vertoonde.

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In dit rapport wordt een gevoelige methode beschreven voor de kwantitatieve bepaling in ratteserum van het vaatverwijdende middel isosorbide-dinitraat (ISDN) en zijn metabolieten isosorbide-2- mononitraat (2-ISMN) en isosorbide-5-mononitraat (5-ISMN). Deze stoffen worden uit serum geextraheerd met vaste-fase extractie met een HH-C18 fase. Kwantificering vindt plaats met behulp van capillaire gaschromatografie en elektron-capture detectie. Met de voorgestelde methode kunnen concentraties van ISDN en 2-ISMN tot mug/l serum en concentraties van 5-ISMN tot 5 mug/l serum kwantitatief worden bepaald, uitgaande van 100 mul serum. De extractie-opbrengst van ISDN (n=10) is (85,1 +- 7,6)%, van 2-ISMN (86,2 +- 7,2)% en van 5-ISMN (60,9 +_ 6,9)%. De precisie van ISDN van 5,0 tot 1329 mug/l is 5-9 %, van 2-ISMN van 2,2 tot 614 mug/l is 1 - 14 % en van 5-ISMN van 5 tot 3710 mug/l is 4 - 7 %.

In dit rapport wordt een gevoelige methode beschreven voor de kwantitatieve bepaling van het diureticum indapamide in totaal-bloed-monsters. Na hemolyse van het bloedmonster wordt indapamide uit het hemolysaat geextraheerd met een vaste-fase extractiemethode. Kwantificering vindt plaats met behulp van omkeerfase vloeistofchromatografie met ultra-violet detectie bij 238 nm. De voorgestelde methode is gevoeliger dan de uit de literatuur bekende methodes. Concentraties tot 0,01 mg/l kunnen nog kwantitatief bepaald worden. Met behulp van de beschreven methode zijn de farmacokinetische profielen vastgesteld van indapamide in spontaan-hypertensieve ratten en in normotensieve controle ratten na eenmalige orale toediening van indapamide. In beide rattestammen werd indapamide snel in het maag-darmkanaal geabsorbeerd. Maximale concentraties van indapamide in bloed werden gevonden tussen 1 en 2 uur na toediening. Bij een dosis van 5 mg indapamide/kg lichaamsgewicht werden tot 24 uur na toediening in het bloed indapamide-concentraties aangetoond die hoger waren dan die welke bij de mens als therapeutisch worden beschouwd. In het bloed werd tevens een niet nader geidentificeerde indapamidemetaboliet aangetoond waarvan de concentratie vier uur na toediening van indapamide een maximum vertoonde.

Om de risicoschatting van de aardappelglycoalkaloiden (GAs) alfa-solanine and alfa-chaconine te verbeteren zal er bij het RIVM een studie naar de farmacokinetiek van oraal toegediende GAs bij de mens uitgevoerd gaan worden. De beperkte informatie over de toxiciteit in relatie tot de GA-dosering maakt het noodzakelijk om eerst een voorstudie uit te voeren met als doel het vinden van een optimaal bloedafnameschema en een optimale GA-dosering voor een succesvolle hoofdstudie naar de farmacokinetiek van GAs. In de voorstudie kregen proefpersonen een GA-dosering in de vorm van een drankje toegediend (toegediende GA-doseringen: 0,20, 0,30, 0,50 or 0,70 mg/kg lichaamsgewicht) of ze kregen een portie aardappelpuree te eten, die een bekende hoeveelheid alfa-solanine en alfa-chaconine bevatte (toegediende GA-doseringen: 0,80, 0,95, 1,10 and 1,25 mg/kg lichaamsgewicht). Na elke toediening werden de farmacokinetiek en de mogelijke toxische effecten geevalueerd. Met behulp van de resultaten van de voorstudie kon een geschikt bloedafnameschema voor beide toedieningsvormen worden gevonden. Als GA-dosering in aardappelpuree, bleek een GA-dosering > 0,95 and < 1,00 mg/kg lichaamsgewicht het meest geschikt. Voor het drankje wordt verwacht dat een GA-dosering van 0,90 mg/kg lichaamsgewicht geschikt is voor de hoofdstudie. Door het uitvoeren van de hoofdstudie met deze doseringen zal er meer inzicht (in ieder geval voor alfa-chaconine) in de kinetiek van aardappel-GAs bij de mens worden verkregen.

Dit rapport bevat een erratum op de laatste pagina;English translation: RIVM report 267002002

Om de risicoschatting van de aardappelglycoalkaloiden (GAs) alfa-solanine and alfa-chaconine te verbeteren zal er bij het RIVM een studie naar de farmacokinetiek van oraal toegediende GAs bij de mens uitgevoerd gaan worden. De beperkte informatie over de toxiciteit in relatie tot de GA-dosering maakt het noodzakelijk om eerst een voorstudie uit te voeren met als doel het vinden van een optimaal bloedafnameschema en een optimale GA-dosering voor een succesvolle hoofdstudie naar de farmacokinetiek van GAs. In de voorstudie kregen proefpersonen een GA-dosering in de vorm van een drankje toegediend (toegediende GA-doseringen: 0,20, 0,30, 0,50 or 0,70 mg/kg lichaamsgewicht) of ze kregen een portie aardappelpuree te eten, die een bekende hoeveelheid alfa-solanine en alfa-chaconine bevatte (toegediende GA-doseringen: 0,80, 0,95, 1,10 and 1,25 mg/kg lichaamsgewicht). Na elke toediening werden de farmacokinetiek en de mogelijke toxische effecten geevalueerd. Met behulp van de resultaten van de voorstudie kon een geschikt bloedafnameschema voor beide toedieningsvormen worden gevonden. Als GA-dosering in aardappelpuree, bleek een GA-dosering > 0,95 and < 1,00 mg/kg lichaamsgewicht het meest geschikt. Voor het drankje wordt verwacht dat een GA-dosering van 0,90 mg/kg lichaamsgewicht geschikt is voor de hoofdstudie. Door het uitvoeren van de hoofdstudie met deze doseringen zal er meer inzicht (in ieder geval voor alfa-chaconine) in de kinetiek van aardappel-GAs bij de mens worden verkregen.

Dutch translation: RIVM report 267002001

niet beschikbaar

Eight groups of six male RIV:tox rats received oral and intravenous doses of benzo(a)pyrene (BaP) in a parallel study plan. Intravenously and orally four dose levels were administered. BaF was dissolved in soybean oil for oral administration, and in glycofurol for intravenous administration. The doses were such, that the absolute oral bioavailability could be calculated for two dose levels. The plasma pharmacokinetics of BaP after intravenous administration were described by a two-compartment model. The corresponding kinetic parameters were calculated. The elimination half-life of BaP was approx. 30-60 min. in the period 0-12 h after administration. Therefore, unchanged BaP will not accumulate after repeated administration, when it is administered once daily. The AUC values (area under the plasma concentration-time curve) increased more than proportionally with the oral or intravenous dose. The deviation from linearity was small for the doses used in this study. After oral administration multiple plasma concentration maxima were observed, which may be explained by an interaction of the oil solution with the bile. The absolute oral bioavailability of unchanged BaP was approx. 13% for a dose of 1 mg/kg and approx. 4% for a dose of 5 mg/kg. This does not mean, that the absorption of BaP decreased with increasing doses, because the non-linear increase of the AUC values with the dose may be explained by saturation of metabolism. The kinetic parameters and the oral bioavailability were in the same range as found in the literature for other rat species.

Eight groups of six male RIV:tox rats received oral and intravenous doses of benzo(a)pyrene (BaP) in a parallel study plan. Intravenously and orally four dose levels were administered. BaF was dissolved in soybean oil for oral administration, and in glycofurol for intravenous administration. The doses were such, that the absolute oral bioavailability could be calculated for two dose levels. The plasma pharmacokinetics of BaP after intravenous administration were described by a two-compartment model. The corresponding kinetic parameters were calculated. The elimination half-life of BaP was approx. 30-60 min. in the period 0-12 h after administration. Therefore, unchanged BaP will not accumulate after repeated administration, when it is administered once daily. The AUC values (area under the plasma concentration-time curve) increased more than proportionally with the oral or intravenous dose. The deviation from linearity was small for the doses used in this study. After oral administration multiple plasma concentration maxima were observed, which may be explained by an interaction of the oil solution with the bile. The absolute oral bioavailability of unchanged BaP was approx. 13% for a dose of 1 mg/kg and approx. 4% for a dose of 5 mg/kg. This does not mean, that the absorption of BaP decreased with increasing doses, because the non-linear increase of the AUC values with the dose may be explained by saturation of metabolism. The kinetic parameters and the oral bioavailability were in the same range as found in the literature for other rat species.

De Nederlandse visteelt heeft nog niet de beschikking over toegestane diergeneesmiddelen, terwijl de noodzaak om bepaalde middelen te gebruiken in de praktijk bestaat. Deze middelen zijn met name: flumequine, mebendazole, oxolinezuur, oxytetracycline, praziquantel en trimethosulfmix. Wat op dit moment niet duidelijk is is de farmacokinetiek van deze middelen voor de vissoorten die in Nederland gekweekt worden. Deze informatie is van belang om te voorkomen dat residuen van de geneesmiddelen in voor consumptie bestemde visproducten terecht komen. Om meer inzicht te krijgen in bestaande farmacokinetische data voor de meest gebruikte middelen is een literatuuronderzoek uitgevoerd.

De Nederlandse visteelt heeft nog niet de beschikking over toegestane diergeneesmiddelen, terwijl de noodzaak om bepaalde middelen te gebruiken in de praktijk bestaat. Deze middelen zijn met name: flumequine, mebendazole, oxolinezuur, oxytetracycline, praziquantel en trimethosulfmix. Wat op dit moment niet duidelijk is is de farmacokinetiek van deze middelen voor de vissoorten die in Nederland gekweekt worden. Deze informatie is van belang om te voorkomen dat residuen van de geneesmiddelen in voor consumptie bestemde visproducten terecht komen. Om meer inzicht te krijgen in bestaande farmacokinetische data voor de meest gebruikte middelen is een literatuuronderzoek uitgevoerd.

Processes occuring in the liver are very important for the description of the kinetic behaviour of drugs and compounds present in food. Therefore this research was focussed on dispersion and distribution processes occuring in the rat liver. Polyethylene glycols were used as test compounds because they are mixtures of different oligomers and offer a set of molecules with different molecular weights and sizes. The aim was to study the influence of molecular size on the permeability of different oligomers of polyethylene glycol (PEG) in the isolated perfused rat liver. Furthermore, the feasibility of performing these studies with non-radioactive labelled PEGs was studied.

Processes occuring in the liver are very important for the description of the kinetic behaviour of drugs and compounds present in food. Therefore this research was focussed on dispersion and distribution processes occuring in the rat liver. Polyethylene glycols were used as test compounds because they are mixtures of different oligomers and offer a set of molecules with different molecular weights and sizes. The aim was to study the influence of molecular size on the permeability of different oligomers of polyethylene glycol (PEG) in the isolated perfused rat liver. Furthermore, the feasibility of performing these studies with non-radioactive labelled PEGs was studied.