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Aromatic hydroxylation of 5-phenyl-5-ethylhydantoin (PEH) has been investigated in humans. Single oral doses of S-PEH (247 mumol) were given to seven extensive and seven poor hydroxylators of mephenytoin. Urinary recovery of PEH and 5-(4-hydroxyphenyl)-5-ethylhydantoin (4-OH-PEH) indicated that all extensive metabolizer subjects excreted appreciable quantities of 4-OH-PEH, whereas all poor metabolizer subjects had only trace amounts of 4-OH-PEH in their urine. Four extensive metabolizer subjects received dual radiolabeled (S-[14C]PEH, R-[3H]PEH) pseudoracemic (494 mumol R-PEH, 494 mumol S-PEH) PEH and had serial urine and blood samples collected over 16 days. The urinary excretion rates of S-PEH and S-4-OH-PEH had half-lives of approximately 4.5 days whereas those of R-PEH and R-4-OH-PEH were approximately 10 days. The initial S/R ratio of 4-OH-PEH in urine was 14:1 whereas that of PEH was 1:1. Stereoselective hydroxylation in these four subjects was confirmed by the negligible recovery of 4-OH-PEH after oral administration of R-PEH (494 mumol). After racemic administration, the sum of S-and R-PEH plasma concentrations declined biexponentially with half-lives of the alpha- and beta-phases being consistent with the total plasma concentration reflecting the sum of the different rates of elimination of the two enantiomers. These results are consistent with the hypothesis that the same drug metabolizing enzymes are involved in the aromatic hydroxylation of S-mephenytoin and S-PEH.

During the period 1967 to 1971 an increase in the incidence of pulmonary hypertension of vascular origin (PHVO) was observed in Austria, Federal Republic of Germany, and Switzerland. Most patients had been given aminorex fumarate and a possible link was suspected. We therefore investigated the possibility of genetically — determined drug hydroxylation deficiencies (debrisoquine or mephenytoin type) in these patients as an explanation for the development of PHVO. Seventeen patients took 10 mg debrisoquine and 100 mg mephenytoin orally. Sixteen PHVO patients were classified as extensive metabolizers of debrisoquine with logarithmic metabolic ratios of -0.35±0.11 (mean±SEM), whereas one patient was a poor metabolizer with a logarithmic metabolic ratio of 1.82. For the mephenytoin hydroxylation sixteen patients with PHVO were extensive metabolizers, with logarithmic hydroxylation indices of 0.27±0.05. One poor metabolizer of mephenytoin had a logarithmic hydroxylation index of 1.59. Deficient hydroxylation of debrisoquine and mephenytoin was found in two different patients. The prevalence of poor metabolizers among patients with PHVO after aminorex fumarate was therefore approximately 9% for both debrisoquine and mephenytoin. This corresponds closely to the data of our reference population study where genetic debrisoquine and mephenytoin hydroxylation deficiencies occured independently, with a prevalence of 10% and 5% respectively. Thus, the normal prevalence of extensive drug hydroxylation phenotypes in patients with PHVO is not consistent with the hypothesis that the development of PHVO after aminorex fumarate might be related to a pharmacogenetically determined impairment of polymorphic drug oxidation.

Summary: The quantification of liver function is possible using the approach of salivary caffeine clearance. Hepatopathy sometimes complicates cystic fibrosis (CF), thus suggesting the use of this diagnostic tool in CF as well. Since in CF some compounds are poorly absorbed or abnormally metabolized, and the function of salivary glands or renal tubuli partly imparired, caffeine was measured in urine, blood, and saliva after a single oral dose of 3 mg/kg in CF patients. The urinary excretion rate of caffeine was normal in five CF patients. The caffeine levels in plasma or saliva, measured 4 to 5 h and 16 to 17 h after caffeine intake, were normal in 34 nonhepatopatic CF patients. The calculated salivary caffeine clearance was comparable in the 34 nonhepatopatic CF patients (1.88 × 0.46 ml/min/kg) and in the control group (1.88 × 0.44 ml/min/kg). In CF patients, no correlation was found between caffeine clearance and body weight, height, relative underweight, dosage of pancreatic enzymes, or Chrispin-Norman x-ray score. The salivary caffeine clearance was reduced in seven hepatopathic CF patients (1.32 × 0.63 ml/min/kg, p < 0.01): nevertheless, the salivary caffeine clearance was reduced (boundary line at 1.1 ml/min/kg) in three CF patients with proven liver cirrhosis but not in four with hepatosplenomegaly and altered liver tests. These data indicate an unaltered caffeine metabolism in CF and open the way for the use of this diagnostic procedure in CF and open the way for the use of this diagnostic procedure in CF as well. This test might be valuable in CF patients with clinical or laboratory findings suggesting liver involvement.

Dextromethorphan hydrobromide, 25 mg po, was given to 268 unrelated Swiss subjects to study urinary drug and metabolite profiles. Rates of O-demethylation yielding the main metabolite dextrorphan were expressed by the urinary dextromethorphan/dextrorphan metabolic ratio. We found a bimodal distribution of this parameter in our population study, which indicates that there are two phenotypes for dextromethorphan O-demethylation. The antimode at a metabolic ratio of 0.3 separated the poor metabolizer (PM; n = 23; prevalence of 9%) from extensive metabolizer (EM) phenotypes. Urinary output of dextrorphan was <6% of the dose in all PMs and was 50% in the 245 EMs. Pedigree analysis of 14 family studies revealed an autosomal-recessive transmission of deficient dextromethorphan O-demethylation. In these families, 37 heterozygous genotypes could be identified; however, through use of the urinary drug and metabolite analysis it was not possible to identify the heterozygous genotypes within the EM phenotype group. Co-segregation of dextromethorphan O-demethylation with debrisoquin 4-hydroxylation was also studied. Complete concordance of the two phenotypic assignments was obtained, with a Spearman rank correlation coefficient of rs= 0.78 (n = 62; P < 0.0001) for dextromethorphan and debrisoquin metabolic ratios. Presumably the two drug oxidation polymorphisms are under the same genetic control. Thus the innocuousness and ubiquitous availability of dextromethorphan render it attractive for worldwide pharmacogenetic investigations in man.

Inherited deficiency in mephenytoin hydroxylation was observed in a family study. It is important that the propositus was of the extensive metabolizer phenotype for the genetically controlled hydroxylation of debrisoquine. Thus, a genetic polymorphism of drug hydroxylation was suspected for mephenytoin. A population study of mephenytoin hydroxylation, combined with identification of extensive and poor debrisoquine hydroxylation phenotypes, was carried out in 221 unrelated normal volunteers. Twelve of them (5%) exhibited defective aromatic hydroxylation of mephenytoin, and 23 (10%) could be identified as poor metabolizers of debrisoquine. Amongst these 35 subjects with a drug hydroxylation deficiency, 3 (or 0.5%; 1 female, 2 males) displayed both defects simultaneously. A panel study of 10 extensive and 10 poor metabolizers of mephenytoin showed that the ability to perform aromatic hydroxylation of the demethylated mephenytoin metabolite nirvanol (5-phenyl-5-ethylhydantoin) was co-inherited with the mephenytoin hydroxylation polymorphism. Family studies suggested that poor metabolizer phenotypes of nirvanol and mephenytoin were most likely to have the homozygous genotype for an autosomal recessive allele of deficient aromatic drug hydroxylation. Intra-subject comparison of the debrisoquine and mephenytoin hydroxylation phenotypes in these subjects indicated that deficiency in the two drug hydroxylations occurred independently. Consequently, the co-inheritance of extensive and poor hydroxylation of mephenytoin and nirvanol, respectively, represents a new drug hydroxylation polymorphism in man.

Summary: The quantification of liver function is possible using the approach of salivary caffeine clearance. Hepatopathy sometimes complicates cystic fibrosis (CF), thus suggesting the use of this diagnostic tool in CF as well. Since in CF some compounds are poorly absorbed or abnormally metabolized, and the function of salivary glands or renal tubuli partly imparired, caffeine was measured in urine, blood, and saliva after a single oral dose of 3 mg/kg in CF patients. The urinary excretion rate of caffeine was normal in five CF patients. The caffeine levels in plasma or saliva, measured 4 to 5 h and 16 to 17 h after caffeine intake, were normal in 34 nonhepatopatic CF patients. The calculated salivary caffeine clearance was comparable in the 34 nonhepatopatic CF patients (1.88 × 0.46 ml/min/kg) and in the control group (1.88 × 0.44 ml/min/kg). In CF patients, no correlation was found between caffeine clearance and body weight, height, relative underweight, dosage of pancreatic enzymes, or Chrispin-Norman x-ray score. The salivary caffeine clearance was reduced in seven hepatopathic CF patients (1.32 × 0.63 ml/min/kg, p < 0.01): nevertheless, the salivary caffeine clearance was reduced (boundary line at 1.1 ml/min/kg) in three CF patients with proven liver cirrhosis but not in four with hepatosplenomegaly and altered liver tests. These data indicate an unaltered caffeine metabolism in CF and open the way for the use of this diagnostic procedure in CF and open the way for the use of this diagnostic procedure in CF as well. This test might be valuable in CF patients with clinical or laboratory findings suggesting liver involvement.

[1-Methyl-14C], [3-Methyl-14C] and [7-Methyl-14C] caffeine were used to investigate demethylation in control rats, and in rats pretreated with phenobarbital or 3-methylcholanthrene, by a14CO2-exhalation test. Compared to controls, pretreatment with phenobarbital did not enhance demethylation of any of the labelled caffeines. In contrast, induction by 3-methylcholanthrene, presumably of cytochrome P-448, resulted in highly significant increases in peak14CO2 exhalation rates,14CO2 disappearance constants and areas under the exhalation rate — time curves. Based on these results, [7-methyl-14C] and [3-methyl-14C] caffeine were chosen for assessing the feasibility of a caffeine breath test in man, using 5 normal volunteers and 2 patients with compensated liver cirrhosis.14CO2 exhalation curves in cirrhotics were clearly different from those in normal volunteers, being characterised by a slower rise and a lower specific activity of exhaled14CO2. Since the variability of the levels of the specific activity in subjects with normal livers suggested the influence of extraneous factors, a second group of normal volunteers, smokers and nonsmokers, was investigated. With either labels, the average14CO2 exhalation rate was doubled in smokers. From these studies in rats and preliminary results in man it is concluded that specifically labelled caffeine is a suitable and promising substrate for studying demethylation by breath analysis. Presumably, caffeine represents a safe and sensitive indicator of the activity of the cytochrome P-448 system.

Previous experimental work in animals has shown that the hepatic excretion of iodipamide and ioglycamide is subject to a transport maximum (TM). Doses in excess of this TM are largely excreted in the urine. In the present study the TM for man was estimated in three subjects with indwelling T-tubes: figures of 19–23 mg/minute for ioglycamide were obtained.It was thought that prolonged administration of contrast at levels slightly above the TM might have advantages in patients with impaired liver function. In obstruction the gradual excretion of contrast could improve the chances of filling the ducts completely, while in hepato-cellular disease the gall bladder might have time to concentrate the contrast. Ioglycamide was therefore given by slow overnight infusion, equivalent to 35 mg/minute, to patients in whom standard cholangiography had been unsuccessful. The overall success rate was 75 per cent with similar improvement in obstructive and hepatocellular disease.

The influence of stereoisomerism on pharmacokinetics and rates of hepatic drug metabolism was investigated in four dogs using the enantiomers of phenylethylhydantoin (PEH) as model substances. After single i.v. administration of 98 micromoles of the pure enantiomers per kg b.wt., concentrations were measured by gas-liquid chromatography. The l-form exhibited a longer plasma half-life (23.3 +/- S.E. 1.0 hour) than the d-form (16.3 +/- 1.0 hour, P less than .005). Volumes of distribution and renal clearances were practically identical. The differences in plasma half-lives of PEH were explained by stereoselectivity of hepatic hydroxylation: an approximately 10-fold differences was found in urinary excretion of their major metabolities, d- and l-hydroxyphenylethylhydantoin (HPEH). Furthermore, in bile 7.3 +/- 1.6 mumol of of d-HPEH were eliminated within the first 6 hours, whereas l-HPEH could not be detected. The preference in biliary output of d- compared with l-PEH is consistent with the idea that both hepatic uptake and microsomal hydroxylation of PEH contribute to the high degree of stereoselectivity. In view of similar extrahepatic, but different metabolic behavior of these enantiomers, they represent an interesting research tool for in vivo studies of drug metabolism: in otherwise identical conditions, two different rates of PEH hydroxylation may be studied.

The influence of ethanol on the fate of orally administered drugs which normally undergo a high presystemic elimination is as yet ill-defined. Experiments, therefore, were designed in four nonanesthetized dogs with mephenytoin as model compound. The drug was administered p.o. or i.v., and throughout an 8-hr period ethanol (100 mg kg-1 hr-1) or saline was infused according to a cross-over design. Concentrations of mephenytoin and its main metabolites, nirvanol and p-hydroxymephenytoin, were determined by gas-liquid chromatography. In experiments with oral mephenytoin administration and ethanol infusion, mephenytoin peak plasma concentrations were elevated by 87.0 +/- 15.2% (S.E.M.) (P less than .005, n = 4). Correspondingly, the average area under the plasma concentration time curve was increased to 229% of control (P less than .005). Ethanol also reduced metabolite formation; the area under the plasma concentration time curve for nirvanol was reduced by 40% (P less than .005). Urinary output of nirvanol was diminished to 51% and of p-hydroxymephenytoin to 73% (P less than .05, n = 12). It is concluded that drug ethanol interactions may be particularly prominent for orally administered drugs which normally are subject to a high presystemic elimination. This mechanism might be a clinically relevant cause for ethanol related drug toxicity.

Fasting plasma caffeine concentrations (FPCC) were measured in 86 outpatients being examined for suspected or known liver disease. Seven patients (8%) who avoided caffeine consumption had nonmeasurable FPCC; they were dropped from further consideration. The remaining 79 subjects were divided into 4 diagnostic groups: surgical shunt (n = 11); alcoholic, posthepatitic, or primary biliary cirrhosis (n = 29); miscellaneous liver disease (n = 23); and normal liver (n = 16). FPCC was highest (mean, 17.8 μmol/1) in the shunt group, followed by the cirrhosis (12.3), miscellaneous liver diseases (4.6), and normal liver (2.1) groups. FPCC seemed to reflect severity of functional impairment, further supported by highly significant correlations with quantitative liver function tests, such as aminopyrine breath test (Rs = -0.89; n = 66), indocyanine green disappearance (Rs = -0.85; n = 65), and galactose elimination capacity (Rs = -0.70; n = 75). A careful dietary history showed no significant difference in caffeine consumption among the groups. It is suggested that in regular coffee drinkers FPCC might serve as a simple and convenient guide to the severity of functional impairment in chronic liver disease.

Combined hemodynamic, functional, and angiographic studies were performed in 44 patients with cirrhosis of the liver. A statistically significant correlation (p = 0.02) was found between liver function as measured by galactose elimination capacity (GEC) and arterial perfusion of the liver. These data suggest a relationship between the amount of functioning liver parenchyma and the degree of arterial vascular supply.

Summary Individual liver function tests were compared in heterologously perfused liver, immediately after orthotopic transplantation and in the normal whole animal (pig).

Summary The amount and composition of produced bile were tested in 10 nonicteric and 6 icteric patients following operations on the biliary passages by means of a blockable balloon -T-drain. Water excretion and electrolyte content in both groups are in a quantitative relationship to the excreted bile salts. The flow of bile in the icteric patients is increased by additional excretion of a fluid rich in bicarbonate, originating presumably from the epithelia of the biliary passages.

Summary Under physiological perfusion conditions pig's liver can be preserved as a functioning organ almost indefinitely. Its functional capacity, proved in clinical use but limited in comparison with the intact animal, can be confirmed by accurate measurements of partial functions. It can, however, be shown from the example of bile formation that reduced function does not necessarily mean liver damage. It seems that the isolated organ is set new limits of performance.

Pharmacological studies on dog liver should often be related to quantitative light and electron microscopical findings obtained from liver biopsies. The purpose of this investigation was to study the application of stereological methods to liver biopsies of normal untreated dogs in order to obtain base-line data serving as standards for comparison with findings from pathological liver.

It could be demonstrated that intraportal infusion of prostaglandin A1(1 μg/min/100 g body wt.) in Wistar rats significantly increases bile flow. An analysis of the relationship between bile salt excretion and bile flow revealed that this choleresis is due to an increase in the bile salt independent fraction of bile.

A case of delayed biliary obstruction and cholangitis, occurring in the setting of chronic allograft rejection, 8 years after liver transplantation using the gallbladder-conduit, is presented. Extrahepatic biliary obstruction may be seen in the late follow-up of liver grafting and rejection phenomena may play a significant role in the development of such obstruction.