Pharmacokinetics of ondansetron in patients with hepatic insufficiency.

Ondansetron is primarily eliminated via hepatic metabolism; thus, liver disease may affect its clearance. The pharmacokinetics of ondansetron in patients with different degrees of hepatic insufficiency (N = 12 with hepatic impairment, as categorized by Pugh's classification method) were assessed and the results compared with results for age- and gender-matched control subjects with normal liver function (n = 12). A secondary objective was to correlate the Pugh method of assessing hepatic impairment and quantitative metabolic markers used to assess hepatic function (antipyrine clearance and indocyanine green clearance) with changes in the pharmacokinetics of ondansetron. This was an open-label study in which 8 mg ondansetron was given orally and intravenously, following a randomized crossover design. Clearance of ondansetron was lower among patients with hepatic impairment that control subjects. After a single, oral dose of ondansetron, mean absolute bioavailability increased markedly with increased hepatic insufficiency (approaching 100% in the group with severe hepatic impairment versus 66% for control subjects). These data suggest that there is a reduced first-pass effect in patients with liver disease resulting in a higher AUC0-infinity. A correlation existed between clearance of ondansetron and decreased antipyrine clearance; a smaller correlation existed between ondansetron clearance and indocyanine green clearance. Mean percent of ondansetron bound to plasma proteins was significantly lower in patients with liver disease than in control subjects. None of the patients experienced any severe adverse reactions attributed to ondansetron. A reduction in the clearance of ondansetron is associated with increasing degrees of hepatic insufficiency; therefore, patients with severe hepatic impairment (Pugh score of > 9) should have their daily dose of ondansetron limited to 8 mg (or 0.15 mg/kg).

Comparison of quantitative methods to assess hepatic function: Pugh's classification, indocyanine green, antipyrine, and dextromethorphan.

STUDY OBJECTIVES: To compare three quantitative metabolic markers used to assess hepatic function, indocyanine green (ICG), a high-extraction marker; antipyrine, a low-extraction marker; and dextromethorphan, a P-450IID6 marker, with the clinically used Pugh's classification. DESIGN: Comparison of 12 healthy controls with 12 age- and sex-matched patients with different degrees of liver disease. SETTING: Research center in a university-affiliated teaching hospital. PATIENTS: The 12 patients had different degrees of liver disease: 4 mild (Pugh's score 6 or 7); 4 moderate (Pugh's score 8 or 9); and 4 severe (Pugh's score > or = 10). Each level had an equal number of men and women subjects. MEASUREMENTS AND MAIN RESULTS: Clearance of ICG detected mild alterations in hepatic function as efficiently as it did for moderate and severe impairment, but it lacked the specificity to distinguish among the classification groups. In contrast, antipyrine was effective in identifying moderate and severe hepatic impairment; however, its clearance was not reduced in mild liver disease. Pugh's classification appears to be a clinically useful method of assessing the global degree of hepatic impairment in patients with chronic disease, and there was a significant correlation between it and antipyrine clearance (r = 0.67, p = 0.0003) and ICG clearance (r = 0.86, p = 0.0001). Four of eight patients with a Pugh's score greater than 8 had a dextromethorphan metabolic ratio expression reflective of a poor metabolizer phenotype based on 0- to 4-hour urine collection, but only two of those eight patients were classified as poor metabolizers based on 4- to 12-hour urine collection. These percentages of poor metabolizers are substantially higher than for historical controls (8.5-10.4%) and most likely reflect a decrease in the P-450IID6 functional ability with progression of liver disease. However, due to small sample size and lack of knowledge of the patients' genotypes, these data are only suggestive. CONCLUSION: Pugh's classification appears to be a reliable indicator of the degree of chronic liver disease and could be employed as a drug development research classification tool; however, it does not replace quantitative metabolic markers, especially isozyme-specific markers.

Ranitidine does not alter adinazolam pharmacokinetics or pharmacodynamics.

Adinazolam is a triazolobenzodiazepine with anxiolytic and antidepressant activity. Adinazolam is metabolized extensively; the major metabolite, N-desmethyladinazolam (NDMAD), possesses significant pharmacologic activity. NDMAD is eliminated predominantly by renal excretion. Ranitidine, a histamine H2-receptor antagonist, is also excreted renally and may compete with NDMAD for renal secretion. The purpose of this study was to examine the effect of ranitidine on the pharmacokinetics and pharmacodynamics of adinazolam and NDMAD. In a randomized, cross-over study, 12 healthy male volunteers received 300 mg of ranitidine orally followed by 30 mg of adinazolam 1 hour later (treatment A), or adinazolam alone (treatment B). Pharmacodynamic alterations were assessed using card sorting, digit-symbol substitution, and short-term memory tests. Venous blood samples were obtained over 24 hours for analysis of adinazolam and NDMAD by high-performance liquid chromatography. Urine samples also were collected and analyzed for NDMAD. No significant difference in adinazolam oral clearance (1,149 vs. 1,135 ml/hr/kg) was noted between treatments (A vs. B, respectively). Furthermore, the renal clearance of NDMAD (196 vs. 198 ml/min) and the cumulative urinary excretion of NDMAD (% dose; 61.2 vs. 62.3) were not significantly different. Repeated-measures analysis of variance indicated no significant differences in psychomotor performance or short-term memory between treatments. Results suggest that ranitidine has no effect on adinazolam disposition, NDMAD renal clearance, or the central nervous system effects mediated by the drug.