ISSN:
1432-1041
Keywords:
diazepam
;
ranitidine
;
pharmacokinetics
;
hydroxycorticosteroids
;
hepatic enzymes
;
interaction
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Medicine
Notes:
Summary In 6 healthy volunteers the steady state pharmacokinetics of diazepam (5 mg p.o. once daily) was investigated in a randomized cross-over study with and without concomitant doses of ranitidine (150 mg bid). Following the last dose of diazepam on Day 10 of each part of the study, the plasma concentrations of diazepam were monitored for one dosing interval plus the subsequent 2 days. In addition, urinary excretion of 6-β-hydroxycortisol and 17-hydroxycorticosteroids were measured, their ratio being taken as an indicator of hepatic enzyme activity. Coadministration of ranitidine significantly reduced (p〈0.03) the trough and steady state concentrations (mean ± SD) of diazepam (114±36 Vs 104±30 ng/ml and 170±55 Vs 125±36 ng/ml, respectively). Plasma protein binding of diazepam (98.5±0.3%) was not affected by ranitidine. The half-life of elimination of diazepam (42.5±13.5 h) did not change significantly but its apparent oral clearance (assuming complete absorption) was significantly increased (p〈0.005) by ranitidine, from 22.6±9.2 to 30.0±9.1 ml/min. Urinary excretion of 6β-OH-cortisol (p=0.029) and 17-OH-corticosteroids (p=0.041) were significantly elevated by ranitidine, but their ratio did not change. In addition, in 4 additional subjects the disposition of diazepam following a single intravenous dose of 0.1 mg/kg was not significantly altered by ranitidine. Thus, the lowered steady state concentration of diazepam is most likely due to diminished absorption caused by the concurrent administration of ranitidine. However, it may be more important clinically that, unlike cimetidine, ranitidine did not impair the hepatic elimination of diazepam.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00610055
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