The effect of roxatidine acetate and cimetidine on hepatic drug clearance assessed by simultaneous administration of three model substrates.

The effect of pretreatment for 7 days with either roxatidine acetate 75 mg twice daily or cimetidine 200 mg four times daily on the kinetics of antipyrine (AP), trimethadione (TMO) and indocyanine green (ICG) was studied in seven healthy, male, nonsmoking subjects. After pretreatment with cimetidine, the plasma clearances (CL) of AP and TMO were significantly lower and the elimination half-life (t1/2) of AP was significantly increased. The volumes of distribution (V) of AP and TMO were not affected. After roxatidine acetate, the pharmacokinetics of AP and TMO were unchanged. The cumulative renal excretion (% dose) and formation clearance of 3-hydroxymethyl-3-nor-antipyrine (NORA) were lowered by cimetidine treatment, but not following the administration of roxatidine acetate. ICG clearance was not changed significantly by either pretreatment. The results of this study show that roxatidine acetate does not impair the metabolism of three model substrates used to assess hepatic drug clearance.