Single-dose pharmacokinetics of nefazodone in healthy young and elderly subjects and in subjects with renal or hepatic impairment

The single-dose pharmacokinetics of nefazodone (NEF) and its metabolites hydroxynefazodone (HO-NEF) and m-chlorophenylpiperazine (mCPP) were examined in 12 healthy younger subjects less than or equal to 55 years of age (YNG), 12 elderly subjects greater than or equal to 65 years of age (ELD), 12 patients with biopsy proven hepatic cirrhosis (HEP) and 12 patients with moderate renal impairment (REN), Cl-CR 20 - 60 ml . min(-1). The study was of parallel group design, with each of the four subject groups receiving escalating single oral doses of 50, 100 and 200 mg of nefazodone at 1 week intervals. Serial blood samples for pharmacokinetic analysis were collected for 48 h following each dose and plasma samples were assayed for NEF, HO-NEF and mCPP by a validated HPLC method. Single oral doses up to 200 mg of nefazodone were well tolerated by all subjects. Maximum plasma levels of NEF and HO-NEF were generally attained within 1 h after administration of nefazodone. HO-NEF and mCPP plasma levels were about 1/3 and < 1/10 those of NEF, respectively. There were no apparent gender-related pharmacokinetic differences in any group of subjects. NEF and HO-NEF pharmacokinetics were dose dependent in all four subject groups, a super-proportional increase in AUC and an increase in t(1/2) with increasing dose was obtained, indicative of nonlinear pharmacokinetics. Relative to normal subjects, elderly and cirrhotic subjects exhibited increased systemic exposure to NEF and HO-NEF, as reflected by AUC, at all doses of nefazodone; subjects with moderate renal impairment did not. Elderly and cirrhotic patients may require lower doses of NEF to achieve and maintain therapeutic effectiveness.