Disposition of oxazepam in relation to age,sex, and cigarette smoking

Summary The kinetics of single 30-mg oral doses of oxazepam were determined in 22 male and nine female volunteers aged 20–86 years. Oxazepam plasma concentrations were measured in multiple plasma samples drawn during 36 h after each dose. Mean kinetic variables in males and females, respectively, were: elimination half-life, 7.5 and 8.5 h; volume of distribution, 0.96 and 1.17 l/kg; clearance, 1.48 and 1.70 ml/min/kg. Sex differences were not significant, nor were any of the kinetic variables significantly related to age. However, oxazepam clerance increased significantly with heavier cigarette smoking (r=0.48,p<0.01). Mean clearance in smokers (1.98 ml/min/kg) was significantly higher than in non-smokers (1.23 ml/min/kg,p<0.01). Thus, smoking is a more important determinant of oxazepam clearance than age or sex.Supported in part by Grant Oc 10/4 from the Deutsche Forschungsgemeinschaft, Bonn-Bad Godesberg, Federal Republic of Germany; and Grant MH-34223 from the United States Public Health Service