Comparison of Propranolol and Sotalol Pharmacokinetics in Obese Subjects

Six obese subjects (mean +/- s.d. : 145.1 +/- 16.7% of ideal body weight) were randomly assigned to a single i.v. dose either of (+/-)-propranolol base (0.108 mg kg-1 of ideal body weight) or of (+/-)-sotalol base (1.06 mg kg-1 of ideal body weight). Each subject received the other drug 7 days later. Pharmacokinetic parameters were compared with those obtained previously in non-obese control subjects. In obese subjects, the pharmacokinetic data calculated for sotalol were comparable with those measured in controls (total body clearance = 9.4 +/- 2.9 L h-1; volume of distribution during the terminal phase = 79.8 +/- 19.8 L or 0.9 +/- 0.2 L kg-1; terminal half-life = 6.2 +/- 1.6 h). For propranolol, total clearance (44.3 +/- 15.9 L h-1) and volume of distribution (230.5 +/- 48.2 L or 2.7 +/- 0.7 L kg-1) were significantly less than control values. The terminal half-life (3.9 +/- 1.1 h), was not significantly increased. These results could be explained by altered tissue blood flow and a decreased metabolic capacity of the liver in obese subjects.