Lidocaine disposition in obesity.

Fourteen obese men (mean weight 124 +/- 8 kg (+/- standard error of the mean), percent ideal body weight (IBW) 169 +/- 10%), 11 obese women (96 +/- 6 kg; 174 +/- 11% IBW), 19 control men (69 +/- 1 kg; 93 +/- 2% IBW), and 12 control women (59 +/- 2 kg; 102 +/- 3% IBW), all of similar age and without clinical or laboratory evidence of cardiac or renal dysfunction, received a single 25-mg intravenous dose of lidocaine. Elimination half-life was markedly prolonged in obese compared with control men (2.69 +/- 0.2 vs 1.62 +/- 0.06 hour, p less than 0.001) and in obese compared with control women (2.95 +/- 0.1 vs 2.08 +/- 0.06 hour, p less than 0.01). This was not the result of a change in clearance (men, obese vs control: 1,427 +/- 117 vs 1,346 +/- 86 ml/min, difference not significant, [NS]; women: 1,089 +/- 83 vs 1,162 +/- 84 ml/min, NS), but rather of an increased absolute volume of distribution (Vd) in obese men (325 +/- 29 vs 186 +/- 12 liters, p less than 0.001) and obese women (264 +/- 20 vs 209 +/- 15 liters, p less than 0.025). Vd corrected for total body weight was unchanged in obesity for both men (2.67 +/- 0.22 vs 2.71 +/- 0.18 1/kg, NS) and women (2.88 +/- 0.31 vs 3.57 +/- 0.25, NS), suggesting that lidocaine Vd increases in parallel with body weight in both sexes. Because lidocaine clearance is determined mainly by hepatic blood flow, these findings suggest that extremes of body weight do not change hepatic blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)