Theophylline clearance in obese patients in relation to smoking and congestive heart failure.

The effect of obesity on the total body clearance (Cltot) of theophylline was evaluated in nonsmokers and smokers with and without congestive heart failure (CHF). The obese patients were compared with similar nonobese subjects with regard to age, sex, and disease state. The total patient population numbered 150 adults. Cltot of theophylline, based on total body weight (TBW), averaged 0.60 +/- 0.20 ml/min/kg in obese nonsmokers and did not differ from the nonobese, nonsmoking group. In obese nonsmoking patients with CHF, Cltot based on TBW was 0.40 +/- 0.14 ml/min/kg, which was similar to Cltot values in nonsmoking CHF patients who were not obese. A trend toward a reduction in Cltot, based on TBW, as TBW increased, in nonsmoking patients with and without CHF, was observed. In contrast to the Cltot in nonsmokers, the Cltot of theophylline in obese smokers with and without CHF was similar to the Cltot values in nonobese populations only when based on ideal body weight. However, when compared with nonsmoking, nonobese patients, no differences were observed when Cltot was corrected for TBW. These findings suggest that theophylline maintenance dose can be based on TBW in obese patients who are smokers and nonsmokers (with and without CHF), using the average Cltot obtained for the nonsmoking patients with and without CHF.