Theophylline clearance: effect of marked obesity

Total body clearance (ClT) of theophylline was examined in 12 markedly obese patients and related to total body weight (TBW) and ideal body weight (IBW). Patients were infused with aminophylline continuously and evaluated at steady state. Total body clearances of theophylline were 29.5 +/- 7.8 ml/hr/kg TBW and 58.8 +/- 15.9 ml/hr/kg IBW. In patients with congestive heart failure (CHF) (N = 4) theophylline ClT was 19.7 +/- 1.9 ml/hr/kg TBW or 47.7 +/- 8.3 ml/hr/kg IBW while in those with no CHF (N = 8) clearance was 34.5 +/- 3.5 ml/hr/kg TBW or 64.3 +/- 16.2 ml/hr/kg IBW. Acute renal failure did not appear to alter theophylline ClT in two patients (one with and one without CHF). Mean theophylline ClT closely approximated that of a normal population when corrected for IBW, but there was a much stronger correlation between theophylline ClT and weight when corrected for TBW. Our data suggest that maintenance doses of theophylline in markedly obese patients with CHF should be based on a theophylline ClT of 19.7 ml/hr/kg TBW and of 34.5 ml/hr/kg TBW in those with no CHF.