Effect of the surface area of activated charcoal on theophylline clearance

The effect of the surface area of activated charcoal on theophylline clearance was studied. Eight fasting, healthy men received intravenous infusions of either aminophylline (6 mg/kg, N = 3) or theophylline (5 mg/kg, N = 5) over 1 hour followed by either 5 Gm standard activated charcoal every 2 hours, 20 Gm every 2 hours, or 5 Gm PX-21 activated charcoal (with 3.6 times the surface area) every 2 hours. Theophylline t 1/2 and AUC with each regimen were respectively 6.3 +/- 0.5 (S.E.) hours and 88.9 +/- 8.4 mg/liter X hr with 5 Gm standard activated charcoal, 5.3 +/- 0.3 hours and 75.4 +/- 4.9 mg/liter X hr with 5 Gm PX-21, and 4.9 +/- 0.2 hours and 67.7 +/- 3.6 mg/liter X hr with 20 Gm standard activated charcoal. There was a relationship between the activated charcoal surface area and the reduction in theophylline t 1/2 and AUC. We conclude that the clearance of theophylline is related to the surface area of activated charcoal administered and that PX-21 may be a more potent activated charcoal product for enhancing theophylline removal.