Effects of activated charcoal and sorbitol on sodium pentobarbital absorption in the rat

Three activated charcoals were tested for their ability to reduce the oral absorption of sodium pentobarbital (SP) in rats. Fasted adult, male rats were given 40 mg/kg of C-14 labelled SP by gavage (2 ml). Five minutes after drug administration, the animals were given 40 mg of either Darco (G-60), United States Pharmacopeia (USP) or SuperChar (SC) activated charcoals. The charcoals were administered as a slurry in either 1 ml of water, or 1 ml of 70 percent (w/v) sorbitol solution. Water (control) and sorbitol given alone were tested separately. Various pharmacokinetic parameters were calculated from the plasma concentration of SP determined at various time intervals after drug administration. When given in water, only SC significantly (p less than .01) reduced the peak plasma concentration and oral bioavailability of SP. Sorbitol given alone produced diarrhea but did not affect drug absorption. However, sorbitol selectively enhanced the effectiveness of G-60 and USP charcoals and, as a result, all charcoals significantly reduced SP absorption when given along with the cathartic. The results suggest that when given in water, charcoal antidotal effectiveness is proportional to absorptive surface area, and that sorbitol may enhance the antidotal effectiveness of some charcoals but not others.