Study Objectives: To determine the relative effect of a new charcoal cookie formulation on the absorption of orally administered cimetidine compared to a standard aqueous charcoal product; to compare the relative palatability of the two products. Design: Prospective, open-label, three-way cross-over trial Setting: General Clinical Research Center at University of Maryland Medical Center Patients: 8 healthy volunteers (ages 18 to 35 years of age). Intervention: After an overnight fast, subjects ingested cimetidine 800 mg tablet. At 15 minutes after the cimetidine dose subjects ingested either water, 3 charcoal cookies (equivalent to 7.2 g charcoal) or 7.2 g of aqueous activated charcoal suspension. Measurements: Venous blood samples were obtained over an 8 hour period for noncompartmental pharmacokinetic analysis including AUC and Cmax. Subjects evaluated the palatability of each product using a visual analog scale (VAS). Main Results: Both charcoal products effectively adsorbed cimetidine resulting in decreased absorption of most of the cimetidine dose. There was no difference in median percent decrease in cimetidine AUC (mg*hr/L) for the charcoal suspension and charcoal cookie [91.8% vs 82.1%] (p=0.505]. Similarly, there was no difference in the median percent decrease in Cmax (mg/L) for the charcoal suspension and charcoal cookies [82.6% vs 64.0%] (p=0.574). The palatability taste scores on VAS were 2.32 ±0.83 for the charcoal cookie and 1.08 ± 0.70 for the charcoal suspension. There was a significant difference in the palatability scores (p=0.001). All products were well tolerated and there were no adverse events reported. Conclusions: A new charcoal cookie formulation is as effective as the aqueous charcoal suspension at reducing absorption of cimetidine. The charcoal cookie is more palatable than the aqueous charcoal suspension.