Activated charcoal alone and followed by whole-bowel irrigation in preventing the absorption of sustained-release drugs

Objective: Our objective was to study the effect of activated charcoal on t he absorption of sustained-release drugs ingested 1 hour earlier and to exa mine whether whole-bowel irrigation affects the efficacy of charcoal. Methods: In this randomized, 3-phase crossover study, 9 healthy subjects re ceived, at the same time, 200 mg carbamazepine, 200 mg theophylline, and 12 0 mg verapamil. All drugs were given as sustained-release tablets. One hour after taking the tablets, the subjects were assigned to one of the followi ng treatments: 25 g activated charcoal as a suspension, 25 g activated char coal as a suspension followed by whole-bowel irrigation with polyethylene g lycol (PEG) electrolyte lavage solution, or 200 mL water (control). The abs orption of the drugs was characterized by using the area under the plasma d rug concentration-time curve from time zero to 24 hours [AUC(0-24)], peak p lasma concentration (C-max), C-max minus the plasma concentration at 1 hour (C-Delta), and time to peak (t(max)). Results: Activated charcoal alone given 1 hour after drug intake significan tly (P < .001) reduced the absorption [AUC(0-24)] of all 3 drugs (by 62%-75 %). Also the C-max and C-Delta values of these drugs were significantly red uced by charcoal alone. Whole-bowel irrigation did not increase significant ly the effect of charcoal on any absorption parameters of the 3 drugs studi ed. On the contrary, whole-bowel irrigation significantly (P < .01) decreas ed the efficacy of charcoal with respect to carbamazepine: Conclusions: Activated charcoal alone given 1 hour after intake of sustaine d-release drugs was effective in preventing the absorption of all 3 drugs s tudied. Whole-bowel irrigation may even decrease the efficacy of charcoal i f the drug is well adsorbable onto charcoal. However, our study was perform ed with therapeutic drug doses only. In overdoses their possible effects on gastrointestinal motility may modify the efficacy of decontamination metho ds.