Decreased absorption of propoxyphene by activated charcoal

In 1968 we first suggested that activated charcoal (AC) should be administered in the emergency treatment of propoxyphene overdosage. The dramatic increase in recent years of deaths involving propoxyphene has prompted us to again evaluate the efficacy of AC in preventing absorption of propoxyphene from the GI tract. Male rats (100-125 g) were administered propoxyphene hydrochloride (P-HCl, 350 mg/kg) or propoxyphene napsylate (P-N, 825 mg/kg) either dissolved or suspended in 5% acacia in H2O. After 30 min the rats were administered either AC at 10 times the drug dose or water. Surviving rats were sacrificed at 1, 2, 4, 8, 12, and 24 h; the brain, liver, and both kidneys were removed intact, weighed, and stored at -70 degrees C. After lyophilization, the tissues were analyzed for propoxyphene and its metabolite, norpropoxyphene, by GLC. There were significantly less deaths in rats that received P-HCl + AC or P-N + AC than rats that received either P-HCl or P-N alone (9 vs 19, p less than .01 and 5 vs 10, p less than .05 respectively). Tissue levels of propoxyphene and norpropoxyphene were similarly significantly reduced. These studies provide further evidence of the efficacy of AC in propoxyphene overdosage.