Inhibition of Methadone and Phenobarbital Percutaneous Absorption by Parenterally Administered Ethanol

Four hours after the topical administration of either aqueous methadone hydrochloride or sodium phenobarbital to hairless (SKH, hr-1/hr-1) mice, the mean drug concentration in liver was significantly lower in ethanol-treated mice than in control animals that had received only water (methadone study, p < 0.01; phenobarbital study, p < 0.02). No statistically significant difference was noted between the mean concentrations for test and control mice when either methadone or phenobarbital were given by intraperitoneal injection instead of topically, suggesting that ethanol inhibits the percutaneous absorption of these drugs in vivo.