Bupropion is absorbed rapidly after single-dose oral administration of tablets, capsules, or aqueous solution of the hydrochloride salt. Peak bupropion plasma concentrations are generally attained within 2 hours, followed by a biphasic decline. The half-life of the initial (alpha) phase is approximately 1.5 hours and that of the second (beta) phase is approximately 14.0 hours. An oral dose of bupropion is subjected to extensive first-pass metabolism. The ratio between plasma clearance and fraction absorbed (approximately 2 L/hr/kg) is consistent within the 50-250 mg single dose range.