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The bioavailability of L-dopa following rectal administration of a series of short-chain alkyl esters of L-dopa was determined in rats and dogs. The esters were stable (>360 min) to hydrolysis in physiological buffer. In vitro enzymatic hydrolysis of the esters in plasma was species dependent, with the hydrolytic rate being faster in rat plasma (t1/2 600 mg/ml) esters of L-dopa are potential candidates for controlled-release rectal delivery systems designed to provide more constant plasma L-dopa levels.