Pharmacokinetics of aminolevulinic acid after oral and intravenous administration in dogs

The purpose of these studies was to examine the pharmacokinetics, oral bioa vailability, and systemic side effects of aminolevulinic acid (ALA) in beag le dogs after oral and i.v. administration. Oral and i.v. doses of ALA (128 mg of ALA hydrochloride, equivalent to 100 mg of ALA) were administered to four animals using a crossover design. Animals were allowed a 5-week washo ut period between doses. Plasma ALA concentrations were determined using pr ecolumn fluorescent derivatization and reversed-phase HPLC, Plasma concentr ations after i.v. administration declined rapidly with a terminal half-life of 19.5 +/- 2.5 min (mean +/- S.D.). Total body clearance and volume of di stribution at steady state averaged 6.79 +/- 1.77 ml/min/kg and 259 +/- 128 ml/kg, respectively. Peak plasma concentrations of ALA after oral administ ration ranged from 1.27 to 9.42 mu g/ml. Oral bioavailability in these anim als averaged 41.2 +/- 14.8% (range, 23.5-58.5%). These studies demonstrate that oral administration may provide a convenient and efficient route of de livery of ALA for photodynamic therapy in patients.