Bioavailability of levamisole administered by subcutaneous and oral routes in rabbits

The bioavailability of levamisole in rabbits was determined after subcutaneous and oral administration at three dose levels of 12.5, 16.0 and 20.0 mg/kg. After non-compartmental analysis the mean values obtained were: Cmax = 3.54, 4.51 and 5.39 micrograms/ml; tmax = 12.0, 22.0 and 20.0 min; F = 134.8, 105.4 and 124.1% after subcutaneous administration for each dose, respectively, and Cmax = 0.71, 1.32 and 1.77 micrograms/ml; tmax = 46.0, 96.0 and 84.0 min; F = 53.0, 62.0 and 80.7% after oral administration. The extent and rate of absorption from the two routes differed significantly, except for tmax at the 12.5 mg/kg dose. After compartmental analysis the pharmacokinetics of levamisole was characteristic of a two-compartment open model in 13 rabbits and of a one-compartment open model in two rabbits after subcutaneous administration, while it was two compartmental in nine and one compartmental in six rabbits after oral administration. The ka values were 0.321, 0.145 and 0.145 min-1 after subcutaneous administration and 0.054, 0.023 and 0.027 min-1 after oral administration. There were no significant differences between the values of Cmax, tmax and AUC calculated by compartmental and non-compartmental analysis.