Dose dependent pharmacokinetics of albendazole in human

Pharmacokinetics of albendazole sulphoxide (ABZ-SO) in three different single oral doses of albendazole (ABZ) (400, 800 and 1200 mg) was studied in 10 healthy human volunteers in a double blind three-way crossover design. The serum levels of albendazole main metabolite, albendazole sulphoxide (ABZ-SO), were analysed by a modified high-pressure liquid chromatography method. (ABZ is not detectable in biological fluids itself.)For ABZ-SO, there was no significant difference in the biological half life, normalized serum peak concentration (C(max-ABZ-SO)/Dose(ABZ)), time to reach peak concentration (T(max)) and mean residence time (MRT), whereas apparent clearance (Cl(p)/F), apparent distribution volume (V(d)/F), normalized area under the serum concentration-time curve (AUC(ABZ-SO)/Dose(ABZ)) and normalized area under the first moment curve (AUMC(ABZ-SO)/Dose(ABZ)) of albendazole main metabolite (ABZ-SO) were statistically different at different doses of the parent drug, resulting in substantially lower serum concentration and thereafter AUC(ABZ-SO)/Dose(ABZ) and AUMC(ABZ-SO)/Dose(ABZ) in higher doses. These observations indicate dose dependent pharmacokinetics of albendazole (observed for ABZ-SO), which were explained on the basis of a change in fraction of dose absorbed (F) as a result of slow and incomplete dissolution of the main drug in the GI tract.