In a sequential pharmacokinetic study, healthy male volunteers (n=8) were administered a single oral dose of 400 mg albendazole, in absence and after short-term (2 doses) and long-term (8 days) treatment with ritonavir 200 mg twice daily. Pharmacokinetic parameters of albendazole and  its metabolite albendazole sulfoxide, were not changed by short-term administration of ritonavir. However long-term administration resulted in significant changes in albendazole disposition, with a significant decrease in albendazole and albendazole sulfoxide AUC0-24 (73% and 59% respectively) and Cmax (74% and 48% respectively). Tmax and the terminal half-life were not significantly changed. The observation is most likely due to a ritonavir-mediated induction of metabolising enzymes (CYP2C9, CYP1A2, UGTs) or transporters, although changes in absorption are also possible. These findings need to be replicated with a key boosted PI such as lopinavir/ritonavir. 
Effect of ritonavir on the pharmacokinetics of the benzimidazoles albendazole and mebendazole: an interaction study in healthy volunteers. Corti N, Heck A, Rentsch K, et al.Eur J Clin Pharmacol. 2009;65:999-1006.