Increased AUC w/ HIV PIs eg, saquinavir, ritonavir. Enhanced effect of hypotensive drugs, β-blockers eg, propanolol & fentanyl. Enhanced effect w/ cimetidine & muscle relaxants eg, pancuronium Br, vecuronium Br, etc. Decreased renal clearance w/ digoxin. Elevated blood conc w/ immunosuppressants eg, cyclosporin, tacrolimus hydrate. Weakened effects by phenytoin & rifampicin.