No clinically significant interactions have been identified.
Acyclovir is eliminated primarily unchanged in the urine via active renal tubular secretion. Any drugs administered concurrently that compete with this mechanism may increase acyclovir plasma concentrations. Probenecid and cimetidine increase the AUC of acyclovir by this mechanism and reduce acyclovir renal clearance. Similarly, increases in plasma AUCs of acyclovir and of the inactive metabolite of mycophenolate mofetil, an immunosuppressant agent used in transplant patients have been shown when the drugs are co-administered. However, no dosage adjustment is necessary because of the wide therapeutic index of acyclovir.
Infusion: In patients receiving Zovirax IV, caution is required during concurrent administration with drugs which compete with acyclovir for elimination, because of the potential for increased plasma levels of one or both drugs or their metabolites. Increases in plasma AUCs of acyclovir and of the inactive metabolite of mycophenolate mofetil, an immunosuppressant agent used in transplant patients, have been shown when the drugs are co-administered. Care is also required (with monitoring for changes in renal function) if administering Zovirax with drugs which affect other aspects of renal physiology (eg, cyclosporin, tacrolimus).