Antimicrobial Use Guidelines (AMUG) version 21 - UW Health

VALACYCLOVIRUsual DoseAdult: 1 g TID PO OR 500 mg BID PO (UWHC cost/day $5.92-17.76).Indications1. Herpes zoster (shingles) in immunocompetent individuals (1 g TID PO x 7 days). Must be started within 72 hours ofonset of rash to be effective, except in immunocompromised hosts.2. Herpes simplex (genital herpes) – acute recurrence (500 mg BID PO x 3- 5 days).3. Herpes labialis (cold sores) – initiate therapy at first sign of tingling (2 g BID for 1 day).CommentsDose adjustment required for renal impairment. See renal dosing guideline on uconnect.Valacyclovir, a prodrug, is the L-valyl ester of acyclovir. It is metabolized to acyclovir by hepatic enzymes. The oralbioavailability of valacyclovir is 3 to 5 times higher than that of acyclovir, making lower doses and longer dosing intervalspossible. An increasing trend toward mortality from thrombotic thrombocytopenic purpura/hemolytic uremic syndrome(TTP/HUS) was seen in one clinical trial with immunocompromised patients at supranormal doses, making its use in thispopulation questionable. The safety and efficacy of valacyclovir in children have not been established.VALGANCICLOVIRUsual DoseAdult: Induction 900 mg BID PO x 21 days (UWHC cost/day 158.16).Maintenance and prophylaxis 900 mg Q24H PO (UWHC cost/day $79.08).Indications1. Cytomegalovirus (CMV) retinitis, pneumonitis, enterocolitis, esophagitis or bloodstream infections.2. CMV prophylaxis - oral formulation restricted to prophylaxis of CMV infections in transplant recipients receiving a graftfrom a seropositive donor or who are seropositive for CMV and in patients receiving anti-rejection therapy.CommentsDose adjustment required for renal impairment. See renal dosing guideline on uconnect.Oral bioavailability is 60%. Patients should be monitored for progression of CMV retinitis and signs and symptoms ofadverse effects including granulocytopenia, anemia, thrombocytopenia, seizures, sedation, ataxia, confusion, increasedcreatinine, diarrhea, nausea, vomiting, fever, headache, insomnia, peripheral neuropathy, paresthesia and retinaldetachment. Valganciclovir should not be administered if the absolute neutrophil count is less than 500 cells/mcL, theplatelet count is less than 25,000/mcL or the hemoglobin is less than 8 g/dL. The bioavailability of ganciclovir fromvalganciclovir differs significantly from that of ganciclovir capsules; therefore, valganciclovir tablets cannot be substitutedfor ganciclovir capsules on a one-to-one basis. Valganciclovir tablets should not be crushed; may use suspension.Patients taking zidovudine and valganciclovir may not be able to tolerate full doses of both drugs because of themyelosuppressive effects of each drug.Drug InteractionsProbenecid may increase the area under the curve (AUC) of valganciclovir and thus may increase the likelihood of toxicityfrom valganciclovir. Valganciclovir may increase the AUC of didanosine and increase the potential for didanosine toxicity.