Mechanism of action	Cidofovir is an acyclic nucleoside phosphonate analogue that has been shown to have excellent activity against HHV-6 in vitro.
Standard dosage	Induction therapy is 5 mg/kg via IV infusion given over 1 h once a week for 2 consecutive weeks; give saline hydration and probenecid (2 g orally 3 h before dose and 1 g orally at 2 h and 8 h after dose; total 4 g) before and after each infusion. Maintenance therapy is 5 mg/kg via IV infusion given over 1 h every other week with saline hydration and probenecid.
Contraindications	Hypersensitivity to cidofovir, probenecid, or sulfa-containing medications, serum creatinine greater than 1.5 mg/dL, creatinine clearance <55 mL/min, or a urine protein of 9100 mg/dL (equivalent to 92+ proteinuria), concomitant nephrotoxic agents.
Main drug interactions	Nephrotoxicity may affect any renally excreted drugs.
Main side effects	Nephrotoxicity (88 %), anemia (24 %), neutropenia (43 %), fever (58 %), alopecia (27 %), and rash (30 %).
Special points	It is considered second-line therapy against HHV-6 due to nephrotoxicity. A mutation in the U38 gene encoding DNA polymerase can cause resistance to cidofovir