Cidofovir

What is Cidofovir?
Cidofovir is an intravenous antiviral medication, a nucleotide analog that selectively inhibits viral DNA polymerase. It’s primarily used to treat cytomegalovirus (CMV) retinitis in patients with AIDS; though not curative, it helps slow disease progression.

Approved & Off‑Label Uses

FDA-approved: CMV retinitis in HIV/AIDS patients.

Off-label (limited or investigational):

Acyclovir-resistant herpes simplex or varicella-zoster infections

Adenovirus infections, particularly in immunocompromised individuals (e.g., post-transplant)

Monkeypox under CDC protocols

Topical use for warts, papillomatosis, Kaposi sarcoma, and molluscum contagiosum.

Mechanism of Action

Activated intracellularly to cidofovir diphosphate.

This metabolite inhibits viral DNA polymerase and incorporates into viral DNA, halting replication.

Selectivity for viral vs human polymerase ranges from 8- to 600-fold.

Dosage & Administration

Route: Intravenous infusion only.

Co-therapies: Administered with probenecid and IV saline prehydration to reduce the risk of nephrotoxicity. 

Schedule: Typically weekly induction followed by maintenance every 2 weeks, guided by protocols and renal function.

Safety & Precautions
Nephrotoxicity & Renal Effects

Primary toxicity: Acute kidney injury is seen even after 1–2 doses.

Protective measures: Mandatory hydration and probenecid; monitor SCr, proteinuria, neutrophils before each dose.

Contraindications: Pre-existing renal impairment (CrCl ≤ 55 mL/min, proteinuria ≥ 100 mg/dL) or concurrent nephrotoxic medications.

Other Adverse Effects

Common: nausea, vomiting, neutropenia, headache, hair loss.

May provoke uveitis, iritis, ocular hypotony—periodic eye exams recommended

Rare but serious: Fanconi syndrome, metabolic acidosis, hypersensitivity reactions.

Carcinogenic and teratogenic in animals—avoid use during pregnancy; fertility impact possible.

Clinical Monitoring

Renal: Before each dose and regularly during treatment—adjust or discontinue if worsening renal function.

Hematologic: Monitor CBC for neutropenia.

Eye health: Ophthalmologic exams to catch uveitis or vision changes early.

Electrolytes: Watch serum calcium, phosphate, and bicarbonate for proximal tubular dysfunction.