Cidnavir 75mg (Cidofovir Vials) 75mg/ml

Cidofovir has a single licensed indication, and its safety in other settings has not been established.

• Cytomegalovirus retinitis in AIDS: the only licensed indication, treating this sight-threatening infection in patients with advanced HIV.
• Second-line therapy: generally used when ganciclovir or foscarnet have failed, are not tolerated, or are unsuitable.
• Not established for other CMV disease: safety and efficacy are not established for CMV pneumonitis, gastroenteritis, congenital or neonatal CMV, or CMV in people without HIV.
• Not a cure: it controls the infection rather than eliminating it, and retinitis can still progress during and after treatment.
• Intravenous infusion only: it must never be given by intraocular injection or by any route other than dilute intravenous infusion.

• Cidofovir is an acyclic nucleoside phosphonate. Once inside the cell, host enzymes convert it into its active diphosphate form, which resembles a natural DNA building block. The viral enzyme that copies cytomegalovirus DNA incorporates it by mistake, and this halts the growing DNA chain and suppresses viral replication. Because the drug does not need a viral enzyme for its initial activation, it stays active against some strains resistant to other antivirals.

Kidney damage is the main dose-limiting toxicity and can be severe after very few doses; renal monitoring before every dose is mandatory.

Common Side Effects

• Impaired kidney function and protein in the urine: very common and the reason renal tests precede every dose.
• Nausea, vomiting, and fever: frequent during and after infusion.
• Neutropenia: falls in white cell counts requiring monitoring before each dose.
• Hair loss and rash: reported during treatment courses.

Serious or Rare Side Effects

• Acute renal failure: has occurred after as few as one or two doses, sometimes requiring dialysis or contributing to death.
• Uveitis, iritis, or low eye pressure: inflammation inside the eye and ocular hypotony; report eye pain or vision change promptly.
• Metabolic acidosis and Fanconi syndrome: kidney tubule damage causing electrolyte disturbance; monitor blood chemistry throughout.

Cidofovir carries boxed warnings for nephrotoxicity, neutropenia, and carcinogenic and teratogenic effects, so protocol adherence is not optional.

• Give probenecid and saline prehydration with every dose: oral probenecid before and after, plus intravenous normal saline immediately before, are mandatory.
• Check renal function within 48 hours of each dose: measure serum creatinine and urine protein, and modify or withhold the dose for any change.
• Do not use with other nephrotoxic agents: this is a contraindication, and such agents must be stopped in advance where possible.
• Exclude patients with existing renal impairment: it is contraindicated where serum creatinine is above 1.5 mg/dL, creatinine clearance is 55 ml/min or less, or urine protein reaches 2+.
• Monitor neutrophil counts and eye health: check white cells before each dose and watch for signs of uveitis or iritis.
• Never exceed the recommended dose, frequency, or infusion rate, and never give it by intraocular injection.

Interactions matter more than usual here, because both cidofovir and the mandatory probenecid have significant effects.

Major Interactions (Avoid)

• Other nephrotoxic agents (aminoglycosides, amphotericin B, foscarnet, intravenous pentamidine, vancomycin, NSAIDs): contraindicated, and these should be stopped at least seven days before treatment.
• Tenofovir and other agents cleared by the same kidney pathway: combined renal handling raises the risk of tubular injury.

Moderate Interactions (Monitor Closely)

• Zidovudine: because of probenecid, the zidovudine dose should be held or halved on days when cidofovir is given.
• Drugs cleared by renal tubular secretion: probenecid alters the handling of many medicines, so review the whole list.
• Sulfa-containing medicines: relevant because severe probenecid or sulfa hypersensitivity is a contraindication to the regimen.