Pharmacology · Anti-herpesvirus agents
Cidofovir !
An intravenous antiviral for CMV retinitis in AIDS. It works without the viral kinase but is very toxic to the kidneys.
Updated 2026-11-01
The figure shows cidofovir diphosphate, its active form, in the DNA polymerase of mpox virus, a poxvirus that cidofovir also inhibits; no human CMV polymerase structure with cidofovir is available.
Mechanism of action
Cidofovir is a cytidine nucleotide analogue (a phosphonate). Cellular kinases, not viral ones, convert it to cidofovir diphosphate, which competes with dCTP and is used by the viral DNA polymerase, slowing and finally stopping chain elongation. Because it does not need viral activation, it still inhibits thymidine kinase-deficient herpes simplex and UL97-mutant CMV.
- Enters cells already carrying one phosphonate group
- Cellular kinases make cidofovir diphosphate
- The diphosphate competes with dCTP at the viral DNA polymerase
- Viral DNA elongation slows and stops
Pharmacokinetics
- Absorption
- Intravenous only
- Elimination
- By the kidneys; probenecid reduces its tubular secretion
Indications
- CMV retinitis in people with AIDS Cytomegalovirus infection →
Adverse effects
Common
- Proteinuria and rising creatinine
- Neutropenia
- Fever, nausea and vomiting (partly from probenecid)
- Low intraocular pressure
Contraindications
- Impaired kidney function (creatinine or proteinuria above label limits)
- Other nephrotoxic drugs at the same time or within the previous 7 days
- Severe hypersensitivity to probenecid or other sulfa-containing drugs
- Direct injection into the eye
Key interactions
- Other nephrotoxic drugs, now or in the previous 7 days
- Contraindicated: much higher risk of kidney injury
- Probenecid
- Required with each dose to protect the kidney; it also changes the clearance of other drugs such as zidovudine
What is monitored
- Serum creatinine and urine protein before every dose
- Neutrophil count
- Intraocular pressure and visual acuity
- Signs of metabolic acidosis
Administration and safety
- Intravenous saline prehydration and oral probenecid with every dose
- Prepared with protective equipment in a biological safety cabinet; disposed of as a cytotoxic drug
- Never injected into the eye
Nursing care
- Confirm creatinine and urine protein results before each infusion
- Give the saline and probenecid as scheduled
- Ask about eye pain, redness or blurred vision
- Watch for fever, rash or nausea from probenecid
Pregnancy and breastfeeding
Embryotoxic in animals; used only if the benefit justifies the risk to the fetus.
Test yourself
Think of the answer, then tap the question to see it.
Why is cidofovir active against thymidine kinase-deficient herpes viruses?
It is a phosphonate activated by cellular kinases, so it does not need the viral kinase.
What two measures protect the kidney with every dose of cidofovir?
Intravenous saline prehydration and oral probenecid.
Which tests are checked before every dose of cidofovir?
Serum creatinine and urine protein (plus the neutrophil count).
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - CIDOFOVIR injection, solution (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 62 (McGraw Hill, 2023).
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Representative model, for educational purposes only.