|Systematic (IUPAC) name|
|IV, oral, intravitreal|
|Metabolism||guanylate kinase (CMV UL97 gene product)|
|(what is this?)|
Ganciclovir (INN) // or DHPG (9-(1,3-dihydroxy-2-propoxymethyl)guanine, alternative spelling: "Gancyclovir") is an antiviral medication used to treat cytomegalovirus (CMV) infections. Ganciclovir sodium is marketed under the trade names Cytovene and Cymevene (Roche). Ganciclovir for ocular use is marketed under the trade name Vitrasert (Bausch & Lomb). A prodrug form with improved oral bioavailability (valganciclovir) has also been developed.
Mechanism of action
Ganciclovir is a synthetic analogue of 2′-deoxy-guanosine. It is first phosphorylated to ganciclovir monophosphate by a viral kinase encoded by the cytomegalovirus (CMV) gene UL97 during infection. Subsequently, cellular kinases catalyze the formation of ganciclovir diphosphate and ganciclovir triphosphate, which is present in 10-fold greater concentrations in CMV or herpes simplex virus (HSV)-infected cells than uninfected cells.
Ganciclovir triphosphate is a competitive inhibitor of deoxyguanosine triphosphate (dGTP) incorporation into DNA and preferentially inhibits viral DNA polymerases more than cellular DNA polymerases. In addition, ganciclovir triphosphate serves as a poor substrate for chain elongation, thereby disrupting viral DNA synthesis by a second route.
Ganciclovir is indicated for:
- Sight-threatening CMV retinitis in severely immunocompromised people
- CMV pneumonitis in bone marrow transplant recipients
- Prevention of CMV disease in bone marrow and solid organ transplant recipients
- Confirmed CMV retinitis in people with AIDS (intravitreal implant)
It is also used for acute CMV colitis in HIV/AIDS and CMV pneumonitis in immunosuppressed patients.
Ganciclovir is commonly associated with a range of serious haematological adverse effects. Common adverse drug reactions (≥1% of patients) include: granulocytopenia, neutropenia, anaemia, thrombocytopenia, fever, nausea, vomiting, dyspepsia, diarrhea, abdominal pain, flatulence, anorexia, raised liver enzymes, headache, confusion, hallucination, seizures, pain and phlebitis at injection site (due to high pH), sweating, rash, itch, increased serum creatinine and blood urea concentrations.
Ganciclovir is considered a potential human carcinogen, teratogen, and mutagen. It is also considered likely to cause inhibition of spermatogenesis. Thus, it is used judiciously and handled as a cytotoxic drug in the clinical setting.
Absorption of the oral form is very limited—about 5% fasting, about 8% with food. It achieves a concentration in the central nervous system of about 50% of the plasma level. About 90% of plasma ganciclovir is eliminated unchanged in the urine, with a half-life of 2–6 hours, depending on renal function (elimination takes over 24 hours in end-stage renal disease).
Acute infections are treated in two phases:
- induction phase, 5 mg per kilogram intravenously every 12 hours for 14–21 days, the intravenous dose given as a 1 hour infusion
- maintenance phase, 5 mg per kg intravenously every day
Stable disease is treated with 1000 mg orally three times daily. Similar dosing is used to prevent disease in high-risk patients, such as those infected with human immunodeficiency virus (HIV) or those with organ transplants.
A topical ophthalmic gel preparation of ganciclovir was recently approved for the treatment of acute herpes simplex keratitis.
- Rossi S, editor. Australian Medicines Handbook 2006. Adelaide: Australian Medicines Handbook; 2006. ISBN 0-9757919-2-3
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