Inhibits viral DNA synthesis by competitive inhibition of the viral DNA polymerase and incorporation into the nascent viral DNA chain which leads to chain termination.
Ganciclovir
Ganciclovir is much more toxic than other drugs in this class. Adequate hydration is needed when using these drugs due to potential toxicity to veins.
Ganciclovir adverse effects include:
- GI upset
- Neutropenia (particularly when given with anti-virals for HIV)
- Neurological effects such as headache, confusion, hallucinations and seizures
Due to teratogenicity, men treated with ganciclovir should use barrier contraception during treatment and for a further 3 months.
Aciclovir
Few adverse effects are seen, but include:
- GI upset
- Rash
- Headache
- Rarely, hepatotoxicity, blood disorders and CNS toxicity
Patients should be warned about the symptoms of neutropenia and thrombocytopenia. If these occur, they should seek medical help.
Aciclovir - only 20% of the oral dose is absorbed and peak plasma concentrations are reached in 1-2 hours. The drug is widely distributed, reaching concentrations in the CSF that are 50% of those in the plasma. It is excreted by the kidneys, partly by glomerular filtration and partly by tubular secretion.
Ganciclovir - after intravenous administration it has a half life of four hours and is excreted by the kidneys.
