Final answer:
Acyclovir, valacyclovir, and famciclovir are antiviral drugs that inhibit viral DNA replication. They have different mechanisms of action and can be used to treat various herpes virus infections. Resistance to these drugs can occur, and they can have side effects such as headache, nausea, and kidney damage.
Step-by-step explanation:
Acyclovir, valacyclovir, and famciclovir are antiviral drugs commonly used to treat viral infections caused by herpes viruses. Their mechanism of action (MOA) involves inhibiting viral DNA replication by acting as nucleoside analogs.
Acyclovir is a guanosine analog, and it is activated by the viral enzyme thymidine kinase, which leads to chain termination during DNA replication. Valacyclovir and famciclovir are prodrugs that are bioactivated to acyclovir and penciclovir, respectively. Both valacyclovir and famciclovir have enhanced oral bioavailability compared to acyclovir, making them more effective.
Resistance to these drugs can occur due to mutations in the viral genes that encode the enzymes involved in their activation. Additionally, prolonged and frequent use of these drugs can lead to the development of drug-resistant strains of the virus.
Common adverse effects (AE) of acyclovir, valacyclovir, and famciclovir include headache, nausea, vomiting, diarrhea, and rash. Serious adverse effects are rare but can include kidney damage and neurological symptoms.