Herpes antivirals (nucleoside analogues)
Herpes antivirals are activated inside infected cells and block the viral DNA polymerase, which stops herpes viruses from copying themselves. Acyclovir, valacyclovir, and famciclovir treat genital herpes, shingles, and chickenpox, and IV acyclovir treats severe infections such as herpes encephalitis. Nausea, diarrhea, and headache are the most common side effects. High doses, especially by IV, can form crystals in the kidneys and cause kidney injury, so staying well hydrated matters and doses are lowered when kidney function is reduced.