Clinical use and toxicity

Oral acyclovir is commonly used for the treatment of mucocutaneous and genital herpes lesions and for prophylaxis in AIDS and in other immunocompromised patients (eg, those undergoing organ transplantation). The oral drug is well tolerated but may cause (GI) distress and headache. Intravenous administration is used for severe herpes disease, including encephalitis, and for neonatal HSV infection. Toxic effects with parenteral administration include delirium, tremor, seizures, hypotension, and nephrotoxicity.It is given intravenous (IV), oral, or topical route. [Note: The efficacy of topical applications is doubtful.] The drug distributes (CSF). Acyclovir is partially metabolized to an inactive product. Excretion into the urine occurs both by glomerular filtration and by tubular secretion Acyclovir accumulates in patients with renal failure. local irritation may occur from topical application; headache, diarrhea, nausea, and vomiting may result after oral administration. Transient renal dysfunction may occur at high doses or in a dehydrated patient receiving the drug Altered or deficient thymidine kinase and DNA polymerases have been found in some resistant viral strains and are most commonly isolated from immunocompromised patients.Cross-resistance to the other agents in this family occurs. [Note: Cytomegalovirus (CMV) is resistant, because it lacks a specific viral thymidine kinase.]