A rare case of acyclovir-induced thrombocytopenia.

Acyclovir is used for its potent antiviral properties for the mucocutaneous herpes, herpes zoster, herpes encephalitis, and genital herpes simplex. The drug has a very wide distribution involving almost every organ of the body, with excretion into the urine. Urine analysis, kidney function, liver function, and complete blood counts are some of the monitoring parameters. The active triphosphate form of the drug inhibits DNA synthesis and viral replication by competing with deoxyguanosine triphosphate for viral DNA polymerase and being incorporated into viral DNA. Because the drug is only absorbed by the cells that are virus infected, acyclovir has minimal side effects at therapeutic doses. However, at high intravenous infusions, severe central nervous system (malaise), gastrointestinal (nausea/vomiting), renal (elevated blood urea nitrogen/creatinine), hepatic (elevated liver enzymes), and skin dyscrasias have been found to occur. There have been few case reports of bone marrow suppression and only one case report so far of acyclovir-related isolated thrombocytopenia. Whether there is any further association between acyclovir and thrombotic thrombocytopenic purpura/hemolytic uremic syndrome is the next dilemma if such an association is established. Here, the authors present a case report of a 58-year-old man with acquired immune deficiency syndrome on highly active antiretroviral therapy who went into severe thrombocytopenia on starting acyclovir.