Acyclovir

WARNINGS Acyclovir tablets are intended for oral ingestion only. Renal failure, in some cases resulting in death, has been observed with acyclovir therapy (see ADVERSE REACTIONS: Observed During Clinical Practice and OVERDOSAGE ). Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), which has resulted in death, has occurred in immunocompromised patients receiving acyclovir therapy. Severe cutaneous adverse reactions (SCARs), including acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and erythema multiforme (EM) have been reported with acyclovir (see CONTRAINDICATIONS and ADVERSE REACTIONS ). Discontinue acyclovir tablets immediately if a painful rash with mucosal involvement or a progressive severe rash develops. Closely monitor clinical status and initiate appropriate therapy. Acyclovir tablets are contraindicated in patients who have developed SCARs with the use of acyclovir or valacyclovir, or any component of the formulation (see CONTRAINDICATIONS and ADVERSE REACTIONS ).

ADVERSE REACTIONS Herpes Simplex: Short-Term Administration: The most frequent adverse events reported during clinical trials of treatment of genital herpes with acyclovir tablets 200 mg administered orally 5 times daily every 4 hours for 10 days were nausea and/or vomiting in 8 of 298 patient treatments (2.7%). Nausea and/or vomiting occurred in 2 of 287 (0.7%) patients who received placebo. Long-Term Administration: The most frequent adverse events reported in a clinical trial for the prevention of recurrences with continuous administration of 400 mg (two 200 mg capsules) 2 times daily for 1 year in 586 patients treated with acyclovir tablets were nausea (4.8%) and diarrhea (2.4%). The 589 control patients receiving intermittent treatment of recurrences with acyclovir tablets for 1 year reported diarrhea (2.7%), nausea (2.4%), and headache (2.2%). Herpes Zoster: The most frequent adverse event reported during 3 clinical trials of treatment of herpes zoster (shingles) with 800 mg of oral acyclovir tablets 5 times daily for 7 to 10 days in 323 patients was malaise (11.5%). The 323 placebo recipients reported malaise (11.1%). Chickenpox: The most frequent adverse event reported during 3 clinical trials of treatment of chickenpox with oral acyclovir tablets at doses of 10 to 20 mg/kg 4 times daily for 5 to 7 days or 800 mg 4 times daily for 5 days in 495 patients was diarrhea (3.2%). The 498 patients receiving placebo reported diarrhea (2.2%). Observed During Clinical Practice: In addition to adverse events reported from clinical trials, the following events have been identified during post-approval use of acyclovir tablets. Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to either their seriousness, frequency of reporting, potential causal connection to acyclovir tablets or a combination of these factors. General: Anaphylaxis, angioedema, fever, headache, pain, peripheral edema. Nervous: Aggressive behavior, agitation, ataxia, coma, confusion, decreased consciousness, delirium, dizziness, dysarthria, encephalopathy, hallucinations, paresthesia, psychosis, seizure, somnolence, tremors. These symptoms may be marked, particularly in older adults or in patients with renal impairment (see PRECAUTIONS ). Digestive: Diarrhea, gastrointestinal distress, nausea. Hematologic and Lymphatic: Anemia, leukocytoclastic vasculitis, leukopenia, lymphadenopathy, thrombocytopenia. Hepatobiliary Tract and Pancreas: Elevated liver function tests, hepatitis, hyperbilirubinemia, jaundice. Musculoskeletal: Myalgia. Skin and Subcutaneous Tissue Disorders: Stevens-Johnson Syndrome (SJS), toxic epidermal necrolysis (TEN), acute generalized exanthematous pustulosis (AGEP), and drug reaction with eosinophilia and systemic symptoms (DRESS), erythema multiforme (EM), rashes including photosensitivity, alopecia, pruritus, urticaria (see CONTRAINDICATIONS and WARNINGS ). Special Senses: Visual abnormalities. Urogenital: Renal failure, renal pain (may be associated with renal failure), elevated blood urea nitrogen, elevated creatinine, hematuria (see WARNINGS ).