The adverse reactions listed below have been observed in controlled and uncontrolled clinical trials in approximately 700 patients who received ZOVIRAX at ~5 mg/kg (250 mg/m²) 3 times daily, and approximately 300 patients who received ~10 mg/kg (500 mg/m²) 3 times daily.

The most frequent adverse reactions reported during administration of ZOVIRAX were inflammation or phlebitis at the injection site in approximately 9% of the patients, and transient elevations of serum creatinine or BUN in 5% to 10% (the higher incidence occurred usually following rapid [less than 10 minutes] intravenous infusion). Nausea and/or vomiting occurred in approximately 7% of the patients (the majority occurring in nonhospitalized patients who received 10 mg/kg). Itching, rash, or hives occurred in approximately 2% of patients. Elevation of transaminases occurred in 1% to 2% of patients.

The following hematologic abnormalities occurred at a frequency of less than 1%: anemia, neutropenia, thrombocytopenia, thrombocytosis, leukocytosis, and neutrophilia. In addition, anorexia and hematuria were observed.

Observed During Clinical Practice

In addition to adverse events reported from clinical trials, the following events have been identified during post-approval use of ZOVIRAX for Injection in clinical practice. 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 ZOVIRAX, or a combination of these factors.

General

Anaphylaxis, angioedema, fatigue, fever, headache, pain, peripheral edema.

Digestive

Abdominal pain, diarrhea, gastrointestinal distress, nausea.

Cardiovascular

Hypotension.

Hematologic and Lymphatic

Disseminated intravascular coagulation, hemolysis, leukocytoclastic vasculitis, leukopenia, lymphadenopathy.

Hepatobiliary Tract and Pancreas

Elevated liver function tests, hepatitis, hyperbilirubinemia, jaundice.

Musculoskeletal

Myalgia.

Nervous

Aggressive behavior, agitation, ataxia, coma, confusion, delirium, dizziness, dysarthria, encephalopathy, hallucinations, obtundation, paresthesia, psychosis, seizure, somnolence, tremor. These symptoms may be marked, particularly in older adults (see PRECAUTIONS).

Skin

Alopecia, erythema multiforme, photosensitive rash, pruritus, rash, Stevens-Johnson syndrome, toxic epidermal necrolysis, urticaria. Severe local inflammatory reactions, including tissue necrosis, have occurred following infusion of ZOVIRAX into extravascular tissues.

Special Senses

Visual abnormalities.

Urogenital

Renal failure, elevated blood urea nitrogen, elevated creatinine (see WARNINGS).

Read the Zovirax Injection (acyclovir for injection) Side Effects Center for a complete guide to possible side effects »

See CLINICAL PHARMACOLOGY: Pharmacokinetics.

Last reviewed on RxList: 9/7/2007
This monograph has been modified to include the generic and brand name in many instances.