Zovirax Side Effects
Generic name: acyclovir
Note: This document contains side effect information about acyclovir. Some of the dosage forms listed on this page may not apply to the brand name Zovirax.
Some side effects of Zovirax may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.
For the Consumer
Applies to acyclovir: capsule, powder for solution, solution, suspension, tablet
Along with its needed effects, acyclovir (the active ingredient contained in Zovirax) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking acyclovir:More common - For acyclovir injection only
- Pain, swelling, or redness at place of injection
- Abdominal or stomach pain
- decreased frequency of urination or amount of urine
- increased thirst
- loss of appetite
- nausea or vomiting
- unusual tiredness or weakness
- Black, tarry stools
- blood in urine or stools
- chills, fever, or sore throat
- convulsions (seizures)
- hallucinations (seeing, hearing, or feeling things that are not there)
- pinpoint red spots on skin
- unusual bleeding or bruising
- Bleeding or oozing from puncture sites or mucous membranes (bowel, mouth, nose, or urinary bladder), continuing
- blistering, peeling, or loosening of skin
- bluish coloring, especially of the hands and feet
- blurred vision
- bruising at the place of injection
- changes in facial skin color
- changes in vision
- decreased consciousness
- difficulty in breathing or swallowing
- dizziness or feeling faint, severe
- fast heartbeat
- itching or skin rash
- large hive-like swelling on face, eyelids, lips, tongue, throat, hands, legs, feet, sex organs
- mood or mental changes
- muscle cramps, pain, or weakness
- pale skin
- red or irritated eyes
- sense of agitation or uneasiness
- shakiness and unsteady walk
- sores, ulcers, or white spots in mouth or on lips
- swelling of eyelids, face, feet, hands, lower legs or lips
- swollen, painful, or tender lymph nodes (glands) in neck, armpit, or groin
- unsteadiness or other problems with muscle control or coordination
- yellow eyes or skin
Some side effects of acyclovir may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:More common - Especially seen with high doses
- General feeling of discomfort or illness
- Burning, prickling, or tingling sensations
- loss of hair
For Healthcare Professionals
Applies to acyclovir: compounding powder, intravenous powder for injection, intravenous solution, oral capsule, oral suspension, oral tablet
Gastrointestinal side effects have been the most frequently reported side effects, and include nausea, vomiting, abdominal pain, and diarrhea.
Nausea and vomiting have been reported with oral and intravenous administration, and have preceded neurotoxicity and nephrotoxicity. Gagging and anorexia have also been reported.
Renal side effects have included renal failure, renal pain (may be associated with renal failure), elevated blood urea nitrogen, elevated serum creatinine, and hematuria. Renal effects generally are transient and resolve over several days following discontinuation of therapy; however fatal renal failure has occurred. Renal damage is most commonly due to crystallization of the drug in the renal tubules. Acute tubular necrosis and interstitial nephritis have also been reported.
Transient renal dysfunction has been reported with both oral and intravenous acyclovir therapy. Crystallization of the drug in renal tubules is thought to be the mechanism for the development of renal dysfunction, based on findings of crystalluria in several case reports and at least one prospective study.
Elderly or renally impaired patients are at greater risk for developing neurotoxicity and further deterioration in renal function.
Nervous system side effects have included aggressive behavior, agitation, ataxia, coma, confusion, decreased consciousness, delirium, delusions, disorientation, dizziness, EEG changes, abnormal cerebrospinal fluid findings, encephalopathy, focal neurological signs, hallucinations, headache, insomnia, irritability, lightheadedness, major depression, mania, myoclonus, obtundation, paresthesia, psychosis, seizure, somnolence, tremors, and Cotard's syndrome. Neurotoxicity generally develops early in acyclovir (the active ingredient contained in Zovirax) treatment and has most commonly been reported in patients with renal failure, the elderly, and in patients following bone marrow transplant. It is thought to be associated with high serum concentrations of acyclovir. Guillain Barre syndrome has been reported in at least one patient receiving acyclovir prophylaxis following allogeneic marrow transplantation.
Acyclovir neurotoxicity is almost exclusively seen in patients with renal failure. These patients may have longstanding chronic renal failure or acute failure associated with acyclovir. Although more commonly seen with intravenous administration of larger doses, neurotoxicity has also been reported in patients receiving oral doses of acyclovir. Following discontinuation of acyclovir, mental status recovers within about a week. Several patients with chronic renal failure exhibiting neurotoxicity improved dramatically following hemodialysis. In one study of renal transplant patients receiving oral acyclovir therapy, one patient developed neurotoxicity, manifested as disorientation, confusion and myoclonus. The symptoms responded to a decrease in dosage. Three other case reports have also described neurologic symptoms, including visual hallucinations, delusions, mania, tremors, myoclonus and EEG changes, which improved following discontinuation of intravenous acyclovir. Rechallenge in one case using a lower dosage resulted in no sequelae.
Local adverse effects associated with intravenous administration of acyclovir (the active ingredient contained in Zovirax) have included inflammation or phlebitis at the injection site. Phlebitis is more common when concentrated solutions (greater than 7 mg/mL) are administered. Skin eruptions have been reported at venipuncture sites and tissue necrosis has occurred after infiltration into extravascular tissues.
Cardiovascular side effects have included hypotension.
Dermatologic side effects have included alopecia, erythema multiforme, hives, photosensitive rash, pruritus, rash, Stevens-Johnson syndrome, toxic epidermal necrolysis, and urticaria.
Hematologic and lymphatic side effects have included anemia, disseminated intravascular coagulation, hemolysis, leukocytoclastic vasculitis, leukocytosis, leukopenia, lymphadenopathy, neutropenia, neutrophilia, thrombocytosis, thrombocytopenia, and pancytopenia.
Hepatic side effects have included elevated liver function tests, hepatitis, hyperbilirubinemia, and jaundice.
Hypersensitivity reactions have included anaphylaxis.
Ocular side effects have included visual abnormalities.
Musculoskeletal side effects reported have included myalgia and dysarthria.
Other side effects have included angioedema, fever, malaise, pain, fatigue, peripheral edema, and increased lactate dehydrogenase.
Genitourinary side effects have included crystalluria.
More Zovirax resources
- Zovirax Monograph (AHFS DI)
- Zovirax Prescribing Information (FDA)
- Zovirax Consumer Overview
- Zovirax Oral, Intravenous Advanced Consumer (Micromedex) - Includes Dosage Information
- Zovirax MedFacts Consumer Leaflet (Wolters Kluwer)
- Acyclovir Professional Patient Advice (Wolters Kluwer)
- acyclovir Buccal mucosa Advanced Consumer (Micromedex) - Includes Dosage Information
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