Acyclovir Side Effects

Brand Names: Zovirax

Please note - some side effects for Acyclovir may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Acyclovir - for the Consumer

Acyclovir

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Acyclovir:

Changes in vision; dizziness; drowsiness; nausea; sensitivity to sunlight.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); aggressive behavior; agitation; blood in the urine; confusion; dark urine; decreased consciousness; decreased urination; fatigue; fever; hallucinations; lower back pain; pain or redness at the injection site; painful urination; red, swollen, blistered, or peeling skin; seizures; stomach pain; tremors; unusual bleeding or bruising; urination problems; vomiting; yellowing of the eyes or skin.

Acyclovir Capsules

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Acyclovir Capsules:

Diarrhea; general body discomfort; headache; nausea/vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); aggressive behavior; blood in the urine; confusion; decreased consciousness; decreased urination; hallucinations; lower back pain; mental or mood changes; red, swollen, blistered, or peeling skin; seizures; unusual bruising or bleeding.

Acyclovir Cream

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Acyclovir Cream:

Burning or stinging; dry or cracked lips; flakiness or dryness of the skin; itching.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue; excessive itching; dizziness).

Acyclovir Ointment

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Acyclovir Ointment:

Swelling, pain, burning, stinging, or itching at the application site.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue; itching; dizziness).

Acyclovir Suspension

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Acyclovir Suspension:

Diarrhea; dizziness; drowsiness; general body discomfort; headache; muscle weakness; nausea; stomach upset; vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); aggressive behavior; blood in the urine; confusion; decreased consciousness; decreased urination; easy bruising or bleeding; fever; hallucinations; hoarseness; lower back pain; mania; mental or mood changes; red, swollen, or blistered skin; seizures; swelling of the hands or feet; vision changes; yellowing of the eyes or skin.

Acyclovir Side Effects - for the Professional

Acyclovir Tablets

Herpes Simplex

The most frequent adverse events reported during clinical trials of treatment of genital herpes with Acyclovir 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.

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 were nausea (4.8%) and diarrhea (2.4%). The 589 control patients receiving intermittent treatment of recurrences with Acyclovir 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 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 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. 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, or a combination of these factors.

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

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.

Diarrhea, gastrointestinal distress, nausea.

Anemia, leukocytoclastic vasculitis, leukopenia, lymphadenopathy, thrombocytopenia.

Elevated liver function tests, hepatitis, hyperbilirubinemia, jaundice.

Myalgia.

Alopecia, erythema multiforme, photosensitive rash, pruritus, rash, Stevens-Johnson syndrome, toxic epidermal necrolysis, urticaria.

Visual abnormalities.

Renal failure, elevated blood urea nitrogen, elevated creatinine, hematuria.

Side Effects by Body System

Gastrointestinal

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

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

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 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

Local adverse effects associated with intravenous administration of acyclovir 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

Cardiovascular side effects have included hypotension.

Dermatologic

Dermatologic side effects have included alopecia, erythema multiforme, hives, photosensitive rash, pruritus, rash, Stevens-Johnson syndrome, toxic epidermal necrolysis, and urticaria.

Hematologic

Hematologic and lymphatic side effects have included anemia, disseminated intravascular coagulation, hemolysis, leukocytoclastic vasculitis, leukocytosis, leukopenia, lymphadenopathy, neutropenia, neutrophilia, thrombocytosis, thrombocytopenia, and pancytopenia.

Hepatic

Hepatic side effects have included elevated liver function tests, hepatitis, hyperbilirubinemia, and jaundice.

Hypersensitivity

Hypersensitivity reactions have included anaphylaxis.

Ocular

Ocular side effects have included visual abnormalities.

Musculoskeletal

Musculoskeletal side effects reported have included myalgia and dysarthria.

Other

Other side effects have included angioedema, fever, malaise, pain, fatigue, peripheral edema, and increased lactate dehydrogenase.

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