Important Safety Information: Acyclovir | Oral Antiviral Tablets

What is this?

This Important Safety Information summarizes key warnings and precautions for Acyclovir Tablets, USP, an oral antiviral medication used for the treatment of herpes zoster (shingles), genital herpes (initial and recurrent episodes), and chickenpox (varicella). Acyclovir works by inhibiting viral DNA replication. Acyclovir Tablets, USP are FDA-approved prescription medications for oral use. This summary does not include all available information. Always read your medication label and follow your healthcare provider’s instructions. 

Most Serious Warnings

Product can cause:

• Renal failure, including cases resulting in death

• Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), particularly in immunocompromised patients

• Severe cutaneous adverse reactions (SCARs), including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), DRESS, AGEP, and erythema multiforme

• Severe allergic reactions, including anaphylaxis and angioedema

• Neurological symptoms such as confusion, hallucinations, agitation, tremors, seizures, or coma, especially in elderly patients or those with renal impairment

Discontinue immediately and seek medical attention if a painful rash with mucosal involvement or progressive severe rash develops. 

Who Should NOT Take Acyclovir

Do not take this medication if you:

• Have had a clinically significant hypersensitivity reaction to acyclovir, valacyclovir, or any component of the formulation

• Have experienced severe cutaneous adverse reactions (SCARs) with acyclovir or valacyclovir

Before Taking Acyclovir, Tell Your Healthcare Provider if You:

• Have kidney disease or reduced renal function

• Are elderly or have age-related kidney changes

• Are taking medications that may affect kidney function

• Are immunocompromised

• Are pregnant, planning to become pregnant, or breastfeeding

• Are taking probenecid or other prescription, over-the-counter, or herbal medications

• Experience frequent recurrences of genital herpes

Dose adjustments are required in patients with renal impairment. Adequate hydration should be maintained during therapy. 

Possible Side Effects

Common (mild to moderate):

• Nausea or vomiting

• Diarrhea

• Malaise

• Headache

Serious (seek medical care immediately):

• Rash, blistering, peeling skin, or mucosal involvement

• Signs of kidney problems such as reduced urination, swelling, or elevated creatinine

• Severe confusion, hallucinations, decreased consciousness, or seizures

• Signs of TTP/HUS such as unusual bruising, bleeding, weakness, or neurological changes

• Anaphylaxis, angioedema, or difficulty breathing

While Taking Acyclovir

Tell your healthcare provider immediately if you:

• Develop a rash or skin reaction

• Experience neurological changes such as confusion or hallucinations

• Notice decreased urination or swelling

• Develop unusual bruising or bleeding

• Experience severe gastrointestinal symptoms

Maintain adequate hydration unless otherwise directed by your provider. 

Pregnancy and Breastfeeding

Acyclovir is classified as Pregnancy Category B. Registry data did not show an increased overall rate of birth defects; however, adequate and well-controlled studies in pregnant women are lacking. Use during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Acyclovir is excreted in breast milk. Use caution when administered to nursing mothers. 

Overdose

Overdose has been reported with ingestion of up to 20 grams. Symptoms may include agitation, coma, seizures, lethargy, and renal failure. Precipitation in renal tubules may occur. In cases of acute renal failure or anuria, hemodialysis may be beneficial. Seek emergency medical attention if overdose is suspected. 

Missed Dosage

If you miss a dose:

• Take it as soon as you remember

• Skip the missed dose if it is close to your next scheduled dose

• Do not double the next dose

Contact your healthcare provider if you are unsure how to proceed.

Storage

• Store at 20° to 25°C (68° to 77°F)

• Protect from light and moisture

• Dispense and store in a tight, light-resistant container

• Keep out of reach of children

Medication Disposal

Dispose of unused or expired medication according to local regulations. Do not flush medication unless instructed. Consult your pharmacist regarding safe disposal options.

Telemedicine Disclosure

This prescription may be issued via telemedicine. Contact your prescribing clinician immediately if you experience concerning or severe symptoms, or seek emergency medical care.

Disclaimer

This summary does not include all information about Acyclovir Tablets, USP and should not replace medical guidance. Always consult your healthcare provider or pharmacist for complete safety information, potential interactions, and individualized treatment recommendations.

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit MedWatch or call 1-800-FDA-1088.