Acyclovir Vs. Valacyclovir: Drug Comparison

Acyclovir is an antiviral medication used to treat infections caused by herpes viruses, such as herpes simplex (cold sores, genital herpes), varicella-zoster (chickenpox), and shingles. It works by inhibiting viral DNA replication, thereby slowing the spread of the virus and helping the body fight the infection. FDA-approved indications include treatment of herpes simplex infections, shingles, and chickenpox. Off-label uses may include prevention of recurrent herpes outbreaks or managing Epstein-Barr virus infections. Acyclovir is available in forms including tablets, capsules, liquid suspensions, topical creams, and intravenous (IV) solutions, with common side effects including nausea, headache, and diarrhea. Drug interactions are minimal. Doses and length of treatment are different depending upon what acyclovir is being used to treat. Acyclovir should be used cautiously in people who have chronic kidney issues.

Valacyclovir is the active ingredient in the brand-name medication Valtrex^®. The information below is about brand name Valtrex. According to the FDA, “Generic medicines use the same active ingredients as brand-name medicines and work the same way, so they have the same risks and benefits as the brand-name medicines.”

Valtrex (valacyclovir) is an antiviral medication used to treat infections caused by herpes viruses, including herpes simplex (cold sores and genital herpes), shingles (herpes zoster), and chickenpox (varicella). It works by inhibiting the replication of viral DNA, slowing the spread of the virus and reducing symptoms. Its FDA-approved indications include the treatment of cold sores, genital herpes, shingles, and chickenpox, as well as the suppression of recurrent genital herpes and the reduction of transmission of herpes to sexual partners. Valtrex is available in tablet form, typically taken once or twice daily depending on the condition being treated. Common side effects include headache, nausea, and abdominal pain. Caution is advised in patients with kidney issues, as the drug may cause kidney toxicity in those with impaired renal function.

Synthetic nucleoside analogue

Deoxynucleoside analogue DNA polymerase inhibitor

Acyclovir is indicated for:

• The acute treatment of herpes zoster (shingles)

• The treatment of initial episodes and the management of recurrent episodes of genital herpes

• The treatment of chickenpox (varicella)

Valtrex (valacyclovir hydrochloride) is indicated for:

Adult patients:

• Cold sores (herpes labialis)

• Genital herpes

  • Treatment in immunocompetent patients (initial or recurrent episode)

  • Suppression in immunocompetent or HIV-1−infected patients

  • Reduction of transmission

• Herpes zoster

Pediatric patients:

• Cold sores (herpes labialis)

• Chickenpox

• Typically taken orally with specific dosing depending on what's being treated

• Comes in 400 mg and 800 mg tablets

• Typically taken orally once or twice daily

• Comes in 500 mg (unscored) and 1,000 mg (partially scored) tablets

The most frequent side effects in patients taking acyclovir for herpes simplex, herpes zoster, or chickenpox were:

• Nausea

• Vomiting

• Diarrhea

• Headache

• Malaise

The most common adverse reactions reported in at least one indication by greater than 10% of adult subjects treated with Valtrex and more commonly than in subjects treated with placebo are:

• Headache

• Nausea

• Abdominal pain

The only adverse reaction occurring in greater than 10% of pediatric subjects aged less than 18 years was:

• Headache

• Hypersensitivity to acyclovir or valacyclovir

• Drug interactions: probenecid

• Hypersensitivity to valacyclovir (e.g., anaphylaxis), acyclovir, or any component of the formulation

• Acyclovir tablets are intended for oral ingestion only

• Dosage adjustment is recommended when administering acyclovir tablets to patients with renal impairment

• Pregnancy: Acyclovir should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus

• Breastfeeding: Acyclovir should be administered to a nursing mother with caution and only when indicated

• Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS)

• Acute renal failure

• Central nervous system adverse reactions (e.g., agitation, hallucinations, confusion, and encephalopathy)

*This information is from the acyclovir label used by Camber Pharmaceuticals, Inc. See the Full Prescribing Information for more complete information. Acyclovir may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient acyclovir.

*This information is from the label for brand name Valtrex^®. See the Full Prescribing Information for more complete information. Valacyclovir, the active ingredient in Valtrex, may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient valacyclovir.