Product Overview

Acyclovir USP 5% is a topical antiviral medication used to treat viral infections caused by the herpes simplex virus (HSV). It helps to relieve symptoms and promote the healing of sores and blisters. It is widely used for cutaneous herpes simplex infections, including cold sores and genital herpes.

Indications

Acyclovir USP 5% is indicated for:

• Herpes labialis (cold sores) caused by HSV-1.
• Genital herpes (herpes simplex virus type 2, HSV-2) for both initial and recurrent episodes.
• Herpes zoster (shingles) for topical relief, though systemic therapy is often more effective.
• Herpes simplex infections of the skin in immunocompromised patients.

Dosage and Administration

• Dosage Form: Topical cream or ointment
• Standard Strength: 5% Acyclovir concentration
• Administration:
  • The cream or ointment should be applied thinly to the affected area five times a day (approximately every 4 hours), sparing the nighttime dose.
  • It should be started as early as possible following the onset of symptoms, preferably at the first sign of a lesion (e.g., tingling, itching).
  • Treatment typically lasts 5 to 10 days, or as directed by a healthcare provider.

Mechanism of Action

• Acyclovir is a synthetic nucleoside analog that specifically targets and inhibits viral DNA polymerase, an enzyme essential for viral replication.
• It is converted into its active form, acyclovir triphosphate, by viral enzymes in infected cells, selectively inhibiting viral DNA synthesis without affecting normal cellular processes.

Pharmacokinetics

• Absorption: Minimal systemic absorption when applied topically, which limits the risk of systemic side effects.
• Onset of Action: Symptomatic relief is usually observed within a few days of starting treatment, though complete lesion healing may take up to 10 days.
• Excretion: Systemic absorption, if any, is excreted primarily through the kidneys.

Safety and Precautions

• Contraindications: Known hypersensitivity to Acyclovir, valacyclovir, or any of the excipients.
• Warnings:
  • Use only on external skin lesions and avoid contact with eyes, inside the mouth, or mucous membranes.
  • It does not cure herpes infections or prevent transmission, so patients should still take precautions to prevent spread, especially in active phases.
  • Limited use in pregnancy and lactation unless the potential benefits outweigh the risks, as determined by a healthcare provider.
  • May not be as effective in severely immunocompromised patients, who may require systemic antiviral therapy.

Adverse Reactions

Common side effects include:

• Mild burning, stinging, or itching at the application site
• Dryness, flakiness, or redness of the skin
• Rare allergic reactions like rash, swelling, or hypersensitivity at the application site

Clinical Benefits

Clinical trials and real-world use have shown that Acyclovir USP 5%:

• Effectively accelerates the healing of herpes lesions.
• Reduces the duration of pain, burning, and itching associated with cold sores and genital herpes.
• Shortens the time to crusting of lesions.

Storage

• Store at room temperature, away from excessive heat and moisture.
• Keep tightly closed when not in use and out of reach of children.

Regulatory Classification

• Prescription or OTC: It is available by prescription in many countries and as an over-the-counter medication in some for the treatment of cold sores.
• Classified as an antiviral agent for topical application.