Brand name: Zovirax
Drug class: Antivirals
VA class: DE103
Chemical name: 9-[(2-Hydroxyethoxy)methyl]guanine
CAS number: 59277-89-3

Medically reviewed by Drugs.com on Jun 21, 2023. Written by ASHP.

Introduction

Antiviral; purine nucleoside analog derived from guanine.

Uses for Acyclovir (Topical)

Herpes Labialis

Treatment of recurrent herpes labialis (perioral herpes, cold sores, fever blisters) in immunocompetent adults and children ≥12 years of age.

Genital Herpes

Has been used for topical treatment of initial episodes of genital herpes in immunocompromised or immunocompetent adults.

Topical antivirals generally not recommended for treatment of genital herpes. CDC and others recommend oral acyclovir, oral famciclovir, or oral valacyclovir as drugs of choice for treatment of initial episodes of genital herpes and for episodic treatment or chronic suppressive therapy of recurrent genital herpes.

Has not been effective for prevention of recurrent genital herpes when initiated immediately following development of prodromal symptoms (e.g., itching, burning, tingling, numbness).

No evidence that topical acyclovir prevents transmission of infection to other individuals.

Mucocutaneous Herpes Simplex Virus (HSV) Infections

Has been used for topical treatment of non-life-threatening, nongenital, mucocutaneous HSV infections in immunocompromised adults; efficacy of such treatment not established in immunocompetent individuals.

Systemic therapy (e.g., oral or IV acyclovir) usually recommended for treatment of mucocutaneous HSV infections.

Should not be used for prevention of recurrent HSV infections. No evidence that topical acyclovir prevents transmission of HSV or prevents recurrent HSV infections when applied in the absence of signs and symptoms of infection.

Acyclovir (Topical) Dosage and Administration

Administration

Topical Administration

Apply topically to lesions of the lips and surrounding skin as a 5% cream or ointment, and apply to lesions of the skin as a 5% ointment.

Do not apply 5% cream or ointment in or near the eyes. For external use only; do not apply inside mouth or nose.

The 5% cream should be used only for treatment of herpes labialis (perioral herpes, cold sores, fever blisters) and should not be used to treat genital herpes.

After applying 5% cream, rub until the cream disappears. Do not use with occlusive dressings unless otherwise directed by clinician. Do not bathe, shower, or swim immediately after application.

When applying 5% ointment, use finger cot or rubber glove to prevent autoinoculation of other sites and transmission of herpes virus to other individuals.

Dosage

Pediatric Patients

Herpes Labialis

Topical

Children ≥12 years of age: Apply 5% cream to affected area 5 times daily for 4 days. Use sufficient quantity to adequately cover lesions or symptomatic area (e.g., area with tingling).

Initiate at the earliest sign or symptom of herpes labialis (i.e., during the prodrome or when lesions appear).

Do not exceed recommended dosage, frequency, and duration of therapy.

Adults

Herpes Labialis

Topical

Apply 5% cream to affected area times 5 times daily for 4 days. Use sufficient quantity to adequately cover lesions or symptomatic area (e.g., area with tingling).

Initiate at the earliest sign or symptom of herpes labialis (i.e., during the prodrome or when lesions appear).

Do not exceed recommended dosage, frequency, and duration of therapy.

Genital Herpes

Treatment of First Episodes

Topical

Rub 5% ointment gently into the affected area every 3 hours 6 times daily for 7 days. Use sufficient quantity to adequately cover all lesions; usual dose varies according to total lesion area but should approximate a 1.25-cm (0.5-inch) ribbon of ointment for a skin surface area of 2.5 cm² (4 inch²).

Initiate at the earliest sign or symptom of genital herpes (i.e., during the prodrome or when lesions appear).

Do not exceed recommended dosage, frequency, and duration of therapy.

Mucocutaneous Herpes Simplex Virus (HSV) Infections

Non-life-threatening, Nongenital, Mucocutaneous HSV Infections

Topical

Immunocompromised adults: Rub 5% ointment gently into the affected area every 3 hours 6 times daily for 7 days. Use sufficient quantity to adequately cover all lesions; usual dose varies according to total lesion area but should approximate a 1.25-cm (0.5-inch) ribbon of ointment for a skin surface area of 2.5 cm² (4 inch²).

Do not exceed recommended dosage, frequency, and duration of therapy.

Cautions for Acyclovir (Topical)

Contraindications

• Hypersensitivity to acyclovir, valacyclovir, or any ingredient in the formulations.

Warnings/Precautions

Sensitivity Reactions

Potential for irritation and contact sensitization with 5% cream; contact dermatitis reported.

General Precautions

Immunocompromised Patients

Efficacy of 5% cream not established in immunocompromised patients.

Viral Resistance

Clinically important viral resistance associated with use of topical acyclovir not reported to date. The possibility of such resistance should be considered, especially in those with poor clinical response.

Specific Populations

Pregnancy

Category B.

Lactation

Not known whether distributed into human milk after topical application, but systemic exposure after topical administration is minimal. Distributed into human milk following oral or IV administration.

Women with active herpetic lesions near or on the breast should refrain from breast-feeding.

Pediatric Use

Safety and efficacy of 5% cream not established in children <12 years of age.

Safety and efficacy of 5% ointment not established in children.

Geriatric Use

Insufficient experience in patients ≥65 years of age to determine whether geriatric patients respond differently than younger adults. Clinical experience has not revealed age-related differences.

Common Adverse Effects

Local effects such as mild pain, transient burning or stinging, pruritus, cracked or dry lips, desquamation, dry or flaking skin.

Drug Interactions

No interactions identified to date when topical acyclovir used concomitantly with other topical or systemic drugs. Because systemic absorption appears to be minimal following topical application to intact skin, drug interactions between topical acyclovir and systemically administered drugs are unlikely.

Acyclovir (Topical) Pharmacokinetics

Absorption

Bioavailability

Not appreciably absorbed into systemic circulation following topical application to intact skin.

Not detected in blood or urine of immunocompromised adults following application of 5% ointment to intact skin (4.5 inch²) at a dosage of 25 mg (1-cm ribbon) 4 times daily for 7 days.

Following topical application of 5% ointment in patients with localized varicella-zoster virus (VZV) infections, plasma acyclovir concentrations were ≤0.28 mcg/mL or ≤0.78 mcg/mL in those with normal or impaired renal function, respectively.

Following repeated (5 times daily for 4 days) topical application of 5% cream to intact skin (710 cm²) in adult males, plasma acyclovir concentrations measured 1 hour after the final application were undetectable or just above the limits of detection.

Systemic absorption of 5% cream not evaluated in children <18 years of age.

Distribution

Not fully characterized following topical application.

Crosses placenta following oral or IV administration.

Not known if drug or its metabolites distributed into human milk following topical application. Following oral or IV administration, distributed into human milk in concentrations greater than concurrent maternal plasma concentrations.

Elimination

Metabolism

Not fully characterized following topical application.

Converted in vivo to the pharmacologically active triphosphate metabolite.

Elimination Route

Following systemic absorption, excreted principally in urine.

Following topical application of 5% ointment in immunocompromised patients with localized VZV infections, ≤9.4% of total daily dose excreted in urine.

Following repeated (5 times daily for 4 days) topical application of 5% cream to intact skin (710 cm²) in adult males, 0.04% of the daily dose was detected in urine within 24 hours.

Stability

Storage

Topical

Cream

≤25°C (may be exposed to 15°–30°C).

Ointment

15°–25°C in dry place.

Actions and Spectrum

• Converted in vivo to the pharmacologically active triphosphate metabolite.

• Exerts antiviral effect by interfering with DNA synthesis and inhibiting viral replication.

• Active against various Herpesviridae, including herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) and varicella-zoster virus (VZV). Also active against cytomegalovirus (CMV), Epstein-Barr virus (EBV), and herpes simiae, but these viruses not generally associated with dermatologic infections.

• Resistance to acyclovir reported in HSV and VZV.

• Some acyclovir-resistant HSV and VZV are cross-resistant to penciclovir.

Advice to Patients

• Importance of using only for condition prescribed. Advise patient that 5% cream is only for treatment of herpes labialis (perioral herpes, cold sores, fever blisters) and should not be used to treat genital herpes.

• Ensure that the affected areas are clean and dry before application.

• Do not apply to unaffected skin or inside the mouth or nose. For external use only.

• Importance of avoiding contact with eyes.

• Importance of avoiding use of occlusive dressings unless otherwise directed by clinician.

• Importance of washing hands before and after application. Advise patients not to bathe, shower, or swim immediately after application.

• Advise patients not to apply other topical products (e.g., cosmetics, lip balms, sunscreens, other topical medications) to treated areas unless otherwise directed by clinician.

• For treatment of herpes labialis, importance of applying to affected areas as directed and at the first sign or symptom (e.g., tingling, redness, bump, itching).

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs.

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

• Importance of advising patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

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