Acyclovir

Name: Acyclovir

Canadian Brand Name

  1. Acyclovir

Other uses for this medicine

Acyclovir is also sometimes used to treat eczema herpeticum (a skin infection caused by the herpes virus) to treat and prevent herpes infections of the skin, eyes, nose, and mouth in patients with human immunodeficiency virus (HIV), and to treat oral hairy leukoplakia (condition that causes hairy white or gray-colored patches on the tongue or inside of the cheek).

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What is acyclovir, and how does it work (mechanism of action)?

Acyclovir is an antiviral drug, a synthetic nucleoside analogue, that has inhibitory activity (interferes with viral replication) against the herpes viruses, including herpes simplex 1 and 2 (cold sores and genital herpes), varicella-zoster (shingles and chickenpox), and Epstein-Barr virus (mononucleosis). Viruses take over living cells and reproduce themselves, often at the expense of the host cell. The acyclovir is converted to an active form by the virus itself, and the virus then uses the active form of acyclovir rather than the nucleoside it normally uses to manufacture DNA, a critical component of viral replication. Incorporation of active acyclovir into new viral DNA stops the production of the DNA. Virally infected cells absorb more acyclovir than normal cells and convert more of it to the active form, which prolongs its antiviral activity. The FDA approved acyclovir in March 1982.

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Patient information

Patients are instructed to consult with their physician if they experience severe or troublesome adverse reactions, they become pregnant or intend to become pregnant, they intend to breastfeed while taking orally administered ZOVIRAX (acyclovir) , or they have any other questions.

Patients should be advised to maintain adequate hydration.

Interactions for Acyclovir

Nephrotoxic Agents

Potential pharmacodynamic interaction (increased risk of renal dysfunction and/or reversible CNS manifestations); use concomitantly with caution.403 409

Specific Drugs

Drug

Interaction

Comments

Interferon

Additive or synergistic antiviral effect against HSV-1 in vitroa

Clinical importance unknown;a use with caution409

Methotrexate

Manufacturer states that IV acyclovir should be used with caution in patients receiving intrathecal methotrexate409

Probenecid

Decreased renal clearance of acyclovir403 409

Zidovudine

Neurotoxicity (profound drowsiness, lethargy) reported in at least 1 patient298

Monitor patients closely during concomitant therapy298

Allergies

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

In Summary

More frequently reported side effects include: nausea, phlebitis, vomiting, and inflammation at injection site. See below for a comprehensive list of adverse effects.

Usual Adult Dose for Herpes Simplex - Mucocutaneous/Immunocompetent Host

Treatment of First Episode of Genital Herpes:
200 mg orally every 4 hours 5 times a day for 10 days (manufacturer dosing)
400 mg orally 3 times a day for 5 to 10 days (CDC recommendation)

Severe Disease or Complications Requiring Hospitalization:
5 mg/kg IV every 8 hours for 5 days (manufacturer dosing)
5 to 10 mg/kg IV every 8 hours for 2 to 7 days or until clinical improvement is observed, followed by oral antiviral therapy to complete at least 10 days of total therapy (CDC recommendation)

Episodic (Intermittent) Therapy: Effective treatment requires therapy initiation within 1 day of lesion onset or during the prodrome preceding an episode/recurrence
200 mg orally every 4 hours 5 times a day for 5 days (manufacturer dosing)
400 mg orally 3 times a day for 5 days OR 800 mg orally 2 times a day for 5 days OR 800 mg orally 3 times a day for 2 days (CDC recommendations)

Comments:
-All patients with newly acquired genital herpes should receive antiviral therapy as first episodes can cause a prolonged clinical illness, even among persons with mild clinical manifestations initially; therapy should be initiated at the earliest sign or symptom of primary infection.
-IV therapy is indicated for patients with severe infection.
-CDC STD treatment Guidelines may be consulted for additional guidance.

Use: For the initial treatment and recurrent episodes of mucosal and cutaneous herpes simplex (HSV-1 and HSV-2).

Usual Adult Dose for Herpes Simplex - Mucocutaneous/Immunocompromised Host

Concomitant HIV infection:

-Treatment of First Episode of Genital Herpes:
400 mg orally 3 times a day for 5 to 10 days (guideline recommendation)
Duration of therapy: 5 to 10 days

-Severe Disease:
5 mg/kg IV every 8 hours after lesions begin to regress, may change to oral therapy; continue treatment until lesions have completely healed (guideline recommendation)

Episodic (Intermittent) Therapy: Effective treatment requires therapy initiation within 1 day of lesion onset or during the prodrome preceding an episode/recurrence
400 mg orally 3 times a day for 5 to 14 days

Comments:
-Immunocompromised patients can have prolonged or severe episodes of genital, perianal, or oral herpes.
-Clinical manifestations of genital herpes may worsen during immune reconstitution early after initiation of antiretroviral therapy.
-Suppressive or episodic therapy with oral antiviral agents is effective in decreasing the clinical manifestations of HSV in persons with HIV infection.
-Guidelines for the Prevention and Treatment of Opportunistic Infections Among HIV- Infected Adults and Adolescents may be consulted for additional guidance.

Use: For the treatment of initial and recurrent mucosal and cutaneous herpes simplex (HSV-1 and HSV-2) in immunocompromised patients.

Usual Adult Dose for Herpes Zoster

800 mg orally every 4 hours 5 times a day for 7 to 10 days

Immunocompromised host:
10 mg/kg IV every 8 hours for 7 days

Concomitant HIV infection:
-Localized Dermatomal: 800 mg orally 5 times a day for 7 to 10 days (alternative therapy; oral valacyclovir or famciclovir are preferred therapy)
-Extensive Cutaneous Lesion or Visceral Involvement: 10 to 15 mg/kg IV every 8 hours until clinical improvement (i.e. no new vesicle formation or improvement of signs and symptoms of visceral disease), then switch to oral therapy
Duration of therapy: 7 to 14-day course (oral plus IV)

Comments:
-Treatment should be initiated as soon as possible after a diagnosis of herpes zoster; parenteral dosing is based on ideal body weight (IBW).
-Oral acyclovir therapy should be considered an alternative therapy to treat acute localized dermatomal herpes zoster in HIV-infected adults according to the Guidelines for the Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescents; IV acyclovir is preferred therapy with extensive cutaneous lesion or visceral involvement.

Use: For the acute treatment of herpes zoster (shingles).

Usual Pediatric Dose for Herpes Simplex Labialis

Concomitant HIV infection:

20 mg/kg orally 4 times a day for 5 days
Maximum dose: 400 mg

Adolescents: 400 mg orally 3 times a day for 5 to 10 days

Comments:
-The safety and efficacy of buccal tablets in pediatric patients has not been evaluated.
-Use of buccal tablets in younger children may present a choking risk.
-Guidelines for the Prevention and Treatment of Opportunistic Infections Among HIV- Infected Adults and Adolescents may be consulted for additional guidance.

Use: For the treatment of recurrent herpes simplex labialis (cold sores).

Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Nausea, vomiting, diarrhea, headache, and a general unwell feeling. Buccal tablets may cause mouth pain. Rarely, acyclovir may affect your kidneys or cause a bleeding disorder.
  • May not be suitable for some people, including those with kidney problems, who are immunosuppressed, taking certain medications, or in those who are dehydrated.
  • Acyclovir is usually dosed five times daily.
  • May interact with a number of other medications including probenecid, other antivirals, medications for bowel disease, injectable osteoporosis medications, and analgesics.

Notes: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. For a complete list of all side effects, click here.

Acyclovir Breastfeeding Warnings

Adverse effects in breast-feeding infants associated with exposure to this drug via breast milk have not been reported in the literature. With the highest maternal dosage, the expected infant dose is about 1% of a typical infant dose.

Use caution Excreted into human milk: Yes Comments: This drug has been used without apparent harmful effects

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