Brand Name - Zovirax

  • Type of Drug: Antiviral.
  • Prescribed for: Treatment and prevention of serious, frequently recurring herpes simplex infections of the genitals, mucous membrane tissues, and central nervous system. It also works against shingles (herpes zoster) and chickenpox (varicella). Other viral infections for which Acyclovir may be prescribed are nongenital herpes simplex infections, herpes simplex and cytomegalovirus (CMV) infections in immunocompromised patients, and varicella pneumonia.

General Information

Acyclovir is the only oral drug that can reduce the rate of growth of the herpes virus and its relatives, Epstein-Barr virus, CMV, and varicella. Both oral Acyclovir and oral Ganciclovir work against CMV; other drugs, given by intravenous injection, may be used for these infections, but they are usually reserved for patients with AIDS or cancer, or other immunocompromised patients. Acyclovir does not cure herpes, but it can reduce pain associated with the disease’ and may help herpes sores heal faster. It may also reduce the rate at which new herpes lesions form. Acyclovir does not affect common-cold viruses.

Acyclovir is selectively absorbed into cells that are infected with the herpes simplex virus. There, it is converted into its active form and works by interfering with the reproduction of viral DNA, slowing the growth of existing viruses. It has little effect on treating recurrent infections. The drug must be given by intravenous injection in a hospital or doctor’s office or by mouth to treat both local and systemic symptoms. Local symptoms can be treated with the ointment alone. The capsules can be taken every day to reduce the number and severity of herpes attacks in people who usually suffer 10 or more attacks a year, and may be used to treat intermittent attacks as they occur, but the drug must be started as soon as possible to have the greatest effect.

Cautions and Warnings

Acyclovir ointment should not be applied to your skin if you have had an allergic reaction to it or to the major component of the ointment base, Polyethylene Glycol. Acyclovir ointment should not be used to treat a herpes infection of the eye because it is not specifically made for that purpose. Some people develop tenderness, swelling, or bleeding of the gums while taking Acyclovir. Regular brushing, flossing, and gum massage may help prevent these conditions.

Long-term high doses of Acyclovir have caused reduced sperm count in animals, but this effect has not yet been reported in men.

Do not apply inside the vagina because the Polyethylene Glycol base can irritate and cause swelling of those sensitive tissues.

Possible Side Effects

Ointment Form

  • Most common: mild burning, irritation, rash, and itching. Women are 4 times more likely to experience burning than men, and it is more likely to occur when applied during an initial herpes attack than during a recurrent attack.


  • Most common: dizziness, headache, diarrhea, nausea, and vomiting.
  • Less common: loss of appetite, stomach gas, constipation, fatigue, rash, feelings of ill health, leg pains, sore throat, a bad taste in the mouth, sleeplessness, and fever.Other: aching joints, weakness, and tingling in the hands or feet.

Intravenous Form

  • Other: pain or inflammation at the injection site, liver inflammation, confusion, hallucinations, tremors, agitation, seizures, coma, anemia, kidney damage, blood in the urine, pain or pressure on urination, loss of bladder control, abdominal pains, fluid in the lungs, and fingertips turning blue.

Drug Interactions

  • Do not apply Acyclovir together with any bther ointment or topical medicine.
  • Oral Probenecid may decrease the elimination of Acyclovir from your body, which increases Acyclovir’s blood levels when it is taken by mouth or by injection, and thus increases the chance of side effects.
  • Taking Acyclovir and Zidovudine (AZT) together may lead to severe drowsiness and lethargy.

Food Interactions

Acyclovir may be taken with food if it upsets your stomach.

Usual Dose

For maximum benefit, treatment should be started as soon as possible. If you have kidney disease, your doctor should adjust your dose according to the degree of functional loss.’

Adult: For a genital herpes attack: 200 mg every 4 hours, 5 times per day for 10 days. For recurrent infections: 400 mg twice a day or 200 mg 2 to 5 times per day. As suppressive therapy for people who suffer from chronic herpes infection: 400 to 800 mg per day, every day. For herpes zoster infections: 800 mg, 5 times per day for 7 to 10 days.

Child: Acyclovir is not recommended in children under age 2, but it has been given to children in daily doses as high as 36 mg per pound of body weight without any unusual side effects.

Apply the ointment every 3 hours, 6 times per day for 7 days; apply enough to cover all visible lesions. About 1/2 inch of Acyclovir ointment should cover about 4 square inches of skin lesions. Your doctor may prescribe a longer course of treatment to prevent the delayed formation of new lesions during the duration of an attack.


Acyclovir overdose is likely to lead to kidney damage due to the deposition of drug crystals in the kidney. Divided oral doses of up to 4.8 grams per day for 5 days have been taken without serious adverse effects.

The chance of experiencing toxic side effects from swallowing Acyclovir ointment is quite small because there are only 50 mg of drug per gram of ointment.

Observe the overdose victim for side effects and call your poison control center for more detailed information.

Special Information

Women with genital herpes have an increased risk of cervical cancer. Check with your doctor about the need for an annual Pap smear.

Use a finger cot or rubber glove when applying the ointment to protect against inadvertently spreading the virus. Be sure to apply the medicine exactly as directed and to completely cover all lesions. If you skip several doses or a day or more of treatment, the therapy will not exert its maximum effect. Keep affected areas clean and dry. Loose-fitting clothing will help to avoid irritation of a healing herpes lesion.

Herpes can be transmitted even if you do not have symptoms of active disease. To avoid transmitting the condition td a sex partner, do not have intercourse while visible herpes lesions are present. A condom offers some protection against transmission of the virus, but spermicidal products and diaphragms will not. Acyclovir alone also does not protect against spreading the herpes virus.

Call your doctor if the drug does not relieve your condition, if side effects become severe or intolerable, or if you become pregnant or want to begin breast-feeding. Check with your dentist if you notice swelling or tenderness of the gums.

Special Populations

Acyclovir crosses into the circulation of a developing fetus. Very small amounts of the drug are absorbed into the blood after application of the ointment. Animal studies have shown that large doses (up to 125 times the human dose) cause damage to both mother and developing fetus. While there is no information to indicate that Acyclovir affects a developing fetus, you should not use it during pregnancy unless it is specifically prescribed by your doctor and the possible benefit outweighs the possible risk of taking it.
Acyclovir passes into breast milk in concentrations up to 4 times the concentration in blood, and it has been found in the urine of a nursing infant. No drug side effects have been found in nursing babies, but mothers who must take this drug should consider bottle-feeding their infants.

People over 50 years of age with shingles tend to have more severe attacks of shingles and may benefit more from Acyclovir treatment if the medicine is started within 48 to 72 hours of the appearance of the first rash. Seniors with reduced kidney function should be given a lower oral dose than younger adults to account for normal reductions in kidney function that occur with aging.