Updated 11 February 2013


Acyclovir is indicated for the treatment of infections caused by the herpes virus such as shingles, genital herpes, chickenpox and fever blisters.


Acyclovir is the active ingredient of Zovirax, Activir, Acitop, Acitab, Adco-Acyclovir, Lovire, Cyclivex, Vyrohexal and Pharmacare-Acyclovir.

General information

Acyclovir is indicated for the treatment of infections caused by the herpes virus such as shingles, genital herpes, chickenpox and fever blisters. Acyclovir is not a cure for viral infections, but simply slows the virus down while allowing your immune system time to catch up. Treatment with acyclovir should start as soon as symptoms appear and before the appearance of any lesions. The medication is only effective if treatment is started within 48-72 hours of onset of the infection

How does Acyclovir work?

Acyclovir prevents the relevant herpes virus form multiplying by inhibiting enzymes needed for viral DNA replication in cells.

Fast facts

Drug schedule : Schedule 2 for topical applications; Schedule 4 in oral and injectable forms.

Available as: Acyclovir is available as tablets, oral liquid, cream, ointment and injection.

What does it do? Acyclovir is an antiviral drug

Overdose risk: Low

Dependence risk: Low

Is acyclovir available as a generic? Yes

Is acyclovir available on prescription only? No (the oral form will require a prescription)

User information

Onset of effect: Within 24 hours

Duration of action: Up to 8 hours

Dietary advice: Acyclovir can be taken with or without food. It is advised to take each dose with at least 250 ml of water and to drink at least 2 litres of water per day while being treated with this medication.

Stopping this medicine: Acyclovir should only be stopped once the prescribed course has been completed.

Prolonged use: Acyclovir is rarely used for prolonged periods. Drug resistance is possible with prolonged use.

Special precautions

Consult your doctor before using this drug if:

  • you have any kidney disease,
  • you had any allergic reactions to antiviral drugs before,
  • if you have reduced immunity, or
  • if you are taking any other medication.

Pregnancy: Avoid. Potential risk to the foetus has been reported. Consult your doctor before use, or if you are planning to fall pregnant.

Breastfeeding: Avoid. This medication is passed through breast milk and may affect your baby adversely. Consult your doctor before use.

Porphyria: This medication is safe to use.

Infants and children: A dosage adjustment may be needed.

Elderly: A dosage adjustment may be needed.

Driving and hazardous work: Acyclovir may cause dizziness. Avoid such activities until you know how it affects you.

Alcohol: Avoid concomitant use of alcohol.

Possible side effects

Side effect


Consult your doctor



Only if severe

In all cases

Oral form







Diarrhoea/stomach pain











Decreased urine



Topical form








Drug interactions:


Increased risk of acyclovir toxicity


Increased risk of acyclovir toxicity


Increased risk of acyclovir toxicity

Anticonvulsant drugs

Possible increased frequency of seizures


Increased risk of theophylline toxicity


Possibility of extreme lethargy

Aminoglycoside antibiotics

Increased risk of kidney damage

Disease interactions

Contact your doctor before taking acyclovir if you have kidney disease.

Overdose action

Exceeding the prescribed dose of acyclovir occasionally should not cause concern. In the case of intentional overdose immediate medical attention is required.

Recommended dosage

Oral form


Herpes simplex: 200 mg 5 times per day for 10 days in the case of first infection, and for 5 days with recurrent infections;

Varicrella zoster (chickenpox): 800 mg 5 times per day for 7 days

Herpes zoster (shingles): 800 mg 5 times per day for 7 days


Varicrella zoster (chickenpox): 20 mg/kg (maximum 800 mg/dose) 4 times per day for 5 days

Topical application

Apply to affected area 5 times per day

Interesting fact

Pharmacologist Gertrude B Elion was awarded the 1988 Nobel Prize in Medicine, partly for the development of acyclovir.

This material is not intended to substitute medical advice, but is for informational purposes only. Please consult a physician for specific treatment and recommendations.


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