In severely immunocompromised patients (eg after marrow transplant) or in patients with impaired absorption from the gut, consideration should be given to intravenous dosing.

Dosing should begin as early as possible after the start of an infection: treatment of herpes zoster yields better results if initiated as soon as possible after the onset of the rash. Treatment of chickenpox in immunocompetent patients should begin within 24 hours after onset of the rash.

Dosage in Children

Treatment of herpes simplex infections, and prophylaxis of herpes simplex infections in the immunocompromised: Children aged two years and over should be given adult dosages and children below the age of two years should be given half the adult dose.

For treatment of neonatal herpes virus infections, intravenous acyclovir is recommended.

Treatment of varicella infections:

6 years and over: 800mg Zovirax four times daily.

2 - less than 6 years: 400mg Zovirax four times daily.

Under 2 years: 200mg Zovirax four times daily.

Treatment should continue for five days.

Dosing may be more accurately calculated as 20mg/kg body weight (not to exceed 800mg) Zovirax four times daily.

No specific data are available on the suppression of herpes simplex infections or the treatment of herpes zoster infections in immunocompetent children.

Zovirax Double Strength Suspension may be diluted with an equal volume of either Syrup BP or Sorbitol Solution (70%) (non-crystallising) BP. The diluted product is stable for 4 weeks at 25°C but it is recommended that all dilutions are freshly prepared.

Dosage in the Elderly

The possibility of renal impairment in the elderly must be considered and the dosage should be adjusted accordingly (see Dosage in Renal Impairment below).

Adequate hydration of elderly patients taking high oral doses of aciclovir should be maintained.

Dosage in Renal Impairment

Caution is advised when administering aciclovir to patients with impaired renal function. Adequate hydration should be maintained.

In the management of herpes simplex infections in patients with severe renal impairment (creatinine clearance less than 10 ml/minute) an adjustment of dosage to 200 mg aciclovir twice daily at approximately twelve-hourly intervals is recommended.

In the treatment of varicella and herpes zoster infections it is recommended to adjust the dosage to 800mg aciclovir twice daily at approximately twelve-hourly intervals for patients with severe renal impairment (creatinine clearance less than 10ml/minute), and to 800mg aciclovir three times daily at intervals of approximately eight hours for patients with moderate renal impairment (creatinine clearance in the range 10 to 25ml/minute).

4.3 Contraindications
Hypersensitivity to aciclovir or valaciclovir, or to any of the excipients listed in section 6.1.

4.4 Special warnings and precautions for use
Use in patients with renal impairment and in elderly patients:

Aciclovir is eliminated by renal clearance, therefore the dose must be adjusted in patients with renal impairment (see 4.2 Posology and Method of Administration). Elderly patients are likely to have reduced renal function and therefore the need for dose reduction must be considered in this group of patients. Both elderly patients and patients with renal impairment are at increased risk of developing neurological side effects and should b