A post-marketing aciclovir pregnancy registry has documented pregnancy outcomes in women exposed to any formulation of aciclovir. The registry findings have not shown an increase in the number of birth defects amongst aciclovir exposed subjects compared with the general population, and any birth defects showed no uniqueness or consistent pattern to suggest a common cause. Systemic administration of aciclovir in internationally accepted standard tests did not produce embryotoxic or teratogenic effects in rabbits, rats or mice. In a non-standard test in rats, foetal abnormalities were observed but only following such high subcutaneous doses that maternal toxicity was produced. The clinical relevance of these findings is uncertain.

Breast-Feeding

Following oral administration of 200mg aciclovir five times a day, aciclovir has been detected in breast milk at concentrations ranging from 0.6-4.1 times the corresponding plasma levels. These levels would potentially expose nursing infants to aciclovir dosages of up to 0.3mg/kg/day. Caution is therefore advised if aciclovir is to be administered to a nursing mother.

4.7 Effects on ability to drive and use machines
The clinical status of the patient and the adverse event profile of aciclovir should be borne in mind when considering the patients's ability to drive or operate machinery.

As aciclovir administration is occasionally associated with drowsiness and somnolence (usually in patients receiving high doses or with impaired renal function), patients should make sure that they are not affected before driving or using machinery.

There have been no studies to investigate the effect of aciclovir on driving performance or the ability to operate machinery. Further, a detrimental effect on such activities cannot be predicted from the pharmacology of the active substance.

4.8 Undesirable effects
The frequency categories associated with the adverse events below are estimates. For most events, suitable data for estimating incidence were not available. In addition, adverse events may vary in their incidence depending on the indication.

An estimate of the frequency of undesirable effects has been included though this is not certain for all adverse effects. The following convention has been used for the classification of undesirable effects in terms of frequency: very common (>1/10), common (>1/100, <1/10), uncommon (>1/1000, <1/100), rare (>1/10000, <1/1000, very rare (<1/10000).

Blood and the lymphatic system disorders

Very rare: Anaemia, leucopenia and thrombocytopenia.

Immune system disorders

Rare: Anaphylaxis.

Nervous system disorders

Common: Dizziness and headache.

Very rare: Reversible neurological reactions including agitation, tremor, ataxia, dysarthria, psychotic symptoms, encephalopathy, drowsiness, confusional states, hallucinations, somnolence, convulsions, coma and malaise. These effects were usually r