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.

Lactation:

As there is only minimal systemic absorption of aciclovir, adverse effects on the infant during lactation are unlikely. Limited human data show that the drug does pass into breast milk following systemic administration. The dosage received by a nursing infant following maternal use of aciclovir cream would be insignificant.

4.7 Effects on ability to drive and use machines
Virasorb Cold Sore Cream is unlikely to impair a patient's ability to drive or to use machines.

4.8 Undesirable effects
The following convention has been used for the classification of undesirable effects in terms of frequency:-

Very common ≥1/10, common ≥1/100 and <1/10, uncommon 1/1000 and <1/100, rare ≥1/10,000 and <1/1000, very rare <1/10,000.

Clinical trial data have been used to assign frequency categories to adverse reactions observed during clinical trials with aciclovir 3% ophthalmic ointment. Due to the nature of the adverse events observed, it is not possible to determine unequivocally which events were related to the administration of the drug and which were related to the disease. Spontaneous reporting data has been used as a basis for allocating frequency for those events observed post-marketing.

Skin and subcutaneous tissue disorders
 
Uncommon:
 Transient burning or stinging following application of aciclovir cream. Mild drying or flaking of the skin. Itching.
 
Rare:
 Erythema. Contact dermatitis following application. Where sensitivity tests have been conducted, the reactive substances have most often been shown to be components of the cream rather than aciclovir. The contact dermatitis is characterised by the occurrence of the cutaneous reactions as described above, with a widespread distribution.

 
Immune system disorders
 
Very rare:
 Immediate hypersensitivity reactions including angioedema and urticaria.
 

Reporting of suspected adverse reactions

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.
4.9 Overdose
As only about 0.1% of the aciclovir applied to the skin is detectable in the plasma, overdose is unlikely. No untoward effects would be expected if the entire contents of the tube containing 100 mg of aciclovir cream were ingested orally.

5. Pharmacological properties
5.1 Pharmacodynamic propertie