Zovirax Cream is contraindicated in patients known to be hypersensitive to aciclovir, valaciclovir, propylene glycol or any of the excipients of Zovirax Cream listed in section 6.1.
Zovirax Cream is not recommended for application to mucous membranes such as in the mouth, eye or vagina, as it may be irritant.
Particular care should be taken to avoid accidental introduction into the eye.
In severely immunocompromised patients (e.g. AIDS patients or bone marrow transplant recipients) oral Zovirax dosing should be considered. Such patients should be encouraged to consult a physician concerning the treatment of any infection.
The excipient propylene glycol can cause skin irritations and the excipient cetyl alcohol can cause local skin reactions (e.g. contact dermatitis).
Zovirax Cream contains a specially formulated base and should not be diluted or used as a base for the incorporation of other medicaments.
No clinically significant interactions have been identified.
A post-marketing aciclovir pregnancy registry has documented pregnancy outcomes in women exposed to any formulation of Zovirax. 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.
The use of Zovirax Cream should be considered only when the potential benefits outweigh the possibility of unknown risks however the systemic exposure to aciclovir from topical application of Zovirax Cream is very low.
Effects in non-clinical studies were observed only at exposures considered sufficiently in excess of the maximum human exposure to indicate little relevance to clinical use (see section 5.3)
Limited human data show that the drug does pass into breast milk following systemic administration. However, the dosage received by a nursing infant following maternal use of Zovirax Cream would be insignificant.
There is no information on the effect of aciclovir on human female fertility.
In a study of 20 male patients with normal sperm count, oral aciclovir administered at doses of up to 1g per day for up to six months has been shown to have no clinically significant effect on sperm count, motility or morphology.
See Clinical Studies in section 5.2
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.
Very rare: Immediate hypersensitivity reactions including angioedema and urticaria.
Uncommon: Transient burning or stinging following application of Zovirax 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.
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.