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 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.

Immune system disorders:
 
Very rare:
 Immediate hypersensitivity reactions including angioedema and urticaria.
 
Eye disorders:
 
Very common:
 Superficial punctate keratopathy.
 

This did not necessitate an early termination of therapy and healed without apparent sequelae.

Common:
 Transient mild stinging of the eye occurring immediately following application, conjunctivitis.
 
Rare:
 Blepharitis.
 

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
No untoward effects would be expected if the entire contents of the tube containing 135 mg of aciclovir were ingested orally. However, the accidental, repeated overdose of oral aciclovir, over several days, has resulted in gastrointestinal effects (nausea and vomiting) and neurological effects (headache and confusion). Aciclovir is dialysable by haemodialysis.

5. Pharmacological properties
5.1 Pharmacodynamic properties
Aciclovir is an antiviral agent which is highly active in vitro against herpes simplex (HSV) types I and II, but its toxicity to mammalian cells is low.

Aciclovir is phosphorylated to the active compound aciclovir triphosphate after entry into a herpes infected cell. The first step in this process requires the presence of the HSV coded thymidine kinase. Aciclovir triphosphate acts as an inhibitor of, and substrate for, herpes specified DNA polymerase, preventing further viral DNA synthesis without affecting normal cellular processes

5.2 Pharmacokinetic properties
Aciclovir is rapidly absorbed from the ophthalmic ointment through the corneal epithelium and superficial ocular tissues, achieving antiviral concentrations in the aqueous humor. It has not been possible by existing methods to detect aciclovir in the blood after topical application to the eye. However, trace quantities are detectable in the urine. These levels are not therapeutically significant.

5.3 Preclinical safety data
The results of a wide range of mutagenicity tests in vitro and in vivo indicate that aciclovir does not pose a genetic risk to man.

Aciclovir was not found to be carcinogenic in long-term studies in the rat and the mouse.

Largely reversible adverse effects on spermatogenesis in association with overall toxicity in rats and dogs have been reported only at doses of aciclovir greatly in excess of those employed therapeutically. Two-generation studies in mice did not reveal any effect of orally administered aciclovir on fertility.

Systemic a