Econazole

Econazole acts by damaging fungal cell membranes. The permeability of the fungal cell is increased. Sub-cellular membranes in the cytoplasm are damaged. The site of action is most probably the unsaturated fatty acid acyl moiety of membrane phospholipids.

Econazole nitrate is a broad spectrum antimycotic with activity against dermatophytes, yeasts and moulds. A clinically relevant action against Gram positive bacteria has also been found.

Econazole nitrate has no anti-inflammatory action, no effect on circulation, no central or autonomic nervous effects, no effects on respiration, no effect on α or β receptors, no anticholinergic or antiserotonergic reactions.

Econazole nitrate is only slightly absorbed from the vagina and skin. No active drug has been detected in the serum. Radio labelling shows that less than 0.1% of an oral dose is absorbed. Peak serum levels are achieved after 2 hours and 90% binds to plasma proteins. Metabolism is limited but occurs primarily in the liver with excretion of metabolites in the urine.

Low neonatal survival and foetal toxicity was associated with high doses. In animal studies, econazole nitrate has shown no teratogenic effects but was foetotoxic in rodents at maternal subcutaneous doses of 20 mg/kg/day and at maternal oral doses of 10 mg/kg/day. The significance of this in humans is unknown. In repeat dose toxicity studies in rats, at high subcutaneous doses (50 mg/kg/day, 300 mg/m²/day) the liver was identified as a target organ with minimal toxicity and full recovery. The human to animal safety margin for liver toxicity (based on Human Equivalent Dose taking into account normalisation of body surface area) is 32 to 126x for a 50 to 70 kg human based on 2.5 to 7% absorption in humans and 83% bioavailability in rats. No significant topical toxicity, phototoxicity, local dermal irritation, vaginal irritation or sensitization was noted. Only mild ocular irritation was noted with a cream formulation.

Following oral administration of econazole nitrate to lactating rats, econazole and/or metabolites were excreted in milk and were found in nursing pups.