Clotrimazole (Canestan, Bayer; and multiple other names) is a synthetic imidazole. It was first used in patients in the late 1970’s and licensed for use in before 1982. It gained OTC (over the counter) status in 1989 in the USA. Its patents, some with formulations, starting expiring in the early 1990’s. It inhibits the production of ergosterol, a central chemical in the cell membranes of fungi, by interfering with 14 alpha demethylase.
Dose & Delivery
Clotrimazole is only used topically and is formulated alone or with other active ingredients such as corticosteroids. Most topical skin preparations are 1% cream, lotion or spray, which should be applied 2 or 3 times daily for 2-4 weeks. Clotrimazole is effective for seborrheic dermatitis, nappy rash due to Candida, some cases of ringworm, tinea cruris and athlete’s foot. A 1% solution can be used for otitis externa. For inflammatory conditions such as seborrheic dermatitis, combined preparations with topical corticosteroid are helpful.
For vaginal candidiasis, pessaries of 100mg are give daily for 6 days, 200mg for 3 days and 500mg as a single dose. Alternatively 1%, 2% or 10% vaginal cream delivering roughly the same doses as pessaries, may be used, for the same durations. Clotrimazole cream is also used to treat penile candidiasis (balanitis).
Clotrimazole 10mg lozenges or troches are used to treat oral candidiasis. They are taken 5 times daily for 14 days for treatment, or 3 times daily for prevention of oral candidiasis.
Fungi - the drug is active against
Clotrimazole is active against most Candida species and skin fungi such as Trichophyton spp., Microsporum spp. and Epidermophyton floccosum and Malassezia spp. In vitro it also has activity against many fungi generally susceptible to azoles such as Coccidioides immitis, but as it cannot be given systemically, this is of limited importance.
Some clotrimazole resistance is documented in Candida albicans, especially among oral isolates in patients with AIDS treated with Clotrimazole. Typical rates of resistance, in Candida albicans in a general hospital are 3-6%.
Metabolism and distribution
Clotrimazole is practically insoluble in water. Applied on the skin it penetrates on the surface layer (epidermis), with no systemic absorption. Between 3-10% is absorbed systemically after vaginal administration. Clotrimazole is metabolised by the liver.
Drug/ Drug interactions
There are very few drug/drug interactions with clotrimazole. Pessaries of clotrimazole may damage latex condoms or diaphragms, and additional contraceptive measures are wise. View drug interactions database.
Clotrimazole is generally well tolerated but nausea, vomiting, unpleasant mouth and pruritus (itching) have been reported with oral lozenges. Local skin irritation and a burning sensation are reported after use on the skin. Clotrimazole may be given in pregnancy, although nystatin is preferred..
Structure of clotrimazole