Ciclopirox: recent nonclinical and clinical data relevant to its use as a topical antimycotic agent

Ciclopirox is a topical antimycotic agent belonging to the chemical class of hydroxypyridones and not related to azoles or any other class of antifungal agents. Its antimicrobial profile includes nearly all of the clinically relevant dermatophytes, yeasts and moulds, and is therefore broader than that of most other antimycotics. It is also active against certain frequently azole-resistant Candida species and against some bacteria. The mechanism of action of ciclopirox is different from that of other topical antifungal drugs, which generally act through ergosterol inhibition. The high affinity of ciclopirox for trivalent metal cations, resulting in inhibition of the metal-dependent enzymes that are responsible for the degradation of peroxides within the fungal cell, appears to be the major determinant of its antimicrobial activity. This unique and multilevel mechanism of action provides a very low potential for the development of resistance in pathogenic fungi, with cases of resistance rarely reported. Ciclopirox also displays mild anti-inflammatory effects in biochemical and pharmacological models; effects also shown in small clinical studies. Scavenging of reactive oxygen species released from inflammatory cells is a likely contributor to these anti-inflammatory effects. Ciclopirox, and its olamine salt, is available in multiple topical formulations, suitable for administration onto the skin and nails and into the vagina. The pharmaceutical forms most widely investigated are 1% ciclopirox olamine cream and 8% ciclopirox acid nail lacquer, but lotion, spray, shampoo, pessary, solution, gel and douche formulations have also been used. Ciclopirox penetrates into the deep layers of the skin, mucosal membranes and nail keratin, reaching concentrations exceeding the minimal fungicidal concentrations for most medically important fungi. A large number of clinical trials were and are still being performed with ciclopirox, starting in the early 1980s. Ciclopirox was first developed for fungal skin infections and vaginal candidiasis, and is currently well established in these indications. More recently, the drug has been clinically investigated in seborrhoeic dermatitis and onychomycosis, showing good efficacy and excellent tolerability. Emphasis in this review is given to a ciclopirox medicated nail lacquer, which is based on an original technology and has superior properties in terms of its affinity to keratin and nail permeation. It has been found to have superior efficacy and safety to another commercially available formulation in the treatment of onychomycosis. The safety features of ciclopirox are well known. The topical drug is devoid of systemic adverse reactions. Mild local reactions characterized by a burning sensation of the skin, irritation, redness, pain or pruritus, generally in less than 5% of treated patients, can be observed following skin and vaginal application. With nail application, the most common adverse event is the appearance of mild erythema in 5% of the treated population. As a general conclusion, although less effective than some oral antimycotic agents in various indications, ciclopirox compares very well in terms of the benefit/risk ratio due to its excellent tolerability and complete absence of serious adverse effects.