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...

Superficial mycoses caused by Trichophyton rubrum are among the most common infections worldwide. T. rubrum infections are difficult to treat and are often associated with recurrences after interruption of the antifungal therapy. Nevertheless, reports on T. rubrum resistance to commonly used antifungal drugs are rare. In this study, we compared the in vitro resistance frequencies and development of resistance to terbinafine, itraconazole, amorolfine, and ciclopirox in T. rubrum. Results demonstrated that naturally occurring mutants were isolated at a frequency of 10 ؊7 for itraconazole and 10 ؊9 for terbinafine and amorolfine. To mimic conditions of body sites in which low drug levels are reached during therapy, T. rubrum was propagated for 10 transfers in media containing subinhibitory drug concentrations. Resistance to itraconazole, terbinafine, and amorolfine emerged at a higher frequency than was seen with spontaneous mutation. Itraconazole-resistant mutants also showed decreased susceptibility to amorolfine as well as to terbinafine, and amorolfine-resistant mutants were also less susceptible to terbinafine. No mutant resistant to ciclopirox was isolated, suggesting no propensity of T. rubrum to develop resistance to this drug. How different drug mechanisms of action can influence the onset of resistance is discussed.

Commercial antimycotic nail lacquers are commonly based on water-insoluble resins. The present study was aimed at evaluating a novel, experimental nail lacquer (P-3051, Polichem SA, Lugano, Switzerland) based on the water-soluble film-forming agent hydroxypropyl chitosan (HPCH). The in vitro permeation of ciclopirox (CPX) from P-3051 and from a commercial, water-insoluble lacquer based on a vinyl resin (Penlac, Aventis Pharma), was investigated using thin membranes obtained from bovine hooves, an accepted model for human nails. Similar CPX permeation fluxes at steady state through the membranes, but significantly different lag times were observed for P-3051 and Penlac, when these were tested as dry films. The formulations thus appeared to influence only the time required by CPX to saturate the membrane, and not the final drug concentration gradient in the membrane. Permeation experiments performed on the same membranes and on hairless mouse skin with P-3051 and with a similar, HPCH-free vehicle (ERV), both tested in liquid form, disproved the possibility that HPCH might act as a permeation enhancer for CPX in either substrate. The possible reasons for the greater efficiency of the HPCH vehicle in terms of CPX transfer from the vehicle itself to the keratin membrane are discussed. This effect might be tentatively attributed to a particular affinity of HPCH for the membrane, resulting in intimate contact and strong adhesion of the HPCH lacquer to the keratin substrate.

To compare transungual permeation of CPX with that of MRF in the same hydroxypropyl chitosan-based nail lacquer (MRF/sol) and with a nonwater-soluble reference (Loceryl); Galderma International, La Défense, France), and to evaluate the antimycotic activity of CPX/sol and Loceryl against the most common fungal strains that cause onychomycosis. Methods In vitro drug permeation experiments with CPX/sol, MRF/sol and Loceryl were carried out through bovine hoof slices. Experimental permeates from CPX/sol and Loceryl underwent in vitro susceptibility testing against clinical isolates of dermatophytes, moulds and yeast. Results MRF transungual flux from MRF/sol lacquer was significantly higher when compared with Loceryl. CPX was able to permeate hoof membranes more easily compared with MRF. CPX and MRF concentrations in the subungual fluids collected after application of CPX/sol or Loceryl were sufficient to inhibit fungal growth, with the exception of Candida parapsilosis. Smaller amounts of fluid containing CPX were required for complete inhibition of fungal growth. Efficacy index values were significantly higher for CPX/sol. Conclusions Application of the CPX/sol nail lacquer allows rapid nail penetration of CPX, providing CPX levels sufficient to inhibit fungal growth for a prolonged period of time (30 h) after application of lacquer dose. CPX/sol nail lacquer appeared superior to the market reference Loceryl in terms of both vehicle (hydroxypropyl chitosan) and active ingredient (CPX) as witnessed by its higher efficacy on all nail pathogens.

This study confirms the validity of bovine hoof slices as a model for infected human nails, and suggests a substantial equivalence between the two models. Following P-3051 application, CPX reaches fungicidal concentrations in and through human infected toenails.