Miconazole microbiology
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ahmed Zaghw, M.D. [2]
Microbiology
Mechanism of Action
Miconazole inhibits the enzyme cytochrome P450 14α-demethylase which leads to inhibition of ergosterol synthesis, an essential component of the fungal cell membrane. Miconazole also affects the synthesis of triglycerides and fatty acids and inhibits oxidative and peroxidative enzymes, increasing the amount of reactive oxygen species within the cell.
Activity in vitro and in vivo
Miconazole is active against Candida albicans, C. parapsilosis, and C. tropicalis. Correlation between minimum inhibitory concentration (MIC) results in vitro and clinical outcome has yet to be established.
Drug Resistance
In vitro studies have shown that some Candida strains that demonstrate reduced susceptibility to one antifungal azole may also exhibit reduced susceptibility to other azoles suggesting cross-resistance.
Clinically relevant resistance to systemically utilized triazoles may occur in Candida species. Resistance may occur by multiple mechanisms such as changes in amino acids and/or in the regulation of the target enzyme and of a variety of efflux pump proteins. Multiple mechanisms may co-exist in the same isolate. Resistance breakpoints, correlating in vitroactivity with clinical efficacy, have not been established for miconazole.
Clinical Studies
Study in HIV Infected Patients
The efficacy and safety of ORAVIG in the treatment of OPC was evaluated in a randomized, double-blind, double-dummy, multicenter trial comparing ORAVIG 50 mg once daily for 14 consecutive days (n = 290) with clotrimazole troches 10 mg 5 times per day for 14 days (n = 287) in HIV-positive patients with OPC. Seventy-five percent of patients were not receiving highly active antiretroviral treatment, 5% had CD4+ cell count < 50 cells/mm 3, and 17% had a history of previous OPC. The mean viral load was 117,000 copies/mL. Patients were required to have symptoms and microbiological documentation of OPC for study entry. Most of the infections were caused by C. albicans (85%), followed by C. tropicalis (9%), and C. parapsilosis (3%). About 2% of the subjects were infected with more than one Candidaspecies.
Clinical cure [defined as a complete resolution of both signs and symptoms of OPC at the test of cure (TOC) visit (days 17-22)], and clinical relapse by days 35-38 (21-24 days after end of therapy) are presented in Table 5. Mycological cure [defined as eradication (i.e., no yeast isolates) of Candida species] at the TOC visit (days 17-22) is also reported in the table.
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Study in Head and Neck Cancer Patients
The efficacy and safety of ORAVIG 50 mg was evaluated in an open-label, randomized, multicenter trial comparing ORAVIG 50 mg once daily for 14 days to miconazole oral gel 125 mg four times daily for 14 days in head and neck cancer patients who had received radiation therapy. Most of the infections were caused by C. albicans (71%), andC. tropicalis (8%). About 7% of the subjects were infected with more than one Candida species. Success rates of treatment at day 14 [defined as a complete (complete disappearance of candidiasis lesions) or partial response (improvement by at least 2 points of the score for extent of oral lesion compared with the score at day 1) based on a blind assessment] are shown in Table 6. Also reported in Table 6 are relapse rate at day 30, and mycologic cure assessed at day 14.[1]
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References
Adapted from the FDA Package Insert.