Miconazol

Because of their limited, activity, small spectmm, and side effects, the older topical antimycotics have generally been surpassed by newer antimycotic chemotherapeutic agents. These newer antimycotics for topical use iaclude the imida2ole derivatives clotrimazole, miconazole, econazole, isoconazole, sulconazole, fenticonazole, oxiconazole, bifonazole, butoconazole, ziaoconazole, tioconazole, and the triazole derivative, terconazole (Table 2) (5—7). The iatroduction of the azole derivatives represents a milestone ia the treatment of mycoses. 

Miconazole. Miconazole nitrate [22832-87-7] (Fig. 2), the 1-phenethyl-imidazole derivative first described in 1969, interferes at low doses with the cytochrome P-450 dependent ergosterol biosynthesis in yeasts and fungi. The result is accumulation of C-14 methylated sterols on the one hand and reduction of the ergosterol levels in the membranes on the other hand (12). Analogous to clotrimazole, this leads to a disturbance in the membranes it results in inhibition of ceU repHcation, mycelium development (in C. albicans) and finally, ceU death. High concentrations of miconazole, which may be achieved with topical use, disturb the orientation of phosphoHpids in the membranes, which produces leaks (13). 

Miconazole. Miconazole (Fig. 2, 7a) is also available as a sterile solution for intravenous infusion. Miconazole has a therapeutic effect on systemic mycoses due to C albicans A.spergillusfumigatus Cyptococcus neoformans Blastomyces dermatitidis Histoplasma capsulatum Coccidioides immitis Paracoccidioides brasiliensis and Petriellidum boydii. 

Ketoconazole. For treatment of systemic mycoses with amphotericin B or miconazole, the patient must be admitted to a hospital. This is not always possible, particularly in areas where systemic mycoses occur frequently, nor is it always desirable, because of the expense. For these reasons, it was desirable to find an antimycotic that combined safety and broad-spectmm activity with oral adraiinistration. Ketoconazole (10), which is orally active, met most of these requirements. This inhibitor of the ergosterol biosynthesis is an A/-substituted imidazole, that differs from its precursors by the presence of a dioxolane ring (6,7). Ketoconazole is rapidly absorbed in the digestive system after oral adrninistration. Sufficient gastric acid is required to dissolve the compound and for absorption. Therefore, medication that affects gastric acidity (for example, cimetidine and antacids) should not be combined with ketoconazole. 

Plasma levels of 3—5 p.g/mL are obtained two hours after adraiinistration of 200 mg ketoconazole. No accumulation in the bloodstream was noted after a 30-wk treatment with this dose. The half-life is approximately eight hours. When ketoconazole is taken with meals, higher plasma levels are obtained. Distribution studies using radioactive ketoconazole in rats show radioactivity mainly in the Hver and the connective tissue. Radioactivity is also present in the subcutaneous tissue and the sebaceous glands. After one dose of 200 mg in humans, ketoconazole is found in urine, saUva, sebum, and cenimen. Like miconazole, the mode of action is based on inhibition of the cytochrome P-450 dependent biosynthesis of ergosterol. This results in disturbed membrane permeabiUty and membrane-bound enzymes (8,10,23,25). 

A combination of amphotericin B, miconazole (16), and rifampin (17) was used to successfully cure one patient. In addition, tetracycline (7) and minocycline (18) have been recommended although their clinical efficacy have not been estabUshed. No proven therapeutic agents exist for treating A.catbamoeba infections, however, the phenothiazines, trifluoperazine [117-89-5] and chlorpromazine [50-53-3], show promise in vitro. 

Imidazole antimycotics, ketoconazole, clotrimazole, and miconazole are potent inhibitors of various cytochrome P450-isoenzymes that also affect the metabolism of retinoids. They were fust shown to inhibit the metabolism of RA in F9 embryonal carcinoma cells. When tested in vitm liarazole, a potent CYP-inhibitor, suppressed neoplastic transformation and upregulated gap junctional communication in murine and human fibroblasts, which appeared to be due to the presence of retinoids in the serum component of the cell culture medium. Furthermore, liarazole magnified the cancer chemopreventive activity of RA and (3-carotene in these experiments by inhibiting RA-catabolism as demonstrated by absence of a decrease in RA-levels in the culture medium in the presence of liarazole over 48 h, whereas without liarazole 99% of RA was catabolized. In vivo, treatment with liarazole and ketoconazole reduced the accelerated catabolism of retinoids and increased the mean plasma all-irans-RA-concentration in patients with acute promyelocytic leukemia and other cancels. 

Administration of miconazole for a vulvovaginal fungal infection may cause irritation, sensitization, or vulvo-vaginal burning. Skin irritation may result in redness, itching, burning, or skin fissures. Other adverse reactions with miconazole include cramping, nausea, and headache Adverse reactions associated with topical use are usually not severe. 

Miconazole If the drug (cream or tablet) is administered vaginally, insert the drug high in the vagina using tiie applicator provided with the product. 

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