Pharmacodynamics: Miconazole possesses an antifungal activity against the common dermatophytes and yeasts as well as an antibacterial activity against certain gram-positive bacilli and cocci. Its activity is based on the inhibition of a demethylation step in the ergosterol biosynthesis. Ergosterol, the end-product of the biosynthetic pathway and the main sterol in yeast and fungi. The disruption in production of ergosterol disrupts the fungal cell membrane, causing holes to appear in it. These holes allow the essential constituents of the fungal cells to leak out and ultimately the fungal cells die.
Pharmacokinetics: The oral bioavailability of Miconazole is low (25-30%) because there is little absorption of Miconazole from the intestinal tract. Miconazole is systemically absorbed after administration as the oral gel. Absorbed Miconazole is bound to plasma proteins (88.2%), primarily to serum albumin and red blood cells (10.6%). The absorbed portion of Miconazole oral gel is largely metabolized; less than 1% of the administered dose is excreted unchanged in the urine. The terminal plasma half-life is 20-25 hours in most patients. The elimination half-life of Miconazole is similar in any renal impaired patient.
Concomitant treatment with Terfenadine, Astemizole and Cisapride should be avoided because in vitro studies suggest that Miconazole may inhibit their metabolism, so these products miqht precipitated.
Miconazole may delay Phenytoin and Cyclosporine metabolism and this might precipitate Phenytoin and Cyclosporine toxicity, respectively.
Miconazole is contraindicated in patients with known hypersensitivity to the active ingredient.
Occasionally nausea and vomiting, diarrhea with long term use and rarely allergic reactions.
There is no information regarding the safety of Miconazole oral gel during pregnancy. So Miconazole oral gel should be avoided in pregnant women if possible or the potential hazards should be balanced against the possible benefits. As many drugs are excreted in human milk, caution should be exercised when Miconazole is administered to a nursing woman.
If the concomitant use of Miconazole and anticoagulant is considered, the anti-coagulant effect should be monitored and titrated. Miconazole and phenytoin plasma level should also be monitored when used concomitantly. In infants and young children, caution must be taken to ensure that the gel does not obstruct the throat.
