MICONAZOLE NITRATE
Clinical safety rating: safe
Human studies have proved safety
Inhibits fungal CYP450 14α-demethylase, blocking ergosterol synthesis and disrupting fungal cell membrane integrity.
| Metabolism | Hepatic metabolism via CYP450 enzymes (primarily CYP3A4) to inactive metabolites. |
| Excretion | Miconazole is primarily metabolized in the liver, with less than 1% of an intravenous dose excreted unchanged in urine. Biliary/fecal elimination accounts for approximately 50% of the dose as metabolites. Renal elimination of metabolites is minimal. |
| Half-life | Terminal elimination half-life is approximately 24 hours (range 20-40 hours) following intravenous administration. This extended half-life supports twice-daily dosing for systemic infections. |
| Protein binding | Approximately 91-93% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution is approximately 20-23 L/kg, indicating extensive tissue penetration and sequestration. |
| Bioavailability | Oral: negligible (<1%) due to poor absorption; intravaginal: approximately 10-15% systemic absorption; topical: minimal systemic absorption (approximately 1-2%). |
| Onset of Action | Intravenous: immediate onset; topical: antifungal effect begins within 24-48 hours; intravaginal: symptomatic relief often within 24-72 hours. |
| Duration of Action | Intravenous: dosing intervals are 12 hours due to half-life; topical: effects persist for days after discontinuation due to skin retention; intravaginal: single dose provides therapeutic levels for 3-5 days. |
Topical: Apply twice daily for 2-4 weeks. Vaginal: 200 mg suppository at bedtime for 3 days, or 100 mg suppository at bedtime for 7 days, or 1200 mg suppository as a single dose. Oral (buccal): 50 mg once daily for 14 days.
| Dosage form | CREAM |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. For severe renal impairment (CrCl < 30 mL/min), consider dose reduction or increased interval; safety data limited. |
| Liver impairment | No specific adjustment for Child-Pugh A or B. For Child-Pugh C, use with caution; systemic absorption may increase, monitor for adverse effects. |
| Pediatric use | Topical: Apply twice daily for 2-4 weeks (all ages). Vaginal: Not recommended for prepubertal girls. Oral buccal: Not recommended for children < 16 years. |
| Geriatric use | No specific adjustment needed for topical or vaginal use. For oral buccal, no dose adjustment required; monitor for adverse effects due to potential age-related decline in renal/hepatic function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Warfarin metabolism is inhibited increasing INR For topical use only not for ophthalmic use.
| Breastfeeding | Miconazole nitrate is likely excreted into breast milk in small amounts due to low molecular weight and lipid solubility, but the M/P ratio has not been established. Systemic absorption from topical/vaginal use is minimal (<1.4%), making infant exposure negligible. The American Academy of Pediatrics considers miconazole compatible with breastfeeding when used topically/vaginally. |
| Teratogenic Risk | Miconazole nitrate is classified as FDA Pregnancy Category C. In the first trimester, there is a potential risk based on animal studies showing embryotoxicity and increased resorptions at high oral doses. However, extensive clinical experience with topical and intravaginal formulations in pregnant women has not demonstrated an increased risk of major birth defects or miscarriage. Second and third trimester use is considered safe with topical/vaginal administration; systemic absorption is minimal. |
■ FDA Black Box Warning
None.
| Common Effects | vaginal yeast infections |
| Serious Effects |
Hypersensitivity to miconazole or any component; concomitant use with ergot alkaloids, oral midazolam, triazolam, HMG-CoA reductase inhibitors (e.g., simvastatin, lovastatin), pimozide, quinidine, and CYP3A4 substrates with narrow therapeutic index.
| Precautions | Hepatic impairment; avoid oral use in patients with hepatic disease; limit systemic absorption; possible hypersensitivity reactions; use during pregnancy only if clearly needed. |
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| Fetal Monitoring | No specific maternal or fetal monitoring is required for topical or vaginal miconazole use during pregnancy. For oral or IV use (rare), monitor liver function tests, renal function, and signs of fetal distress. Standard prenatal care should be maintained. |
| Fertility Effects | Miconazole has been shown to inhibit spermatogenesis in animal models at high systemic doses. In humans, no adverse effects on female fertility have been reported with topical or vaginal use. Systemic absorption is minimal, making significant reproductive toxicity unlikely. |