FEMSTAT
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FEMSTAT (FEMSTAT).
FEMSTAT (butoconazole) is an imidazole antifungal agent that inhibits fungal cytochrome P450 14α-demethylase, thereby blocking the conversion of lanosterol to ergosterol, a key component of the fungal cell membrane. This disrupts membrane integrity and function, leading to fungal cell death.
| Metabolism | Butoconazole is primarily metabolized in the liver via oxidation and glucuronidation; specific CYP enzymes have not been fully elucidated. |
| Excretion | Primarily hepatic metabolism; <10% excreted unchanged in urine. Fecal excretion accounts for approximately 30% of metabolites. |
| Half-life | Terminal half-life: 6-9 hours; clinical context: supports twice-daily dosing for consistent therapeutic levels. |
| Protein binding | Bound: 95-98%; binding proteins: primarily albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd: 0.35-0.45 L/kg; indicates distribution primarily into extracellular fluid with moderate tissue binding. |
| Bioavailability | Intravaginal: absorption is limited and variable, with systemic bioavailability estimated at 5-10%; not administered orally. |
| Onset of Action | Intravaginal: clinical relief typically begins within 1-2 hours after application. |
| Duration of Action | Duration: 12-24 hours; clinical note: symptomatic relief persists for the dosing interval with twice-daily administration. |
Butoconazole nitrate 2% vaginal cream: one applicatorful (approximately 5 g) intravaginally at bedtime for 3 days. Alternatively, butoconazole nitrate 2% single-dose vaginal cream: one applicatorful (approximately 5 g) intravaginally as a single dose.
| Dosage form | CREAM |
| Renal impairment | No dosage adjustment required for renal impairment; renal clearance is not a significant elimination pathway. |
| Liver impairment | No dosage adjustment required for hepatic impairment; hepatic metabolism is minimal. |
| Pediatric use | Safety and efficacy in pediatric patients have not been established; use only if clearly needed. |
| Geriatric use | No specific dosage adjustment required; use standard adult dosing. Limited data in elderly, but no age-related pharmacokinetic differences expected. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FEMSTAT (FEMSTAT).
| Breastfeeding | Butoconazole is poorly absorbed into systemic circulation after vaginal use, and excretion into breast milk is likely negligible. No specific studies report M/P ratio; however, based on low plasma levels, the estimated infant dose is <1% of maternal vaginal dose. The drug is compatible with breastfeeding. Caution is advised in nursing mothers of low-birth-weight or premature infants, but no adverse effects have been reported. |
| Teratogenic Risk | FEMSTAT (butoconazole nitrate) is an azole antifungal used intravaginally. Systemic absorption is minimal (approximately 1.7%) following vaginal administration. Available data from case reports and small studies do not suggest an increased risk of major birth defects or miscarriage. No teratogenic effects were observed in animal reproduction studies at doses up to 5 mg/kg/day (systemic exposure). First trimester exposure: limited data, no signal for teratogenicity. Second and third trimesters: no known fetal risks; considered safe for use. Overall, classified as FDA Pregnancy Category C due to lack of well-controlled human studies, but risk is considered low given minimal absorption. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hypersensitivity to butoconazole or any component of the formulation."]
| Precautions | ["For intravaginal use only; not for ophthalmic or oral use.","Discontinue if sensitization or irritation occurs.","Use during pregnancy only if clearly needed; may increase risk of fetal harm in first trimester.","Patients with diabetes or HIV may be at higher risk for recurrent infections."] |
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| Fetal Monitoring | No specific maternal or fetal monitoring required beyond routine prenatal care. In case of prolonged use or signs of systemic toxicity (e.g., skin irritation, burning), assess for allergic reaction. No fetal monitoring indicated. |
| Fertility Effects | No adverse effects on fertility reported in animal studies at systemic exposures up to 5 mg/kg/day. In humans, no studies have evaluated fertility; however, due to minimal systemic absorption, a significant impact on fertility is unlikely. |