CLOTRIMAZOLE
Clinical safety rating: safe
No significant drug interactions For topical use only not for ophthalmic use.
Clotrimazole inhibits fungal cytochrome P450 14α-demethylase, disrupting ergosterol biosynthesis and increasing membrane permeability.
| Metabolism | Hepatic metabolism via cytochrome P450 enzymes (CYP3A4) to inactive metabolites. |
| Excretion | Primarily fecal (biliary) as unchanged drug and metabolites; minimal renal excretion (<1% unchanged). |
| Half-life | Terminal half-life is approximately 3-6 hours; due to rapid hepatic metabolism and extensive tissue distribution, clinical effects persist longer than plasma levels suggest. |
| Protein binding | 90% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Approximately 15 L/kg, indicating extensive tissue penetration and accumulation in skin, vagina, and mucosa. |
| Bioavailability | Oral: negligible (<1% systemic absorption); topical/vaginal: minimal absorption (<0.5%); lozenges: local delivery only. |
| Onset of Action | Topical: pruritus relief within 24-48 hours; vaginal: symptoms improve within 1-3 days; oral lozenges: not applicable for systemic effects. |
| Duration of Action | Topical: clinical cure typically within 1-2 weeks; vaginal: single dose provides therapeutic levels for 3-7 days; oral lozenges: local effect persists as long as lozenge is in mouth. |
| Molecular Weight | 344.84 |
Topical: Apply thin layer to affected area twice daily for 2-4 weeks. Oral troche: 10 mg troche dissolved slowly in mouth 5 times daily for 14 days. Vaginal: One 100 mg suppository intravaginally at bedtime for 7 days, or 200 mg suppository for 3 days, or 500 mg single dose.
| Dosage form | CREAM |
| Renal impairment | No dose adjustment required for any route; systemic absorption is minimal with topical and vaginal use. For oral troche, caution in severe renal impairment due to limited data. |
| Liver impairment | No dose adjustment required for topical or vaginal routes. For oral troche, caution in severe hepatic impairment (Child-Pugh C) due to potential accumulation; consider alternative therapy. |
| Pediatric use | Topical: Apply twice daily for 2-4 weeks; safe for all ages. Oral troche: Not recommended for children under 3 years due to risk of choking. Vaginal: Not indicated for prepubertal girls. |
| Geriatric use | No dose adjustment required for topical, vaginal, or oral troche. Ensure proper administration of troche to prevent aspiration. Monitor for adverse effects in frail elderly with prolonged use. |
| 1st trimester | Topical clotrimazole is generally considered safe during the first trimester. Systemic absorption is minimal (<1%), and animal studies show no teratogenicity. However, use only if clearly needed. |
| 2nd trimester | Safe for topical use. Systemic absorption negligible; no known fetal risk. |
| 3rd trimester | Safe for topical use. Vaginal formulations may be used near term; theoretical risk of uterine contractions with intravaginal application is minimal. |
Clinical note
No significant drug interactions For topical use only not for ophthalmic use.
| FDA category | Human |
| Placental transfer | Minimal. Systemic absorption after topical application is <1%, leading to negligible placental transfer. No specific studies, but low plasma levels suggest insignificant transfer. |
■ FDA Black Box Warning
None.
| Common Effects | vaginal yeast infections |
| Serious Effects |
Known hypersensitivity to clotrimazole or any component of the formulation
| Precautions | Hepatic impairment (caution if systemic absorption), avoid occlusive dressings over large areas, topical use only (not for systemic fungal infections), discontinue if irritation or sensitization occurs. |
| Food/Dietary | No significant food interactions for topical clotrimazole. For oral lozenges, no dietary restrictions. |
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| Breastfeeding |
| Topical clotrimazole is poorly absorbed systemically. Use on skin or vagina is unlikely to result in significant infant exposure. It is considered compatible with breastfeeding. Avoid application to breast area to prevent infant ingestion. |
| Lactation Rating | L2 (Probably compatible) |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of fetal harm in animal studies; however, adequate human studies in pregnant women are lacking. Topical use with minimal systemic absorption is considered low risk. No known association with major malformations. Trimester-specific risks: Not reported. |
| Fetal Monitoring | No specific monitoring required for topical use. For systemic use (not recommended in pregnancy), monitor liver function tests due to potential hepatotoxicity. |
| Fertility Effects | No known effect on fertility in animal studies. Human data are lacking. |
| Clinical Pearls | Clotrimazole is a broad-spectrum azole antifungal used topically for dermatophyte and Candida infections. Avoid contact with eyes. For vaginal candidiasis, a single 500 mg vaginal tablet or 100 mg nightly for 7 days is effective. Do not use occlusive dressings unless directed. Resistance is rare but seen with prolonged use. |
| Patient Advice | Apply to clean, dry skin and rub in gently. · Use for the full treatment duration even if symptoms improve. · Avoid tight-fitting clothing or synthetic fabrics that trap moisture. · Do not use on open wounds or broken skin. · If using for vaginal infection, complete the full course and avoid intercourse during treatment. · Wash hands before and after application. |