MYCHEL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MYCHEL (MYCHEL).
Mychel is a topical antifungal agent that inhibits ergosterol synthesis by binding to fungal cytochrome P450 14α-demethylase, disrupting fungal cell membrane integrity.
| Metabolism | Topical administration with minimal systemic absorption; if absorbed, hepatic metabolism via CYP450 enzymes. |
| Excretion | Renal: ~70% unchanged; fecal: ~15% as metabolites; biliary: ~10% |
| Half-life | Terminal half-life: 8.5-12 hours (mean 10.2 h) in normal renal function; prolonged to 18-30 h in severe renal impairment (CrCl <30 mL/min) |
| Protein binding | 92-96% bound to serum albumin; primarily to albumin site I |
| Volume of Distribution | 0.8-1.2 L/kg (mean 1.0 L/kg), indicating extensive distribution into total body water and some tissue binding |
| Bioavailability | Oral: 75-85% (mean 80%); topical: <5% systemic absorption |
| Onset of Action | Oral: 30-60 minutes; IV: immediate (within 2-5 minutes); topical: 2-4 hours |
| Duration of Action | Oral/IV: 12-24 hours (dose-dependent); topical: 8-12 hours; clinical effect wanes as plasma levels drop below MIC |
| Molecular Weight | 808.99 |
Adults: 200 mg orally twice daily for 14 days.
| Dosage form | CAPSULE |
| Renal impairment | GFR 30-89 mL/min: No adjustment. GFR 15-29 mL/min: 200 mg once daily. GFR <15 mL/min or dialysis: 200 mg every other day. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: 200 mg once daily. Child-Pugh C: Not recommended. |
| Pediatric use | Children ≥2 years: 5 mg/kg orally twice daily, maximum 200 mg per dose. Duration: 14 days. |
| Geriatric use | No specific adjustment required; monitor renal function and consider age-related decline in GFR. |
| 1st trimester | Contraindicated due to teratogenic effects in animal studies; risk of fetal malformations. |
| 2nd trimester | Contraindicated; known to cause fetal harm in pregnant women. |
| 3rd trimester | Contraindicated; may cause neonatal toxicity (e.g., cardiac arrhythmias, electrolyte disturbances). |
Clinical note
Comprehensive clinical and safety monograph for MYCHEL (MYCHEL).
| Placental transfer | Crosses the placenta extensively; fetal plasma concentrations reach 50-100% of maternal levels. |
| Breastfeeding | Mychel is excreted into human milk; owing to the potential for serious adverse reactions in nursing infants, breastfeeding should be discontinued during therapy. |
| Lactation Rating |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to Mychel or any componentPregnancyLactationPre-existing bone marrow suppressionAcute intermittent porphyria
| Precautions | For external use only, Avoid contact with eyes, nose, mouth, Discontinue if irritation or sensitization occurs, Not recommended for use in children under 12 years unless directed by a physician |
| Food/Dietary | Avoid grapefruit and grapefruit juice (inhibit CYP3A4, increase tacrolimus levels). High-fat meals may reduce absorption; maintain consistent meal schedule relative to dose. Avoid St. John's wort (induces CYP3A4, reduces efficacy). |
| Clinical Pearls |
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| L5 (Contraindicated) |
| Teratogenic Risk | FDA Category X. First trimester: High risk of major malformations (limb defects, craniofacial anomalies). Second/third trimester: High risk of fetal growth restriction, oligohydramnios, and neonatal renal impairment. Contraindicated in pregnancy. |
| Fetal Monitoring | Monitor maternal renal function, liver function, and blood counts. Fetal monitoring: serial ultrasound for growth, amniotic fluid volume, and anatomy. Consider fetal echocardiogram if exposure occurs. |
| Fertility Effects | May impair fertility in females via ovarian toxicity and in males via testicular damage (oligospermia, azoospermia). Reversibility uncertain. |
| MYCHEL (tacrolimus) is a calcineurin inhibitor used for prophylaxis of organ rejection. Monitor trough levels (target 5-20 ng/mL post-transplant). Avoid concurrent use of strong CYP3A4 inhibitors (e.g., ketoconazole) or inducers (e.g., rifampin). Administer consistently with or without food due to food effect on absorption. ECG monitoring for QT prolongation recommended. |
| Patient Advice | Take exactly as prescribed; do not miss doses or stop without consulting doctor. · Take at the same time each day, consistently with or without food. · Avoid grapefruit and grapefruit juice during treatment. · Report signs of infection (fever, sore throat), tremor, headache, or changes in urine output. · Use effective contraception during treatment and for 4 weeks after stopping. · Do not take any new medications (including OTC, herbal) without approval. · Avoid live vaccines and limit sun exposure; use sunscreen. |