GRISACTIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for GRISACTIN (GRISACTIN).
Binds to microtubules and disrupts mitotic spindle formation, inhibiting fungal cell division.
| Metabolism | Hepatic metabolism via N-demethylation and glucuronidation; primarily metabolized by CYP450 enzymes. |
| Excretion | Renal: <1% as intact drug; fecal: >99% as metabolites (mainly 6-demethylgriseofulvin glucuronide) via bile; negligible biliary excretion of parent compound. |
| Half-life | Terminal elimination half-life: 9–24 hours (mean ~14 hours). Clinical context: Steady-state achieved in 3–5 days; once-daily dosing is effective due to prolonged half-life. |
| Protein binding | Extensively bound to plasma proteins (>97%), primarily to albumin and possibly other proteins. |
| Volume of Distribution | Apparent Vd: 0.25–0.58 L/kg. Indicates distribution into total body water and deep tissue compartments (e.g., skin, hair, nails, liver, fat). Accumulates in keratin precursor cells. |
| Bioavailability | Oral bioavailability is variable (approximately 50% for micronized formulation; ultra-microsized formulation ~100% relative to micronized). GRISACTIN is micronized; absorption enhanced by fatty meal. |
| Onset of Action | Oral: For tinea capitis, clinical improvement seen in 1–2 weeks; for nail infections, requires months. Peak plasma concentrations at 4–6 hours post-dose. |
| Duration of Action | Therapeutic effect persists as long as drug is present in keratin (stratum corneum, hair, nails). Duration of action: Therapy must continue until infected tissue is replaced (e.g., tinea capitis: 4–6 weeks; onychomycosis: 4–6 months for fingernails, 6–12 months for toenails). |
| Molecular Weight | 352.77 |
| Action Class | Antifungal Others |
| Brand Substitutes | Grisomed 250mg Tablet, Fungivin 250mg Tablet, Griseoderm 250mg Tablet, Geovin 250mg Tablet, Walavin 250mg Tablet |
500 mg orally once daily or 250 mg orally twice daily for dermatophyte infections.
| Dosage form | CAPSULE |
| Renal impairment | No dose adjustment required for renal impairment; griseofulvin is not significantly renally eliminated. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). In mild-moderate impairment, use with caution; no specific dose adjustment guidelines available. |
| Pediatric use | Children >2 years: 10-20 mg/kg/day orally in divided doses (single or twice daily). Maximum 500 mg/day. |
| Geriatric use | No specific dose adjustment; monitor for adverse effects and drug interactions due to potential polypharmacy and age-related physiological changes. |
| 1st trimester | Griseofulvin is contraindicated in the first trimester due to teratogenic effects observed in animal studies and reports of conjoined twins in humans. |
| 2nd trimester | Avoid use in the second trimester unless absolutely necessary; limited data suggest potential fetal risk. |
| 3rd trimester | Avoid use near term due to potential for fetal harm; safer alternatives should be considered. |
Clinical note
Comprehensive clinical and safety monograph for GRISACTIN (GRISACTIN).
| Placental transfer | Griseofulvin crosses the placenta; animal studies have demonstrated teratogenicity and embryotoxicity. In humans, placental transfer has been documented with detection in fetal serum. |
| Breastfeeding | Griseofulvin is excreted into breast milk in small amounts. The risk to the nursing infant is unknown, but due to potential for adverse effects on the infant's gastrointestinal tract and possible bone marrow suppression, caution is recommended. Consider alternative antifungal agents with established safety profiles. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
PorphyriaHepatocellular failureKnown hypersensitivity to griseofulvinFirst trimester pregnancy (absolute in US labeling)
| Precautions | Monitor liver function tests; hepatotoxicity possible, May exacerbate porphyria, Monitor for hypersensitivity reactions, Use cautiously in patients with penicillin allergy (potential cross-sensitivity) |
| Food/Dietary | High-fat meals significantly increase absorption of griseofulvin. Avoid alcohol during therapy due to possible disulfiram-like reaction (tachycardia, flushing). |
| Clinical Pearls |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | GRISACTIN (griseofulvin) is teratogenic in animals; in humans, first trimester exposure is associated with increased risk of conjoined twins and other malformations (limited data). Avoid use during pregnancy; particularly contraindicated in first trimester. Risk in second and third trimesters is unknown but manufacturer advises avoidance. |
| Fetal Monitoring | Monitor liver function tests (LFTs) and complete blood count (CBC) periodically in mother. For fetal assessment, if inadvertent exposure occurs, consider detailed ultrasound for structural anomalies. No specific monitoring guidelines established. |
| Fertility Effects | In animal studies, griseofulvin has caused spermatogenic arrest and decreased fertility. In humans, oligospermia and decreased sperm motility reported; may impair male fertility. Effects on female fertility unknown. |
| GRISACTIN (griseofulvin) is a fungistatic antibiotic used for dermatophyte infections. It is most effective against Trichophyton, Microsporum, and Epidermophyton species. Administer with a high-fat meal to enhance absorption. Monitor for hepatotoxicity, especially in patients with pre-existing liver disease. It induces CYP450 enzymes, potentially reducing efficacy of oral contraceptives and warfarin. Avoid use in porphyria. Duration of therapy may be several weeks to months. Interaction with alcohol may cause tachycardia and flushing. |
| Patient Advice | Take GRISACTIN with food, especially fatty foods, to improve absorption. · Complete the full course of treatment even if symptoms improve. · Avoid alcohol while taking this medication due to risk of rapid heart rate and flushing. · Use additional contraceptive measures if on oral contraceptives; GRISACTIN may reduce their effectiveness. · Report signs of liver problems: yellowing of skin/eyes, dark urine, severe nausea/vomiting. · This medication may make your skin more sensitive to sunlight; use sunscreen and protective clothing. · Do not take if you have porphyria. · Keep out of reach of children and do not share with others. |