GRISACTIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for GRISACTIN (GRISACTIN).

How it works

Binds to microtubules and disrupts mitotic spindle formation, inhibiting fungal cell division.

What the body does with it

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).

Classification & Brands

Action Class	Antifungal Others
Brand Substitutes	Grisomed 250mg Tablet, Fungivin 250mg Tablet, Griseoderm 250mg Tablet, Geovin 250mg Tablet, Walavin 250mg Tablet

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for GRISACTIN (GRISACTIN).

Breastfeeding	Griseofulvin is excreted into breast milk; milk-to-plasma ratio approximately 0.5. Potential for adverse effects in nursing infant (e.g., hepatotoxicity, carcinogenicity). Contraindicated during breastfeeding; alternative antifungal therapy recommended.
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.

Warnings & precautions

■ FDA Black Box Warning

No FDA black box warning.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to griseofulvin","Porphyria","Hepatic failure","Pregnancy (teratogenic)"]

Clinical Precautions

Precautions

["Monitor liver function tests; hepatotoxicity possible","May exacerbate porphyria","Monitor for hypersensitivity reactions","Use cautiously in patients with penicillin allergy (potential cross-sensitivity)"]

Clinical Tips & Counseling

Drug interactions

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GRISACTIN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for GRISACTIN (GRISACTIN).

How it works

Binds to microtubules and disrupts mitotic spindle formation, inhibiting fungal cell division.

What the body does with it

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).

Classification & Brands

Action Class	Antifungal Others
Brand Substitutes	Grisomed 250mg Tablet, Fungivin 250mg Tablet, Griseoderm 250mg Tablet, Geovin 250mg Tablet, Walavin 250mg Tablet

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for GRISACTIN (GRISACTIN).

Breastfeeding	Griseofulvin is excreted into breast milk; milk-to-plasma ratio approximately 0.5. Potential for adverse effects in nursing infant (e.g., hepatotoxicity, carcinogenicity). Contraindicated during breastfeeding; alternative antifungal therapy recommended.
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.

Warnings & precautions

■ FDA Black Box Warning

No FDA black box warning.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to griseofulvin","Porphyria","Hepatic failure","Pregnancy (teratogenic)"]