GRISACTIN ULTRA

Clinical safety rating: caution

Comprehensive clinical and safety monograph for GRISACTIN ULTRA (GRISACTIN ULTRA).

How it works

Griseofulvin binds to tubulin and disrupts microtubule function, inhibiting fungal cell division and nucleic acid synthesis.

What the body does with it

Metabolism	Metabolized in the liver via glucuronidation; induces cytochrome P450 enzymes (CYP3A4, CYP1A2, CYP2C9, CYP2C19).
Excretion	Primarily hepatic metabolism; less than 1% excreted unchanged in urine; approximately 30-50% of a dose is eliminated in feces as metabolites, with minor biliary excretion.
Half-life	Terminal elimination half-life ranges from 6.5 to 9 hours (mean ~7.5 hours) in patients with normal hepatic function; prolonged in hepatic impairment.
Protein binding	Extensively bound (>99%) mainly to serum albumin; also binds to corticosteroid-binding globulin.
Volume of Distribution	Apparent volume of distribution (Vd) is approximately 1.5 to 2 L/kg, indicating extensive tissue distribution and lipid solubility.
Bioavailability	Oral bioavailability is variable due to poor aqueous solubility; micronized formulation (GRISACTIN ULTRA) yields improved absorption, with estimates of 25-70% (mean ~50%); absorption enhanced by fatty meal.
Onset of Action	Clinical effect (decrease in pruritus) typically seen within 24 hours after oral administration; measurable griseofulvin in plasma within 30 minutes, peak at 4 hours.
Duration of Action	Duration of therapeutic effect: approximately 12 to 24 hours after a single oral dose; requires continuous daily dosing for fungistatic effect; treatment duration for tinea infections is 4-6 weeks for skin, up to 12 months for nails.

Classification & Brands

Dosing & administration

500 mg orally once daily or 250 mg orally twice daily; for severe infections, 500 mg twice daily or 250 mg three times daily. Maximum daily dose: 1 g. Administer with or after meals.

Dosage form	TABLET
Renal impairment	No dose adjustment for GFR ≥50 mL/min. For GFR 10-49 mL/min: decrease dose by 50% (e.g., 250 mg daily). For GFR <10 mL/min: administer 125 mg daily. Hemodialysis: no supplemental dose needed.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% (e.g., 250 mg daily). Child-Pugh C: contraindicated or avoid use.
Pediatric use	Children >2 years: 10-15 mg/kg orally once daily or divided twice daily (maximum 750 mg/day). Weight-based: 5-7.5 mg/kg every 12 hours. Administer with meals.
Geriatric use	Start at lower end of dosing range (250 mg daily) due to age-related renal decline; monitor renal function and adjust per creatinine clearance.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for GRISACTIN ULTRA (GRISACTIN ULTRA).

Breastfeeding	Excreted in breast milk; M/P ratio approximately 0.3-0.5. Potential for adverse effects in nursing infants (hepatic, hematologic). Contraindicated during breastfeeding unless benefit outweighs risk.
Teratogenic Risk	Category X. Contraindicated in pregnancy. Associated with fetal abnormalities including conjoined twins, CNS defects, and spontaneous abortion. Risk is highest during first trimester; use during second and third trimesters may cause fetal hepatotoxicity and growth restriction.

Warnings & precautions

■ FDA Black Box Warning

None.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to griseofulvin or any component.","Severe liver disease.","Porphyria.","Pregnancy (risk of fetal harm; advise effective contraception)."]

Clinical Precautions

Precautions

["Hepatotoxicity risk; monitor liver function.","May exacerbate systemic lupus erythematosus.","Can cause photosensitivity reactions.","Potential for cross-sensitivity with penicillins; use with caution in penicillin-allergic patients.","May interact with warfarin, oral contraceptives, and alcohol."]

Clinical Tips & Counseling

Drug interactions

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GRISACTIN ULTRA

Clinical safety rating: caution

Comprehensive clinical and safety monograph for GRISACTIN ULTRA (GRISACTIN ULTRA).

How it works

Griseofulvin binds to tubulin and disrupts microtubule function, inhibiting fungal cell division and nucleic acid synthesis.

What the body does with it

Metabolism	Metabolized in the liver via glucuronidation; induces cytochrome P450 enzymes (CYP3A4, CYP1A2, CYP2C9, CYP2C19).
Excretion	Primarily hepatic metabolism; less than 1% excreted unchanged in urine; approximately 30-50% of a dose is eliminated in feces as metabolites, with minor biliary excretion.
Half-life	Terminal elimination half-life ranges from 6.5 to 9 hours (mean ~7.5 hours) in patients with normal hepatic function; prolonged in hepatic impairment.
Protein binding	Extensively bound (>99%) mainly to serum albumin; also binds to corticosteroid-binding globulin.
Volume of Distribution	Apparent volume of distribution (Vd) is approximately 1.5 to 2 L/kg, indicating extensive tissue distribution and lipid solubility.
Bioavailability	Oral bioavailability is variable due to poor aqueous solubility; micronized formulation (GRISACTIN ULTRA) yields improved absorption, with estimates of 25-70% (mean ~50%); absorption enhanced by fatty meal.
Onset of Action	Clinical effect (decrease in pruritus) typically seen within 24 hours after oral administration; measurable griseofulvin in plasma within 30 minutes, peak at 4 hours.
Duration of Action	Duration of therapeutic effect: approximately 12 to 24 hours after a single oral dose; requires continuous daily dosing for fungistatic effect; treatment duration for tinea infections is 4-6 weeks for skin, up to 12 months for nails.

Classification & Brands

Dosing & administration

500 mg orally once daily or 250 mg orally twice daily; for severe infections, 500 mg twice daily or 250 mg three times daily. Maximum daily dose: 1 g. Administer with or after meals.

Dosage form	TABLET
Renal impairment	No dose adjustment for GFR ≥50 mL/min. For GFR 10-49 mL/min: decrease dose by 50% (e.g., 250 mg daily). For GFR <10 mL/min: administer 125 mg daily. Hemodialysis: no supplemental dose needed.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% (e.g., 250 mg daily). Child-Pugh C: contraindicated or avoid use.
Pediatric use	Children >2 years: 10-15 mg/kg orally once daily or divided twice daily (maximum 750 mg/day). Weight-based: 5-7.5 mg/kg every 12 hours. Administer with meals.
Geriatric use	Start at lower end of dosing range (250 mg daily) due to age-related renal decline; monitor renal function and adjust per creatinine clearance.

Use during pregnancy

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

Clinical note

Comprehensive clinical and safety monograph for GRISACTIN ULTRA (GRISACTIN ULTRA).

Breastfeeding	Excreted in breast milk; M/P ratio approximately 0.3-0.5. Potential for adverse effects in nursing infants (hepatic, hematologic). Contraindicated during breastfeeding unless benefit outweighs risk.
Teratogenic Risk	Category X. Contraindicated in pregnancy. Associated with fetal abnormalities including conjoined twins, CNS defects, and spontaneous abortion. Risk is highest during first trimester; use during second and third trimesters may cause fetal hepatotoxicity and growth restriction.

Warnings & precautions

■ FDA Black Box Warning

None.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to griseofulvin or any component.","Severe liver disease.","Porphyria.","Pregnancy (risk of fetal harm; advise effective contraception)."]