GRIS-PEG
Clinical safety rating: caution
Comprehensive clinical and safety monograph for GRIS-PEG (GRIS-PEG).
Griseofulvin binds to and disrupts microtubule function by interfering with the polymerization of tubulin, thereby inhibiting fungal cell mitosis and nucleic acid synthesis.
| Metabolism | Primarily metabolized in the liver via demethylation and glucuronidation, involving CYP450 enzymes (particularly CYP1A2). |
| Excretion | Primarily renal (as glucuronide conjugates): ~80%; fecal/biliary: ~10-15%; unchanged drug <1%. |
| Half-life | Terminal elimination half-life 14-24 hours. With continuous therapy, time to steady-state is ~3-5 days. |
| Protein binding | ~80% bound to plasma albumin (primarily) and other proteins. |
| Volume of Distribution | Vd ~1-2 L/kg, indicating extensive tissue distribution; concentrates in skin, hair, nails, and adipose tissue. |
| Bioavailability | Oral (ultramicrosize formulation): bioavailability ~75-90% (enhanced by high-fat meal). |
| Onset of Action | Oral: detectable serum levels within 2-3 hours; clinical antifungal effect begins after ~48-72 hours (requires incorporation into keratin). |
| Duration of Action | Therapeutic levels persist in keratin for weeks after discontinuation; tinea capitis treatment requires 6-8 weeks; tinea corporis 2-6 weeks. |
| Molecular Weight | 318.37 Da |
For tinea capitis and other dermatophyte infections: 500 mg oral daily as a single dose or in divided doses. For more severe infections, up to 1 g daily in divided doses.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment guidelines available. Use with caution in patients with severe renal impairment. |
| Liver impairment | Contraindicated in patients with hepatic failure. No specific Child-Pugh based modifications reported; avoid use in significant hepatic impairment. |
| Pediatric use | Children >2 years: 10-20 mg/kg/day orally in divided doses; maximum 500 mg/day for tinea capitis. For tinea pedis, 5-10 mg/kg/day. |
| Geriatric use | No specific adjustments recommended; monitor renal function and potential for adverse effects in elderly due to age-related decline in organ function. |
| 1st trimester | Avoid use; potential teratogenic effects (animal data) and risk of fetal harm. |
| 2nd trimester | Use only if clearly needed; no well-controlled human studies. |
| 3rd trimester | Avoid near term; may cause neonatal hemorrhage or kernicterus. |
Clinical note
Comprehensive clinical and safety monograph for GRIS-PEG (GRIS-PEG).
| Placental transfer | Crosses placenta; achieves fetal plasma concentrations similar to maternal. |
| Breastfeeding | Excreted into breast milk in low amounts; use caution due to potential for kernicterus in neonates, especially with G6PD deficiency. |
| Lactation Rating | L3 - Moderately Safe |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
Hypersensitivity to griseofulvin or any componentPorphyriaSevere hepatic disease
| Precautions | Hepatotoxicity: Monitor liver function tests., Photosensitivity: Avoid prolonged sun exposure., Potential for drug interactions with warfarin, oral contraceptives, and cyclosporine. |
| Food/Dietary | Take with a fatty meal (e.g., whole milk, ice cream, fried foods) to enhance absorption. Avoid alcohol during treatment due to potential disulfiram-like reaction (flushing, headache, nausea, palpitations). No other significant food interactions. |
| Clinical Pearls |
Loading safety data…
| Teratogenic Risk | First trimester: Animal studies show teratogenic effects (cleft palate, skeletal abnormalities) at high doses. Second trimester: Risk of hepatic tumors in neonates reported in some animal models. Third trimester: No specific human data; potential for hepatotoxicity. FDA Pregnancy Category C. |
| Fetal Monitoring | Monitor liver function tests (ALT, AST, ALP, bilirubin) monthly. Assess fetal growth and amniotic fluid volume via ultrasound every 4-6 weeks during pregnancy. Monitor for signs of hepatotoxicity in mother. |
| Fertility Effects | Animal studies indicate griseofulvin may impair spermatogenesis and reduce fertility in males. Effects on female fertility not well studied; potential for menstrual irregularities. |
| GRIS-PEG (griseofulvin ultramicrosize) is indicated for dermatophyte infections. Absorption is enhanced when taken with a fatty meal. Monitor for hepatotoxicity and lupus-like syndrome. Use with caution in porphyria. Avoid concurrent alcohol due to disulfiram-like reaction. |
| Patient Advice | Take with a high-fat meal to improve absorption. · Complete the full course of treatment even if symptoms improve. · Avoid alcohol during therapy and for 5 days after stopping. · Notify your doctor if you experience signs of liver problems (yellowing skin/eyes, dark urine, abdominal pain) or allergic reactions (rash, fever). · May cause photosensitivity; use sunscreen and protective clothing. · Do not take if you have porphyria or severe liver disease. · Inform your doctor if you are taking warfarin, oral contraceptives, or barbiturates. |