FULVICIN P/G 165
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FULVICIN P/G 165 (FULVICIN P/G 165).
Griseofulvin binds to and disrupts microtubule function by inhibiting spindle formation and mitosis in dermatophytes, leading to inhibition of fungal cell division.
| Metabolism | Primarily hepatic, via demethylation and glucuronidation; multiple metabolites; CYP450 involvement not fully characterized. |
| Excretion | Primarily renal excretion of metabolites; <1% excreted unchanged. Biliary/fecal elimination accounts for ~30% of metabolites. |
| Half-life | Terminal elimination half-life is approximately 9-24 hours; dependent on formulation and absorption rate. Steady-state achieved within 4-5 days. |
| Protein binding | 90-95% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Apparent Vd is 0.5-1.5 L/kg; indicates extensive tissue distribution (skin, hair, nails). |
| Bioavailability | Oral bioavailability of ultramicrosized formulation (P/G 165) is approximately 80-90%; absorption enhanced by fatty meal. |
| Onset of Action | Oral: detectable serum levels within 4 hours; clinical improvement in tinea infections may take 1-2 weeks. |
| Duration of Action | Duration of therapeutic effect post last dose is approximately 2-4 days; entire treatment course typically 4-8 weeks depending on infection site. |
| Molecular Weight | 352.77 |
165 mg orally once daily.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for renal impairment. |
| Liver impairment | Contraindicated in patients with severe liver disease; use with caution in mild to moderate hepatic impairment with dose reduction as clinically indicated. |
| Pediatric use | Not recommended for children under 2 years. For children 2 years and older: 10-20 mg/kg/day in divided doses. |
| Geriatric use | Use with caution due to increased risk of adverse effects; consider lower starting doses and monitor renal function. |
| 1st trimester | Contraindicated: griseofulvin is teratogenic in animal studies; avoid use. |
| 2nd trimester | Contraindicated: potential fetal harm; avoid use. |
| 3rd trimester | Contraindicated: avoid use near term due to risk of fetal harm. |
Clinical note
Comprehensive clinical and safety monograph for FULVICIN P/G 165 (FULVICIN P/G 165).
| Placental transfer | Griseofulvin crosses the placenta; teratogenic in animal models. |
| Breastfeeding | Griseofulvin is excreted in breast milk; avoid breastfeeding during treatment due to potential adverse effects in the infant. |
| Lactation Rating | L5 (Contraindicated) |
■ FDA Black Box Warning
No FDA black box warning exists for griseofulvin.
| Serious Effects |
Pregnancy or possibility thereofPorphyriaHepatocellular failureHistory of hypersensitivity to griseofulvin
| Precautions | Hepatotoxicity: monitor liver function tests, Photosensitivity: avoid prolonged sun exposure, Lupus-like syndrome exacerbation, Blood dyscrasias: monitor CBC with long-term therapy, Potential for teratogenicity; avoid use in pregnancy |
| Food/Dietary | Griseofulvin absorption is significantly increased by high-fat meals. Take with whole milk, ice cream, or fatty foods. Do not take with low-fat meals. Avoid alcohol due to risk of disulfiram-like reaction and hepatotoxicity. |
Loading safety data…
| Teratogenic Risk | First trimester: Known teratogen in animals; human data limited but suggests increased risk of conjoined twins and other malformations. Second and third trimesters: Potential fetal hepatotoxicity; avoid use. |
| Fetal Monitoring | Monitor liver function tests (LFTs) monthly; fetal ultrasound for anomalies if exposed in first trimester; monitor for signs of maternal hepatotoxicity. |
| Fertility Effects | May cause reversible sperm abnormalities and reduce fertility in males; no data in females. |
| Clinical Pearls |
| Fulvicin P/G 165 (griseofulvin ultramicrosize) is indicated for dermatophyte infections unresponsive to topical therapy. Administer with a high-fat meal to enhance absorption. Monitor for lupus-like syndrome, photosensitivity, and hepatic toxicity. Avoid concurrent use with warfarin, oral contraceptives, and alcohol. Ultramicrosize formulation allows lower dosing compared to microsize. |
| Patient Advice | Take with fatty foods like milk or peanut butter to improve absorption. · Complete the full course even if symptoms improve. · Avoid prolonged sun exposure and use sunscreen; may cause photosensitivity. · Report signs of lupus-like reaction (joint pain, rash, fever) or liver issues (dark urine, jaundice). · May reduce effectiveness of oral contraceptives; use additional non-hormonal birth control. · Avoid alcohol during treatment. |