FULVICIN P/G
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FULVICIN P/G (FULVICIN P/G).
Binds to microtubule-associated proteins, disrupting mitotic spindle formation and inhibiting fungal cell division.
| Metabolism | Hepatic metabolism primarily via CYP enzymes, including CYP1A2 and CYP3A4 |
| Excretion | Renal (largely unchanged, <1% as metabolites); biliary/fecal (minor). Approximately 36% of a dose is excreted in urine within 6 hours, and up to 50% within 72 hours. |
| Half-life | Terminal elimination half-life: 9–24 hours (mean ~16 hours). Clinical context: prolonged half-life allows once-daily dosing; steady-state achieved within 2–3 days. |
| Protein binding | Highly protein-bound: approximately 97–99%, primarily to albumin. |
| Volume of Distribution | Vd: approximately 1.0 L/kg, indicating extensive tissue distribution, particularly to skin, hair, and nails. |
| Bioavailability | Oral: bioavailable fraction highly variable (20–80%) due to poor aqueous solubility and first-pass metabolism; absorption enhanced with fatty meals. |
| Onset of Action | Oral: detectable epidermal levels in 4–8 hours; clinical improvement of tinea infections usually within 2–4 weeks. |
| Duration of Action | Duration: up to 7 days after last dose due to accumulation in keratin; continued treatment required for 4–8 weeks for most dermatophyte infections. |
250 mg orally twice daily for tinea infections; 500 mg orally twice daily for onychomycosis. Administer with a fatty meal to enhance absorption.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. For severe impairment (GFR <30 mL/min), consider alternative therapy due to limited data; use with caution. |
| Liver impairment | Contraindicated in patients with Child-Pugh class B or C cirrhosis. For Child-Pugh class A, reduce dose by 50% and monitor liver function. |
| Pediatric use | For children ≥2 years: 10 mg/kg/day orally in divided doses (twice daily) for tinea infections; up to 20 mg/kg/day for severe infections. Maximum 1 g/day. |
| Geriatric use | No specific dose adjustment. Monitor renal and hepatic function due to age-related decline; consider lower end of dosing range to avoid accumulation. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for FULVICIN P/G (FULVICIN P/G).
| Breastfeeding | Griseofulvin is excreted in breast milk; M/P ratio unknown. Potential for adverse effects in nursing infant (e.g., hepatotoxicity, bone marrow suppression). Discontinue breastfeeding or avoid use. Use only if clearly needed with monitoring of infant. |
| Teratogenic Risk | FULVICIN P/G (griseofulvin) is contraindicated in pregnancy. First trimester: High risk of teratogenicity based on animal studies (multiple congenital anomalies, including conjoined twins in dogs). Second and third trimesters: Avoid due to potential fetal harm; no well-controlled human studies. Consider alternative therapy. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to griseofulvin or any component","Porphyria","Hepatic failure","Pregnancy (category C; avoid in pregnancy due to teratogenicity risk)"]
| Precautions | ["Hepatotoxicity","Photosensitivity reactions","Lupus erythematosus exacerbation","Hematologic effects (leukopenia, neutropenia)","Monitoring hepatic function recommended"] |
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| Fetal Monitoring | Monitor maternal liver function tests (LFTs), complete blood count (CBC) with differential, and renal function periodically. Assess for signs of hepatotoxicity or blood dyscrasias. Fetal monitoring with ultrasound if inadvertent exposure during pregnancy. |
| Fertility Effects | Animal studies show reduced spermatogenesis and testicular changes at high doses; human data limited. May impair fertility in males. Effects on female fertility not well characterized. |