Griseofulvin

# Griseofulvin ## Overview - **Classification**: Antifungal, fungistatic agent. - **Mechanism**: Inhibits fungal cell mitosis by disrupting microtubule assembly. Accumulates in keratin precursor cells, making new keratin resistant to fungal infection. ## Primary Indications 1. **Dermatophytosis**: Tinea infections of skin, hair (tinea capitis), and nails (onychomycosis). 2. **Refractory Superficial Fungal Infections**: When topical agents are ineffective or infection is widespread. ## Adult Dosing ### Standard Dosing **Tinea Corporis, Tinea Cruris, Tinea Pedis (Microsize)** - **Dose**: **500 mg/day** - **Frequency**: Once daily or divided BID - **Route**: Oral - **Duration**: 2-4 weeks, or until clinical and mycological cure. **Tinea Corporis, Tinea Cruris, Tinea Pedis (Ultramicrosize)** - **Dose**: **330-375 mg/day** - **Frequency**: Once daily or divided BID - **Route**: Oral - **Duration**: 2-4 weeks, or until clinical and mycological cure. **Tinea Capitis, Onychomycosis, Severe Tinea Pedis (Microsize)** - **Dose**: **750-1000 mg/day** - **Frequency**: Divided BID - **Route**: Oral - **Duration**: Tinea Capitis: 4-8 weeks; Onychomycosis: 4-6 months (fingernails), 6-12 months (toenails). **Tinea Capitis, Onychomycosis, Severe Tinea Pedis (Ultramicrosize)** - **Dose**: **660-750 mg/day** - **Frequency**: Divided BID - **Route**: Oral - **Duration**: Tinea Capitis: 4-8 weeks; Onychomycosis: 4-6 months (fingernails), 6-12 months (toenails). ### Dose Adjustments - **Renal Impairment**: No specific dose adjustment required. Use with caution. - **Hepatic Impairment**: **Contraindicated** in severe liver disease. Use with caution in mild-moderate impairment. - **Elderly Patients**: No specific dose adjustment, but monitor for liver function and drug interactions. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: Not recommended. - **Special Notes**: Safety and efficacy not established in this age group. ### Infants (1-12 months) - **Dose**: **10-15 mg/kg/day** (microsize) or **5-10 mg/kg/day** (ultramicrosize) - **Frequency**: Once daily or divided BID - **Maximum**: **750 mg/day** (both microsize and ultramicrosize) - **Special Notes**: Often used for tinea capitis. Oral suspension available. ### Children (1-12 years) - **Dose**: **10-20 mg/kg/day** (microsize) or **5-15 mg/kg/day** (ultramicrosize) - **Frequency**: Once daily or divided BID - **Maximum**: **1000 mg/day** (microsize); **750 mg/day** (ultramicrosize) - **Special Notes**: Dose based on severity and site. Oral suspension preferred for younger children. ### Adolescents (13-18 years) - **Dose**: Follow **adult dosing recommendations**. - **Maximum**: **1000 mg/day** (microsize); **750 mg/day** (ultramicrosize) ## Safety Information ### Contraindications - **Absolute**: **Porphyria**. - **Absolute**: **Severe hepatocellular disease** or liver failure. - **Absolute**: **Pregnancy** (Category X) due to teratogenicity. - **Absolute**: Hypersensitivity to griseofulvin. ### Common Adverse Effects - **Very Common (>10%)**: Headache, nausea, vomiting, diarrhea. - **Common (1-10%)**: Photosensitivity, skin rash, urticaria, dizziness, fatigue, heartburn. - **Serious but Rare**: Hepatotoxicity (elevated LFTs, jaundice), leukopenia, neutropenia, proteinuria, angioedema. ### Key Drug Interactions - **Warfarin**: **Decreases anticoagulant effect** of warfarin. Monitor INR closely; may require warfarin dose increase. - **Oral Contraceptives**: **Decreases efficacy** of oral contraceptives. Advise alternative birth control during and for 1 month post-therapy. - **Barbiturates (e.g., Phenobarbital)**: **Decreases griseofulvin absorption**. May require higher griseofulvin dose. - **Alcohol**: May cause **disulfiram-like reaction** (flushing, tachycardia). Avoid alcohol during therapy. ## Monitoring & Follow-up - **Before Treatment**: Baseline **Liver Function Tests (LFTs)**, **CBC with differential**. - **During Treatment**: Periodically monitor **LFTs** (e.g., every 4-8 weeks for prolonged therapy) and **CBC** (e.g., every 4 weeks). - **Clinical Signs**: Monitor for signs of liver injury (e.g., jaundice, dark urine, severe fatigue), severe rash, or other adverse effects. ## Clinical Pearls - 💡 **Tip 1**: Administer **with a fatty meal** (e.g., milk, butter, peanut butter) to significantly enhance absorption. - 💡 **Tip 2**: Advise patients on **photosensitivity**; recommend sunscreen and protective clothing when outdoors. - 💡 **Tip 3**: For tinea capitis, treatment is prolonged; consider adjunct use of medicated shampoos (e.g., selenium sulfide). - 💡 **Tip 4**: Emphasize **adherence** for the full duration, especially for nail infections, to prevent recurrence. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.