Griseofulvin Dosing for Pediatric Ringworm
For your 35 kg, 8-year-old patient with ringworm, give griseofulvin 700 mg daily (20 mg/kg/day) with a fatty meal for 6-8 weeks. 1
Specific Dosing Calculation
- Standard dose: 20 mg/kg/day in single or divided doses for patients under 50 kg 1, 2
- For this 35 kg patient: 700 mg daily (35 kg × 20 mg/kg = 700 mg)
- Duration: 6-8 weeks for tinea capitis (scalp ringworm) 1
- Administration: Give with fatty food to enhance absorption and bioavailability 1, 2, 3
Dosing Range and Adjustments
- The British Association of Dermatologists guidelines specify 15-20 mg/kg/day as the standard range 2, 4
- May increase up to 25 mg/kg/day (875 mg for this patient) for resistant cases or prolonged treatment 1, 2
- Can be given as single daily dose or divided doses 1
Critical Treatment Considerations
Species-Specific Efficacy
- Microsporum species: 88.5% response rate with griseofulvin 1
- Trichophyton species: 67.9% response rate - may require higher doses (up to 25 mg/kg/day) and longer duration (12-18 weeks) 1, 2
- Treatment should ideally be guided by culture results, though empiric therapy is reasonable with typical clinical features 1
Administration Pearls
- Fatty meal significantly increases absorption: In pediatric studies, giving griseofulvin with milk resulted in 4-fold higher peak serum concentrations and 10-fold larger area under the curve compared to fasting administration 3
- Peak serum levels occur approximately 4 hours after oral administration 3, 4
Safety Profile
Common Side Effects
- Gastrointestinal disturbances and rashes in <8% of patients 1
- Headaches may occur 2, 4
- Very few patients (0.8%) require discontinuation 1
- Well-tolerated in children 4
Contraindications
Drug Interactions
- Rifampicin decreases plasma concentration 1, 2
- Cimetidine increases plasma concentration 1, 2
- Barbiturates decrease griseofulvin activity 3
Treatment Monitoring
- Endpoint should be mycological cure, not just clinical improvement 1, 2
- Repeat mycology sampling recommended until clearance is achieved 1, 2
- Consider treatment failure causes: non-compliance, suboptimal absorption, organism resistance, or reinfection 2
Adjunctive Measures
- Add topical antifungal shampoo (ketoconazole 2%, selenium sulfide 1%, or povidone-iodine) to reduce spore transmission 1
- Screen and treat family members - over 50% may be affected with anthropophilic species like T. tonsurans 1
- Disinfect hairbrushes and combs with bleach or 2% sodium hypochlorite solution 1
- Child can attend school while on appropriate systemic and topical therapy 1
Formulation Notes
- Griseofulvin is available as micronized, ultramicronized, and suspension forms 1
- The suspension allows more accurate dosage adjustments in children but has become increasingly expensive and less available 1
- Griseofulvin remains the only licensed product for tinea capitis in children in many countries 1, 2