What is the recommended dosage and treatment duration of griseofulvin for a 14-year-old patient with fungal infections of the skin, hair, and nails?

Griseofulvin Prescribing Information for a 14-Year-Old with Fungal Infections

For a 14-year-old with fungal infections of the skin, hair, and nails, griseofulvin should be prescribed at a dose of 15-20 mg/kg/day for 6-8 weeks for tinea capitis, and 10 mg/kg/day for 6-9 months for fingernail infections or 12-18 months for toenail infections. 1

Dosing Guidelines by Infection Type

Tinea Capitis (Scalp Fungal Infection)

• For patients <50 kg: 15-20 mg/kg/day in single or divided doses for 6-8 weeks 1
• For patients >50 kg: 1 g/day in single or divided doses for 6-8 weeks 1
• Higher doses up to 25 mg/kg/day may be required for resistant cases or prolonged treatment periods 1
• Griseofulvin is particularly effective against Microsporum species (88.5% response rate) compared to Trichophyton species (67.9%) 1

Onychomycosis (Nail Fungal Infection)

• For children aged 1 month and above: 10 mg/kg/day (maximum 500 mg) 1
• Treatment duration: 6-9 months for fingernail infections and 12-18 months for toenail infections 1
• Note: While griseofulvin is licensed for children with onychomycosis, newer antifungals may be more effective for nail infections 1

Administration Guidelines

• Take with fatty food to increase absorption and improve bioavailability 1, 2
• Available in several forms (micronized, ultramicronized and suspension) 1
• Absorption is enhanced when administered with a fatty meal 2

Efficacy Considerations

• Griseofulvin remains the only licensed product for treating tinea capitis in children in many countries 1
• For tinea capitis caused by Trichophyton species, higher doses for longer periods (12-18 weeks) may be required 1
• For onychomycosis, mycological cure rates are only 30-40% for toenail infections 1
• Studies comparing griseofulvin with newer antifungals have demonstrated lower cure rates for griseofulvin in nail infections 1

Safety Profile

• Generally well-tolerated, particularly in children 2
• Common side effects (mild to moderate):
  • Gastrointestinal disturbances 1, 3
  • Headaches 1, 2
  • Skin rashes in <8% of patients 1, 2
• Discontinuation due to adverse effects is rare 3

Contraindications

• Lupus erythematosus 1
• Porphyria 1
• Severe liver disease 1

Drug Interactions

• Plasma concentration decreased by rifampicin 1
• Plasma concentration increased by cimetidine 1
• Interactions with phenobarbital, anticoagulants, and oral contraceptives 2

Treatment Monitoring

• The endpoint of treatment should be mycological rather than clinical cure 1
• Repeat mycology sampling is recommended until mycological clearance is achieved 1
• For resistant cases, consider:
  • Lack of compliance
  • Suboptimal absorption
  • Relative insensitivity of the organism
  • Reinfection 1

Important Considerations

• For tinea capitis, topical therapy alone is not recommended; oral therapy is generally indicated 1
• Choice of systemic therapy should be directed by the causative dermatophyte species 1
• For nail infections in children, griseofulvin is considered as second-line if itraconazole and terbinafine are contraindicated or not tolerated 1