What is the suitable liquid itraconazole (antifungal medication) dose for a 9-year-old male weighing 74.6 pounds, originally prescribed 100 MG itraconazole capsules once daily?

Liquid Itraconazole Dosing for 9-Year-Old Child

For this 9-year-old weighing 74.6 lbs (33.8 kg), convert to itraconazole oral solution at 5 mg/kg/day divided into two doses (approximately 85 mg twice daily, rounded to practical volume of 8.5 mL twice daily of the 10 mg/mL solution) for the same 14-day duration. 1

Weight-Based Dosing Calculation

• Patient weight: 74.6 lbs = 33.8 kg
• Recommended pediatric dose: 5 mg/kg/day in two divided doses for children ≥2 years 1
• Total daily dose: 33.8 kg × 5 mg/kg = 169 mg/day
• Divided dose: 84.5 mg (approximately 85 mg) twice daily 1

Practical Liquid Formulation Dosing

• Itraconazole oral solution concentration: 10 mg/mL 2
• Volume per dose: 8.5 mL twice daily (85 mg per dose)
• Administration: Take on an empty stomach (without food if possible) for optimal absorption 2
• Duration: Continue for 14 days as originally prescribed 2

Critical Differences Between Capsules and Solution

The oral solution and capsules are NOT interchangeable. 2 The solution has superior bioavailability compared to capsules, particularly in children, and should be dosed differently 1, 3. The original 100 mg capsule once daily is underdosing for a child of this weight when using the solution formulation.

Therapeutic Drug Monitoring Recommendation

Therapeutic drug monitoring (TDM) is strongly suggested for pediatric patients receiving itraconazole. 1 Target trough concentration should be ≥0.5 mg/L 1. This is particularly important because:

• Children have different pharmacokinetics than adults, with faster clearance 1
• Absorption can be variable even with the solution formulation 3
• The indication for treatment is not specified, and adequate drug levels ensure therapeutic efficacy 1

Administration Instructions

• Swish vigorously in mouth (if treating oropharyngeal candidiasis) before swallowing 2
• Take without food when possible for maximum absorption 2
• Do not substitute with capsule formulation at equivalent doses 2
• Administer doses approximately 12 hours apart 1

Important Caveats

Itraconazole is not FDA-approved for patients <18 years in the United States, though it is widely used off-label in pediatric populations with extensive safety data. 1 The European guidelines specifically address pediatric dosing for children ≥2 years of age. 1

Monitor for drug interactions if the child is taking other medications, particularly those metabolized by CYP3A4 (including certain antihistamines, immunosuppressants, or other azoles). 1

Assess hepatic and renal function before initiating therapy, as limited data exist for itraconazole use in patients with impairment. 2