Posaconazole Dosing for Invasive Fungal Infections
The recommended dosage of posaconazole for invasive fungal infections depends on the formulation used, with delayed-release tablets requiring a loading dose of 300 mg twice daily on day 1, followed by 300 mg once daily maintenance dose. 1
Formulation-Specific Dosing Regimens
Delayed-Release Tablets (Preferred Formulation)
- Loading dose: 300 mg (three 100 mg tablets) twice daily on day 1
- Maintenance dose: 300 mg (three 100 mg tablets) once daily starting on day 2
- Can be administered with or without food
- Duration based on recovery from neutropenia or immunosuppression
Oral Suspension
- Initial dose: 200 mg (5 mL) four times daily for patients who are diet/nutritional supplement intolerant
- After stabilization: 400 mg (10 mL) twice daily
- Must be taken with greasy food to maximize absorption
- Failure to take with food leads to subtherapeutic levels and potential treatment failure 2
Intravenous Formulation
- Loading dose: 300 mg IV twice daily on day 1
- Maintenance dose: 300 mg IV once daily
- Appropriate for patients unable to tolerate oral therapy
Clinical Considerations
Formulation Selection
- Delayed-release tablets and IV formulations achieve higher and more reliable serum concentrations than oral suspension 3
- Oral suspension is not substitutable with delayed-release tablets due to differences in dosing and bioavailability 1
- For treatment of established invasive aspergillosis, higher doses may be needed - some data suggests 200 mg oral delayed-release tablets every 12 hours may be more effective 3
Therapeutic Drug Monitoring
- Target serum concentrations:
- ≥0.7 μg/mL for prophylaxis
- ≥1.0 μg/mL for treatment of established infection 4
- Consider monitoring in patients with poor clinical response
Special Populations
- Pediatric patients <13 years may require higher weight-based dosing:
- Delayed-release tablets: approximately 7.3 mg/kg/day
- IV formulation: approximately 9.8 mg/kg/day 4
Clinical Efficacy
- Posaconazole has demonstrated efficacy in invasive aspergillosis refractory to or intolerant of conventional therapy, with 42% success rate compared to 26% in control subjects 5
- Shows activity against CNS fungal infections with approximately 50% success rate in patients with refractory disease 6
Common Pitfalls and Caveats
- Failure to administer oral suspension with food significantly reduces absorption and effectiveness 2
- Transaminitis (mostly grade 1) occurs in approximately 67% of patients 4
- Drug interactions with triazoles may affect efficacy and safety
- Formulations are not interchangeable - prescribe the specific formulation intended
- Therapeutic drug monitoring should be considered for patients with poor clinical response or concerns about absorption
Remember that proper administration instructions and patient education are critical for successful treatment, particularly with the oral suspension formulation.