Isoniazid dose adjustment in a pediatric population

Area of Science:

• Pharmacology
• Pediatric Medicine
• Clinical Chemistry

Background:

• Isoniazid is a cornerstone of tuberculosis treatment.
• Accurate dosing is critical for efficacy and minimizing toxicity, especially in children.
• Individual isoniazid metabolism varies significantly due to genetic factors (acetylator status).

Purpose of the Study:

• To evaluate the efficacy of the inactivation index (I3) method for adjusting isoniazid doses in pediatric patients.
• To determine if the I3 method improves plasma concentration control compared to standard dosing.
• To assess the correlation between isoniazid dose, plasma concentration, and acetylator status in children.

Main Methods:

• Retrospective analysis of 61 children receiving isoniazid therapy.
• Measurement of plasma isoniazid and acetyl isoniazid concentrations 3 hours post-dose (C3h) using high-performance liquid chromatography.
• Classification of patients into slow and fast acetylator groups based on metabolic ratio.
• Calculation of the inactivation index (I3) and recommended isoniazid dose using a validated formula.

Main Results:

• The inactivation index (I3) was significantly higher in slow acetylators compared to fast acetylators.
• Recommended isoniazid doses were significantly lower for slow acetylators (4.2 mg.kg-1) than for fast acetylators (10.3 mg.kg-1).
• Dose adjustment using the I3 method resulted in 69% of patients achieving target C3h plasma concentrations, significantly higher than the 25% in the non-adjusted group.

Conclusions:

• The inactivation index (I3) method is a reliable tool for individualizing isoniazid dosage in pediatric tuberculosis treatment.
• This method accounts for variations in isoniazid metabolism, improving therapeutic drug monitoring.
• Individualized dosing based on the I3 method enhances the likelihood of achieving optimal plasma isoniazid concentrations.