Pharmacokinetic study of isoniazid and pyrazinamide in children: impact of age and nutritional status.

OBJECTIVES: To evaluate pharmacokinetics of first-line antitubercular drugs, isoniazid (INH) and pyrazinamide (PZA), with revised WHO dosages and to assess its adequacy in relation to age and nutritional status.
DESIGN: Observational study.
SETTING: This study was conducted at Sarojini Naidu Medical College, Agra, and National Institute for Research in Tuberculosis, Chennai. PATIENTS: 40 subjects diagnosed with tuberculosis were registered in the study and started on daily first-line antitubercular regimen based on the revised WHO guidelines.
INTERVENTIONS: Blood samples were collected at 0, 2, 4, 6 and 8 hours from these subjects after 15 days of treatment for drug estimations. MAIN OUTCOME MEASURE: The measurement of drug concentrations (maximum peak concentration (Cmax) and area under the time -concentration curve (AUC0-8 hours)) for INH and PZA. Appropriate statistical methods were used to evaluate the impact of age and nutritional status on pharmacokinetic variables.
RESULTS: For INH, the difference in drug exposures in children <3 years (Cmax 3.18 µg/mL and AUC0-8 hours15.76 µg/mL hour) and children >3 years (Cmax3.05 µg/mL and AUC0-8 hours 14.37 µg/mL hour) was not significant (P=0.94, P=0.81, respectively). The drug levels in children with low body mass index (BMI) (Cmax3.08 µg/mL; AUC0-8 hours14.81 µg/mL hour) were also comparable with their normal counterparts (Cmax3.09 µg/mL, P=0.99; AUC0-8 hours 14.69 µg/mL hour, P=0.82). PZA drug exposures obtained in children less than 3 years (Cmax29.22 µg/mL, AUC0-8 hours 155.45 µg/mL hour) were significantly lower compared with drug levels in children above 3 years (Cmax 37.12 µg/mL, P=0.03; AUC 202.63 µg/mL hour, P value=0.01). Children with low BMI had significantly lower drug concentrations (Cmax 31.90 µg/mL, AUC0-8 hours167.64 µg/mL hour) when compared with normal counterparts (Cmax 37.60 µg/mL, P=0.02; AUC0-8 hours 208.77 µg/mL hour, P=0.01).
CONCLUSIONS: The revised WHO drug dosages were found to be adequate for INH with respect to age and nutritional status, whereas PZA showed significantly lower drug levels in children <3 years and in malnourished children. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.