Development and Validation of a Chromatographic Method for the Quantification of Isoniazid in Human Plasma

Objective: Isoniazid (INH) is a major antituberculosis treatment, characterized by a narrow therapeutic index and a large within and between-patient variability. Thus, Therapeutic Drug Monitoring (TDM) of this drug is mandatory in order to optimize the efficacy and minimize occurrence of toxic side effects of this drug. The aim of the present study is to develop and validate a simple chromatographic method for determination of INH in human plasma.

Methods: High performance liquid chromatography was performed using a chromatograph Ultimate 3000®. The extraction of INH from plasma was realized using trichloroacetic acid (TCA). Nicotinamide was used as an internal standard (IS). The mobile phase consisted of the buffer solution ammonium acetate (99%) 0.05 M adjusted by glacial acetic acid to pH 6 (99%), and acetonitrile (1%). The chromatographic separation was achieved on a C18 column (5 μm, 4.6 x 150 mm) at 20 °C. The signals were monitored by Diode Array Detector (DAD) at wavelength (λ) of 265 nm, at a flow rate of 1.2 ml/min.

Results: The retention times of INH and IS were 6.4 and 10.5 respectively. The limits of detection and quantification of INH were 0.09 and 0.3 μg/ml, respectively. This present method is specific and linear over the range of 0.5 to 8 μg/ml with regression coefficient of 0.998. Additionally, this method is accurate and precise, as shown by appropriate statistical tests recommended for bioanalytical methods’ validation.

Conclusion: We developed and validated a simple, rapid and convenient method for plasma INH determination in tuberculosis patients receiving this treatment.