A validated LC-MS/MS method for simultaneous quantification of antitubercular drugs in rat plasma and its application for a pharmacokinetic interaction study with Immusante^®

Tuberculosis is caused by Mycobacterium tuberculosis, and it is a contagious disease. Primary empiric treatment for tuberculosis comprises a four-drug regimen: Isoniazid, Rifampicin, Pyrazinamide, and Ethambutol. The disease and its treatment may pose undernutrition due to the increased metabolic load and decreased food intake. Immunomodulators and micronutrients are consumed by patients, worldwide, to counteract nutritional insufficiencies. Immusante^® is a polyherbal formulation recommended as an immunomodulator in various immunocompromised states, including tuberculosis. This study aims to identify the pharmacokinetic interactions between the first-line antituberculosis (anti-TB) drugs, that is, AKT-4 tablets (a combination of isoniazid, rifampicin, pyrazinamide, and ethambutol), and Immusante^®. We developed a method of sensitive liquid chromatography with tandem mass spectrometry for the simultaneous quantification of isoniazid, rifampicin, pyrazinamide, and ethambutol in rat plasma and validated it as per the European Medicines Agency guidelines. The method was used to quantify all four drugs in rat plasma treated with a combination of AKT-4 and Immusante^®. No significant alterations in the values of various pharmacokinetic parameters such as V_d, t_1/2, CL, t_max, C_max, and AUC were observed, indicating that coadministration of Immusante^® does not influence the pharmacokinetic profiles of the anti-TB drugs. Thus, Immusante^® can be recommended as an adjuvant for its immunomodulatory activity in anti-TB drug therapy.