Inhaled microparticles of antitubercular antibiotic for in vitro and in vivo alveolar macrophage targeting and activation of phagocytosis.

Tuberculosis (TB) is a chronic infectious disease with increasing incidence of drug resistance. Oral treatment for TB and multidrug resistance-TB can have serious side effects. The causative agent of TB, Mycobacterium tuberculosis, resides in alveolar macrophages (AMs). Pulmonary administration of antitubercular (anti-TB) antibiotic can help in delivery of high concentration to AM. The ability of AM to phagocytose can also be utilized to generate mycobactericidal nitric oxide (NO) to improve efficacy of anti-TB antibiotics. The objective in this investigation was made to prepare isoniazid microparticles (IM) and polymeric microparticles of isoniazid (INH-PM) using poly-ε-caprolactone as polymer and to evaluate in vitro through cell culture techniques and in vivo through pulmonary administration of IM and INH-PM for uptake of isoniazid by AM. The hepatotoxicity was determined through serum glutamate oxaloacetate transferase (SGOT) and serum glutamate pyruvate transferase (SGPT) levels and histological examination. The results depicted that the significantly higher (P<0.05) concentration of isoniazid was found in AM with INH-PM in vitro and in vivo. NO production was also significantly higher but less than toxic level. SGOT and SGPT levels, uptake of INH by liver and histological examination were indicative of no hepatotoxicity with INH-PM and IM. Phagocytosis of IM and INH-PM leads to significantly higher drug level in AM as well as production of significantly higher levels of NO without compromising the viability of cells. The administration of IM and INH-PM as dry powder inhalation formulation may reduce the treatment time of TB and chances of drug-resistant TB.