Abstract

^99mTc-INH of high labeling efficiency and stability has been developed using indirect method. In vitro studies and animal experiments indicated its advantages as a specific tuberculosis imaging agent. The objective of this study was to establish the efficacy of ^99mTc-INH in humans with sensitive as well as resistant tuberculosis by conducting a phase I clinical trial. The biodistribution studies were done in normal subjects and phase I clinical trial was conducted in  20 patients. Whole body scan and spots were acquired at 1 and 4 h. Angiography, blood pool and 24 h spot images of the lesion bearing areas were also acquired. The biodistribution suggested absence of in vivo breakdown of radiotracer, with main excretory pathways being hepatobiliary and renal. The biodistribution of ^99mTc-INH was similar to the unlabeled INH reported earlier. Out of 20 patients, 13 patients  with sensitive tubercular lesions in the lungs or bone and 2 patients with resistant tubercular lesion in lungs concentrated the ^99mTc-INH while in the other 5 cases with old healed lesions no concentration of ^99mTc-INH was observed in scintigraphy. An unsuspected bony lesion was discovered in a patient with known pulmonary disease. Bone lesions were visualized within 1 h while pulmonary lesions accumulated ^99mTc-INH very slowly with time and 24 h acquisition appeared essential for the diagnostic interpretation. No adverse reaction was observed in the patients post injection. ^99mTc-INH developed is safe for human use and has potential to qualify as a specific tuberculosis imaging radiopharmaceutical.

Key words: Isoniazid (INH), ^99mTc, scintigraphy, clinical trials, radiopharmaceutical.