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Mechanism of Action
Isoniazid is a prodrug. This means that the drug available in the medicinal form has to be broken down into another molecule inside the body before killing the bacteria causing TB, Mycobacterium tuberculosis. The prodigy, in this case, is activated by the bacterial catalase, an enzyme secreted by the pathogen itself. The activation occurs by reducing the mycobacterial ferric KatG catalase-peroxidase enzyme by the hydrazine group in Isoniazid. Another reaction that happens simultaneously is the reaction of oxygen to create an oxy ferrous enzyme complex.
The special characteristic of Mycobacterium is the synthesis of mycolic acid in the cell wall. This is where the drug attacks specifically by inhibiting the synthesis of mycolic acid so that the bacteria does not survive and replicate further. So at the therapeutic level, the drug has a bactericidal action, i.e., it kills the tuberculosis-causing bacteria.
