(From Lippencott’s, by Brian Buschman)
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Isoniazid targets the development of mycolic acid which forms the wall around mycobacterium. This makes it good for M. tuberculosis and also for M. kansasii.
Resistance is due to standard lack of drug concentration intracellularly as well as target modification.
Isoniazid distributes EVERYWHERE so that it gets intracellular organisms, those in the CSF and those in caseous material.
Adverse effects of isoniazide are limited and usually only include perpheral neurotis and hepatitis. Since they target a system that does not exist in humans we don’t have many problems with them.
Rifampin blocks RNA polymerase therefore preventing transcription. It kills both M. tuberculosis and M. leprae. It is also used sometimes for various other bacteria. It is often used prophylactically for exposure (family).
It is distributed to the total body water. Adverse effects are few but it does color body fluids orange. This can stain contacts.
Pyrazinamide is used in combination with rifampin and isoniazide in TB treatment. It’s MOA is unknown but it works all over the body.
Ethambutol is another drug that can be used for TB. Like isoniazide it inhibits part of the mycobacterial cell wall.
Leprosy is usually treated with rifampin, dapsone and clofazimine.
Dapsone is a PABA antagonist used against M. leprae and PCP in HIV patients.
Clofazimine is a dye that binds DNA to block transcription. It works to help kill M. leprae and M. avium intracellulare.
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