1. Inhibits mycolase synthetase, decreasing synthesis of mycolic acids

2. Only agent used as solo prophylaxis against TB

2. Resistance due to mutation in mycolic acid biosynthesis gene (inhA)

3. Toxicity- neurotoxicity (prevented with B6), hepatotoxicity

INH Injures Neurons and Hepatocytes

1. Inhibits DNA dependent RNAP

2. Resistance due to alteration in RNAP

3. Clinical use- TB, delays resistance to dapsone when used for leprosy, meningococcal prophylaxis and chemoprophylaxis in contacts of children with H. influenzae type B

4. Toxicity- minor hepatotoxicity, orange body fluids, drug interactions due to inc P450

5. Synergy w beta lactams for SA

Rifampin's 4 R's: RNA polymerase inhibitor, Revs up microsomal P-450, Red/orange body fluids, Rapid resistance if used alone

1. Cross-resistance with Rifampin

2. Food increases Tmax and AUC

3. Hyperuricemia

4. Inducer of CYP3A4, 2C8, 2C9

1. Large Vd and longer half life

2. Can cause Neutropenia, Leukopenia

3. Cross-resistance with rifampin

4. Induction of CYP enzymes less potent (verapamil, methadone, azoles, warfarin, OC)

5. TB in HIV infected; MAC treatment

1. Inhibits arabinogalactan

2. Optic neuritis, hyperuricemia

1. Targets fatty acid synthase I gene

2. CNS distribution, hydrolyzed then renal elim

3. Hepatotoxicity, hyperuricemia, teratogenic

1. Binds 30s ribosomal subunit

2. Given IM due to poor po absorption

3. Ototoxicity, NMB, nephrotoxicity

1. M. tuberculosis- prophylaxis is Isoniazid; treatment = Rifampin, Isoniazid, Pyrazinamide, Ethambutol, Streptomycin (RIPE for treatment); cycloserine (2nd line)

2. MAC- prophylaxis is Azithromycin; treatment = Azithromycin, rifampin, ethambutol, streptomycin

3. M leprae- No prophylaxis; treatment = Dapsone, Rifampin, Clofazimine