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11 Cards in this Set
- Front
- Back
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What is the standard treatment for TB?
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0-8 weeks of 4 drugs (initial phase)
1. isoniazid 2. Rifampin 3. Ethambutol 4. Pyrazinamide 8-26 weeks (continuation phase) 1. Isoniazid 2. Rifampin |
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Why is treatment so long and with 4 drugs...
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Mycobacteria develops lesions that are hard to penetrate, simultaneous use of the drugs decreases resistance of TB
- initiation phase to counter each drug's own resistance |
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Are the 4 drugs bactericidal or bacteriostatic? When growing and when stationary/intracellular M. tuberculosis
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Growing
1. Isoniazid- cidal 2. Rifampin- cidal 3. Ethambutol- static 4. Pyrainamide- cidal Stationary/intracellular 1. Isoniazid- static 2. rifampin- cidal 3. ethambutal- static 4. pyrazinamide- cidal |
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Describe the MOA for isoniazid
Describe a mechanism of resistance? |
1. disrupts mycolic acid synthesis after M. tuberculosis activates it by katG (enzyme).
2. m tuberculosis can lose katG or overexpression of inhA or KasA from mycobacteria |
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In Isoniazid metabolism is there a pattern of certain groups of people that acetylate it fast than others?
Why is this important? What are hepatic effects? |
1. Asians are fast acetylators 90% of time
Fast metabolizes less likely to have hepatic adverse effects - related to adverse reactions- Hepatic- elevated liver enzymes, jaundice, Hepititis |
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What are Neurotoxicities of INH (Isoniazid) how are these caused?
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Neurologic-
peripheral neuritis, convulsions, neuropathy Slow pathway could cause depletion of Vitamin B6 due to Pyridoxal-phosphate depletion |
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Describe the MOA for Rifampin?
What are side/adverse effects of Rifampin? Rifampin induces CYP450... why would this be a problem? Give examples with patients taking a. oral contraceptives b. warfarin (blood thinner) c. HIV/AIDs patients |
inhibits DNA dependent- RNA polymerase (broad spectrum)
- stains things red and orange (sweat, urine, contact lenses), -CYP450 increases clearance of other drugs, a. oral contraceptives could increase chance of pregnancy b. - increasing risk for rapid coagulation in patients taking warfarin c. need to substitute Rifabutin which is weaker inducer of CYP450 |
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Describe the MOA for pyrazinamide?
What is area it is bactericidal? (nickname for drug) Adverse effects? |
uncertain- mycolic acid biosynthesis? and is bactercidal only at acidic pH "sterilizing agent"
- resistance develops if used alone - Adverse- hepatoxic (renal leads to gout) |
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Describe the MOA for ethambutol?
Adverse effects? |
inhibits arabinosyl transferases and cell wall sythesis
Adverse- optic neuritis, color disturbance, gout |
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What are general rules and examples of 2nd line TB drugs?
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never add just one drug to a failed treatment regimen, add more than one with combination of the two main primary treatments
1. fluorquinolones, ethionamide, PAS (para-aminosalicyclic acid), cycloserine, aminoglycosides, capreomycin |
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a. How do you treat pregnant women with TB?
b. HIV + TB |
a. 3 drugs - isoniazid, rifampim, ethambutol
b. first TB treatment, then HIV, avoid INH-rifapentine and INH-rifampin if CD4 count is low |
