Antimycobacterial drugs

Question 1

prophylaxis for TB

Answer 1

isoniazid.

Question 2

tx for TB

Answer 2

rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE for treatment)

Question 3

MAC prophylaxis

Answer 3

azithromycin, rifabutin.

Question 4

MAC treatment

Answer 4

more drug resistant than TB. try azithromycin or clarithromycin + ethambutol. can add rifabutin or ciprofoxacin

Question 5

M. leprae tx

Answer 5

dapsone and rifampin for tuberculoid form. add clofazimine for lepramatous.

Question 6

isoniazid MOA

Answer 6

decreases the synthesis of mycolic acids. Note that it must be metabolized to its active metabolite by bacterial catalase peroxidase

Question 7

isoniazid use and considerations

Answer 7

MTB. only agent used as solo prophylaxis against TB. different INH half-lives exist based on fast vs. slow acetylators.

Question 8

isoniazid toxicities

Answer 8

INH injures neurons and hepatocytes. see neurotoxicity and hepatotoxicity. giving pyridoxine (vit B6) can prevent neurotoxicity and lupus.

Question 9

rifamycin MOA and cosiderations

Answer 9

4 Rs of rifampin:
1. Inhibits DNA-dependent RNA polymerase
2. ramps up microsomal cytochrome P-450
3. red/orange urine and sweat
4. rapid resistance if used alone
5. rifampin ramps up the P-450 more than rifabutine, so use rifabutin in pts with HIV.
this drug is used for MTB primarily. it also delays resistance to dapsone when used for leprosy. use for prophylaxis in ppl exposed to HiB

Question 10

pyrazinamide

Answer 10

used for TB. uncertain mechanism (may acidify intracellular environment). effective in the acidic pH of phagolysosomes. toxicities include hyperuricemia and hepatotoxicity

Question 11

ethambutol: MOA, toxicity,

Answer 11

decr. carb polymerization of mycobacterium cell wall by blocking arabinosyltransferase. used against tb. causes optic neuropathy