Anti-TB drugs

Question 1

What is the primary mode of resistance of M. TB to INH?

Answer 1

deletion in katG gene → no catalase → isoniazid can’t be activated

Question 2

What is the most common prescribed drug to cause B6 deficiency? What drug of abuse does this?

Answer 2

Isoniazid because it ↑ liver transaminase activity for the 6-12 mo. it is taken for TB, depleting B6 as a required cofactor; EtOH is the most common cause of B6 deficiency overall

Question 3

What happens when you run out of vitamin B6?

Answer 3

1. ammonia can’t be detoxified → peripheral neuritis
2. can’t build heme → sideroblastic anemia (b/c iron not used → iron-laden erythroblasts in bone marrow; labs ↑ serum iron, % sat, ferritin; ↓ TIBC)

Question 4

What is a rare side effect that might occur with isoniazid use in slow acetylators?

Answer 4

SLE

Question 5

Patients with what genetic condition should be careful when taking isoniazid?

Answer 5

G6PD deficiency → can cause acute hemolysis

Question 6

What three TB drugs cause hepatotoxicity?

Answer 6

INH, rifampin, and pyrazinamide

Question 7

Which TB drug is a weak acid that causes hyperuricemia?

Answer 7

pyrazinamide

Question 8

What drug is used as an IV infusion for TB in the hospital (not for the long course combo tx)?

Answer 8

Streptomycin

Question 9

What are the main side effects of streptomycin?

Answer 9

neuromuscular blockade by ↓ ACh release: deafness, vestibular dysfunction
nephrotoxicity