Antitubercular agents

Question 1

What 4 medications are used in treatment of TB?

Answer 1

Isoniazid (INH)
Rifampin
Ethambutol
Pyrazinamide (PZA)

Question 2

What are the 3 subpopulations of TB?

Answer 2

Intracellular in caseating granulomas
Extracellular, rapidly dividing
Intracellular in macrophages

Question 3

Which TB drugs are working on which subpopulations of TB?

Answer 3

Intracellular in caseating granulomas- rifampin and isoniazid
Extracellular - rifampin, isoniazid, and streptomycin
Intracellular in macrophages - pyrazinamide, isoniazid, rifampin

Question 4

Which drug is dropped after susceptibility is established?

Answer 4

Drop ethambutol if there is no resistance OR drop PZA if patient has PZA intolerance but keep ethambutol

Question 5

How long does initial therapy last?

Answer 5

8 weeks

Question 6

Continuation therapy occurs after initial therapy. How long does it last and what drugs are used?

Answer 6

18 weeks of INH and rifampin

Question 7

What is the initial treatment of latent TB?

Answer 7

Isoniazid + rifapentine weekly x 12 weeks

Question 8

Alternative treatment for latent TB?

Answer 8

Rifampin daily x 4 months

Question 9

Latent TB treatment for pregnant or HIV patients?

Answer 9

INH x 6-9 months

Question 10

Treatment for multidrug resistant latent TB?

Answer 10

PZA + fluoroquinolone OR ethambutol

Question 11

Adverse reactions of isoniazid?

Answer 11

Neuritis
Hepatotoxicity
drug drug interactions vis inhibition of CYP450
allergic reactions

Question 12

What should patients take to prevent neuritis?

Answer 12

pyridoxine (vitamin B6)

Question 13

Mechanism of action of isoniazid?

Answer 13

Inhibits mycolic acid synthesis and cell wall formation

Question 14

Mechanism of action of rifampin?

Answer 14

Inhibits RNA synthesis by binding to RNA polymerase

Question 15

Rifampin works synergistically with what drug?

Answer 15

INH

Question 16

Does rifampin enhance or inhibit metabolism of drugs?

Answer 16

Enhances metabolism of drugs via P450 metabolism

Question 17

Adverse reactions to rifampin?

Answer 17

Hepatotoxicity
GI upset, rashes,
Imparts orange color to urine, sweat and tears

Question 18

What drug can HIV patients take instead of rifampin and why?

Answer 18

Rifabutin - weaker inducer of CYP450 metabolism

Question 19

What rifampin-like drug can patients take once weekly for latent TB infections?

Answer 19

Rifapentine - 5x longer half life than rifampin

Question 20

Which TB drugs are bactericidal?

Answer 20

INH, rifampin, (pyrazinamide in acidic environment of macrophages or edges of necrotic TB cavities)

Question 21

Adverse reactions to pyrazinamide?

Answer 21

hepatotoxicity
drug rash (most common of first line agents)
Hyperuricemia (gout)

Question 22

Which TB drugs are bacteriostatic?

Answer 22

Ethambutol, PZA

Question 23

Mechanism of action of ethambutol?

Answer 23

Inhibits synthesis of mycobacterial cell wall component arabinogalactan