(7) Antimicrobials: Antimicrobacterials (3.1-3.2)

Question 1

What drug regimen is most commonly used to treat active tuberculosis?

Answer 1

(1) Rifampin
(2) Isoniazid
(3) Pyrazinamide
(4) Ethambutol
* (And Vitamin B6)*

Question 2

What are the two phases of treatment for tuberculosis?

Answer 2

(1) 4 drugs for 2 months
(2) 2 drugs for 4 months

Question 3

What antibiotic can be used alone to treat latent tuberculosis infections?

Answer 3

Isoniazid

(“Remember, Isoniazid can be used isolated”)

Question 4

MOA: Isoniazid

Answer 4

Inhibits the synthesis of mycolic acid

(Note: Pyrazinamide has the same MOA, but acts immediately upstream of INH)

Question 5

What antibiotic is activated by catalase-peroxidase?

Answer 5

Isoniazid

Question 6

Resistance: Isoniazid

Answer 6

Downregulation of Kat G

(Kat G ≡ catalase-peroxidase)

Question 7

Adverse Effects (6) : Isoniazid

Answer 7

(1) Vitamin B6 Excretion
(2) ⇒ Peripheral neuropathy
(3) Seizures
(4) Hepatotoxicity
(5) Drug-induced lupus
(6) Inhibits CYP450
* (INH = Injury to Nerves and Hepatocytes)*
* (Note: All antimycobacterial agents can cause hepatotoxicity)*

Question 8

Which antimycobacterial agent is metabolized by the liver enzyme N-acetyltransferase?

Answer 8

Isoniazid

(Slow acetylators ⇒ ↑ [INH]. There is a similar relationship with Procainamide, acetylation rates, and drug-induced lupus)

Question 9

How do you prevent Isoniazid induced peripheral neuropathy?

Answer 9

Co-administer Vitamin B6

Question 10

What abnormal lab value is expected after administering Isoniazid?

Answer 10

Increased aminotransferases

(Asymptomatic)

Question 11

Which antimycobacterial drug can cause anion gap metabolic acidosis?

Answer 11

Isoniazid

Question 12

Which antimycobacterial agent is a potent inducer of CYP450?

Answer 12

Rifampin

(Compared to Isoniazid which inhibits CYP450)

Question 13

MOA: Rifampin

Answer 13

Inhibits DNA-dependent-RNA polymerase

Question 14

When can Rifampin be used as a monotherapy?

Answer 14

PROPHYLAXIS for those exposed to:

(1) Neisseria meningitis
(2) Haemophilus influenzae
* (Otherwise, organisms quickly develop resistance)*

Question 15

Which drug can turn bodily fluids orange?

Answer 15

Rifampin

Question 16

MOA: Ethambutol

Answer 16

Inhibits arabinosyl transferase ⇒ inhibits carbohydrate polymerization

(“Think Ethambutol at the cell wall”)

Question 17

Is Ethambutol bacteriostatic or bacteriocidal?

Answer 17

Bacteriostatic

Question 18

Adverse Effect: Ethambutol

Answer 18

Optic neuritis

(Including red-green color blindness)

Question 19

Which antimycobacterial agent may precipitate gout attacks?

Answer 19

Pyrazinamide

Question 20

Which mycobacterial species constitute the Mycobacterium avium complex?

Answer 20

(1) Mycobacterium avium
(2) Mycobacterium intracellulare

Question 21

Treatment: Mycobacterium avium complex

Answer 21

(1) Macrolide
(2) + Ethambutol
* (Rifabutin can be added as a third agent as well)*

Question 22

CD4 count allowing: Mycobacterium avium complex

Answer 22

CD4 < 50

Question 23

When treating tuberculosis in an HIV patient, what drug is used in place of Rifampin?

Answer 23

Rifabutin

(∵ It’s a weaker inducer of CYP450)

Question 24

Reservoir: Mycobacterium leprae

Answer 24

Armadillo

Question 25

Adverse Effects (2) : Dapsone

Answer 25

(1) Agranulocytosis
(2) Oxidative stress ⇒ Hemolytic anemia
* (Anemia in G6PD deficient individuals. Although not mentioned in the sketch, Dapsone is a Sulfa drug)*

Question 26

What drug is only used during the treatment of lepromatous leprosy?

Answer 26

Clofazimine

Question 27

Treatment: M. leprae

Answer 27

(1) Dapsone
(2) Clofazimine
(3) Rifampin
* (Clofazimine use only for the lepromatous form. Rifampin added for longterm therapy)*