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Flashcards in Antimycobacterial Drugs Deck (21):
0

What is the mechanism of action of isoniazid (INH)?

1. Requires bioactivation.
2. Inhibits mycolic acid synthesis.
3. Resistance vie expression of katG and
inhA genes.

1

What is the clinical use of isoniazid?

1. Bactericidal
2. Primary drug for latent TB infection and a primary drug for use in combination.

2

What are the pharmacokinetics of isoniazid?

1. Oral and IV forms
2. Hepatic clearance (fast and slow acetylators)
3. Inhibits metabolism of carbamazepine + phenytoin + warfarin.

3

What is the toxicity of isoniazid?

1. Hepatotoxicity
2. Peripheral neuropathy (use pyridoxine)
3. Hemolysis in G6PD deficiency

4

What are the three main rifamycins?

1. Rifampin (RIF)
2. Rifabutin
3. Rifapentine

5

What is the mechanism of action of rifamycins?

Inhibit DNA-dependent RNA polymerase.
Resistance emerges rapidly when drug is used alone.

6

What is the clinical use of rifamycins?

1. Bactericidal
2. RIF is an optional drug for latent TB infection.
3. A primary drug used in combinations for active TB.

7

What are the pharmacokinetics of rifamycins?

1. Rifampin --> oral/ IV
2. Others oral.
3. Enterohepatic cycling with some metabolism.
4. Induced formation of CYP450 by RIF leads to decreased efficacy of many drugs (rifabutin less).

8

What are the possible toxicities of rifamycins?

1. Rash
2. Nephritis
3. Cholestasis
4. Thrombocytopenia
5. Flu-like syndrome with intermittent dosing

9

What is the mechanism of action of ethambutol?

Inhibits formation of arabinoglycan - a component of mycobacterial cell wall.
Resistance emerges rapidly if drug is used alone.

10

What is the clinical use of ethambutol?

1. Bacteriostatic
2. Component of many drug combination regimens for active TB

11

What are the pharmacokinetics of ethambutol?

1. Oral administration
2. Renal elimination with large fraction unchanged
3. Reduce dose in renal dysfunction

12

What are the toxicities of ethambutol?

1. Dose dependent visual disturbances, reversible on discontinuance.
2. Headache and confusion
3. Hyperuricemia
4. Peripheral neuritis

13

What is the mechanism of action of pyrazinamide?

Uncertain - requires activation via hydrolytic enzymes to form pyrazoic acid (active).

14

What is the clinical use of pyrazinamide?

Bacteriostatic - component of many drug combination regimens for active TB.

15

What are the pharmacokinetics of pyrazinamide?

1. Oral administered
2. Both hepatic and renal elimination (reduce dose in dysfunction)

16

What are the toxicities of pyrazinamide?

1. Polyarthralgia (40%)
2. Hyperuricemia
3. Myalgia
4. Maculopapular rash
5. Porphyria
6. Photosensitivity
7. Avoid in pregnancy

17

What is the mechanism of action of streptomycin?

Binds to S12 ribosomal subunit inhibiting protein synthesis.

18

What is the clinical use of streptomycin?

1. Bactericidal
2. Used in TB when injectable drug needed.
3. In treatment of drug-resistant strains.

19

What are the pharmacokinetics of streptomycin?

Parenteral administration and renal elimination.

20

What is the toxicity of streptomycin?

Ototoxicity and Nephrotoxicity

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