L53 Anti-tuberculosis drugs

Question 1

MOA of rifampicin?

- Dosing 600mg

Answer 1

DNA-dependent RNA polymerase inhibitor

Question 2

What cautions to pay attention to when given rifampicin?

Answer 2

1. Color body fluid red-orange

2. Resistance: rpoB mutants of MTB

Question 3

List 3 S/E of rifampicin.

Answer 3

1. Rash
2. Hepatitis esp. DDI (combined oral contraceptives, protease inhibitors)
3. DDI

Question 4

MOA of isoniazid 300mg?

Answer 4

Inhibit cell wall synthesis by inhibiting mycolic acid synthesis

Question 5

Other than rash and hepatitis, S/E of isoniazid? (2) How to prevent one of the S/E?

Answer 5

1. DDI: phenytoin (isoniazid reduced clearance of phenytoin)
2. Peripheral neuropathy
   - prevented by supplying with B6 (as it is an antimetabolite of pyridoxine)

Question 6

Why Isoniazid is not recommended to be given alone?

Answer 6

Resistance develops rapidly if given alone.

Question 7

What are the side effects of pyrazinamide (1-2g)? (3)

Answer 7

1. Hepatitis (MC!)
2. Gout
3. Arthralgia

Question 8

MOA of ethambutol (800mg)?

Answer 8

Inhibit cell wall synthesis by inhibiting arabinogalactan synthesis.

Question 9

What is the most distinctive S/E of ethambutol?

- Rash is a side effect.

Answer 9

Retrobulbar neuritis (a form of optic neuritis)

• maybe unilateral neuritis, document visual acuity before the treatment!

Question 10

Other than RIPE, 1g of _______ can be given to irreversibly inhibit 30S ribosome subunit.

Answer 10

Streptomycin (an aminoglycoside)

Question 11

What is the route of administration of streptomycin? What are the 2 side effects?

Answer 11

• IM route

1. Ototoxicity
2. Renal toxicity

Question 12

What can be used as a replacement drug for rifampicin and isoniazid for patients with deranged LFT/ MDR/ XDR-TB? (2)

MOA? (1)

Answer 12

Quinolones

1. Levofloxacin
2. Moxifloxacin

• they work by inhibiting DNA gyrase

Question 13

Why is Dapsone used for? It is an anti-folate.

Methemoglobinemia as a side effect!

Answer 13

Treatment for leprosy with rifampicin and clofazimine

Question 14

1st line drug for MTB is RIPE, what are the 2nd line drugs?

Answer 14

1. Capreomycin
2. Kanamycin
3. Amikacin

Question 15

The treatment regime can be divided into the initial phase (2months) and a continuation phase (2 months). Briefly describe.

Answer 15

1. 4 1st line drugs, kill most bacteria

2. Continuation phase: Rifampicin + Isoniazid, kill remaining bacteria.

Question 16

What is measured as an indicator of drug efficacy after 1st few doses? It is particularly useful in anti-TB drugs.

Answer 16

EBA

Early bactericidal activity

Question 17

What has to be monitored after administrating TB drugs? (3)

• state what to be monitored and the related drug(s)

Answer 17

1. LFT: H,R,Z (MC Z)
2. Serum urate: Z
3. Visual acuity: E