TB drugs

Question 1

TB- symptoms

Answer 1

• fever
• fatigue
• chest pain
• haemoptysis

Question 2

TB- definitive diagnosis

Answer 2

• abnormal chest radiograph
• positive tuberculin skin test
• positive sputum culture or smear

Question 3

TB- first line drugs

Answer 3

isoniazid
rifampicin
rifabutin
pyrazinamide
ethambutol
streptomycin

Question 4

Isoniazid- MOA

Answer 4

activated into active form by catalase peroxidase
inhibit enoyl-acyl carrier protein reductase, which is an important component of FASII
innhibit long chain mycolic acid synthesis, which is component of cell wall

• acetylation by liver N- acetyltransferase -> inactive

Question 5

Isoniazid- properties

Answer 5

• oral and IV
• intracellular and extracellular

side effects: peripheral neuropathy (corrected by pyridoxine intake)
liver toxicity
GI disturbances

Question 6

Rifampicin- MOA

Answer 6

• bind to beta subunit of RNA polymerase and inhibit mRNA transcription
• inhibit protein synthesis -> produce non-functional proteins

Question 7

Rifampicin- properties

Answer 7

• oral and IV
• intracellular and extracellular

side effects:
harmless orange-red disclouration of body secretions
hepatitis
induces liver drug metabolising enzymes

Question 8

Rifabutin- MOA

Answer 8

same as rifampicin

Question 9

Rifabutin- properties

Answer 9

• intracellular and extracellular
  long serum half life of 45 hours
• reduce the induction of drug metabolizing enzymes
• anti-HIV drug interaction reduces, suitable for HIV patients

Question 10

Ethambutol- MOA

Answer 10

• inhibit arabinose transferase, and thus the synthesis of arabinogalactan
• which is an important component of cell wall

Question 11

Ethambutol- properties

Answer 11

• intracellular and extracellular

- optic neuritis (monitor the visual acuity and avoid children less than 5 yo)

Question 12

Pyrazinamide- MOA

Answer 12

• activated into pyrazinoic acid by pyrazinamase
• inhibit the FAS-1
• inhibit short chain mycolic acid syntheis

Question 13

Pyrazinamide- properties

Answer 13

• more useful against intracellular TB

- GI disturbances and hepatotoxicity

Question 14

Streptomycin- MOA

Answer 14

• binds to 30s subunit of ribosome and causes codon misreading, inhibit protein synthesis

Question 15

Streptomycin- properties

Answer 15

• more useful against extracellular TB, cannot well penetrate into macrophage or lesion
• side effect: hearing loss
  IM injection