Tuberculosis

Question 1

Describe the 1st line Rx regimen for TB?

Answer 1

1st line treatment: 
- use 3-4 drugs for 2 months (RIPE P mnemonic)
- then Isonizid and Rifampicin continued another 6 months (9 months if meningitis or HIV)
•	Rifampicin
•	Isoniazid
•	Pyrazinamide
•	Ethambutol
•	Pyridoxine

Question 2

Describe the 2nd line Rx for TB?

Answer 2

2nd line treatment: if tolerance or resistance
• Steptomycin
• Capreomycin
• Cycloserine

Question 3

Describe the MA and SE of Rifampicin?

Answer 3

Rifampicin (1st line)
o MA: inhibits RNA synthesis of prokaryotic cells
- resistance develops rapidly 
o Spectrum: most gram negative bacteria 
o Metabolism: hepatic 
o SE: N/V, diarrhoea, rash, fever

Question 4

Describe the MA and SE of Isoniazid?

Answer 4

Isoniazid (1st line)
o MA: blocks arabinosyl transferase -> inhibits synthesis of arabinogalactan component of mycobacterial cell wall
o Used as chemoprophylaxis in high risk groups (exposed, positive TST in HIV pt, inactive TB)
o SE: allergic skin reactions, vit B6 deficiency, peripheral neuropathy

Question 5

Describe the MA and SE of Pyrazinamide?

Answer 5

Pyrazinamide (1st line)
o MA: converted to pyrazinoid acid by mycobacterial pyrazinamidase -> disrupts cell membrane transport, fatty acid synthesis and cell wall synthesis
- inactive at neutral pH but bacteriacidal in acidic conditions -> effective against bacteria inside macrophages
o SE: gout, GIT discomfort, liver damage (high dose)

Question 6

Describe the MA and SE of Ethambutol?

Answer 6

Ethambutol (1st line)
o MA: inhibits cell wall synthesis
- rapid resistance development
o Spectrum: only affects mycobacteria
o Metabolism: renally excreted, can cause liver damage
o SE: uncommon, optic neuritis, peripheral neuropathy

Question 7

Describe the MA and indication of Pyridoxine?

Answer 7

Pyridoxine (1st line supplement)
o MA: Vit B6
o Indication: treat Vit B6 deficiency caused by isoniazid -> prevent peripheral neuropathy

Question 8

Describe the MA and SE of Streptomycin?

Answer 8

Streptomycin
o Class: Aminoglycoside
o MA: binds to 30S ribosomal subunit -> inhibits protein synthesis
o SE: ototoxicity, nephrotoxicity, electrolyte disturbance, fever, rash, hypersensitivity, anaphylaxis

Question 9

Describe the MA and SE of Capreomycin?

Answer 9

Capreomycin
o Class: cyclic peptide
o MA: inhibits protein synthesis
o SE: hypokalaemia, hypomganesaemia, ototoxicity, renal toxicity

Question 10

Describe the MA and SE of Cycloserine?

Answer 10

Cycloserine
o Class: alanine anologue
o MA: inhibits cell wall synthesis
o SE: neurological and psychologic disturbances