TB

Question 1

First line TB drugs: ? Cidal or static

? Main side effects

Answer 1

Isoniazid: cidal (against intra and extra cellular org). Hepatitis, periph neuropathy (use pyridoxine), hypersensitivity reactions.

Rifampicin: cidal against intra and extra cellular. Interactions++(warfarin, OCP, corticosteroids, hypoglycaemics), hepatitis, hypersens

Ethambutol: static. Optic neuritis (assess VA and colour vision)

Pyrazinamide: intra cellular (most active first 2months). Arthralgia from hyperuricaemia, hepatitis, hypersensitivity reactions.

Question 2

Hallmarks of LTBI?

Answer 2

Reactive TST and absent clinical and radio graphical manifestations

Question 3

What is the risk of infants with LTBI developing into tuberculosis? What is the adult lifetime risk? When are they most at risk of this?

Answer 3

40%. 5-10%. Most at risk of progression in the first 2 years.

Question 4

Mechanism of action of isoniazid?

Answer 4

Reduced synthesis of mycolic acids needed in AFB cell wall. Cidal against dividing AFB, static for resting AFB.
CSF reached same as serum conc

Question 5

Mechanism of action of rifampicin?

Answer 5

Inhibits DNA Dep RNA polymerase = bacteriocidal

CSF reaches 10-40%of serum

Question 6

How long does it take for a mantoux to become positive after primary infection?
?%of children who do not initially react to mantoux

Answer 6

2-10weeks

10-40%