Anti-TB Flashcards
metabolism and excretion of rifampicin
liver; bile
the adverse effect of rifampicin
cutaneous rxn: pruritis, flush
flu-like symptoms: fever, chills
hepatitis
orange discoloration of bodily fluids: tears, sweat, urine
DDI of rifampicin (which CYP)
cyp450 inducer: decrease levels of warfarin, CS, hormonal contraceptives, HIV protease inhibitors
CNS penetration of rifampicin
10-20%
How does resistance to rifampicin is acquired?
mutations in gene, encoding the RNA polymerase beta chain
How does resistance to isoniazid is acquired?
mutations to catalase-oxidase enzymes converting isoniazid, regulatory genes of the mycolic acid synthesis
which is the toxic and non-toxic metabolite formed via the amidase and NAT2 pathway respectively?
hydrazine; acetyl hydrazine
why is pyridoxine given along with isoniazid
isoniazid competitively inhibits pyridoxal phosphate formation (active form of it B6) -> causes peripheral neuropathy
which two anti-TB drugs should be given 2 hours spaced apart from antacids?
isoniazid (delay absorption) and ethambutol (decreases level of E)
adverse effect of isoniazid?
peripheral neuropathy, GI effects, hepatitis
DDI of isoniazid
CYP450 inhibitor: increase phenytoin and carbamazepine
which drug allows the TB treatment to become 6 months? also the most effective drug
Pyrazinamide
MOA of pyrazinamide
converted into pyrazinoic acid by pyrazinamidase -> decrease intracellular pH
adverse effects of pyrazinamide?
Hepatotoxicity (higher risk when + Isoniazid)
Hyperuricaemia and arthralgia
GI effects: N/V
Photosensitivity
Exanthema (widespread rashes) and pruritis
How does resistance to pyrazinamide occur?
mutation to the gene encoding, pyrazinamidase enzyme
How does resistance to ethambutol occur?
mutation to embB gene
adverse effect of ethambutol
visual toxicity (higher risk if kidney failure and elderly)
- toxicity is dose-dependent
- monitoring for young required
hyperuricemia/gout
what is MDR in TB treatment?
resistant to first line anti-TB, esp rifampicin and isoniazid
treatment requires second line anti-TB drugs (more toxic and $$)
what is XDR in TB treatment
resistant to second line: FQ and injectables
what is cure
negative sputum in the last month of treatment
what is treatment failure
positive sputum at or after 5months of treatment
what is a good marker to indicate risk of relapse
nonconversion of sputum culture at 2 months
Which anti-TB drugs have GI sx such as nausea, anorexia, abdominal discomfort
RIP
Which anti-TB drugs have cutaenous rxns which are usually self-limiting (pruritus)?
RIPE (all first anti-TB drug)
