antimetabolites

Question 1

agents

Answer 1

trimethoprim-sulfamethoxazole (bactrim)

Question 2

mechanism

Answer 2

sulfa: interferes with bacterial folic acid metabolism via inhibition of DHFA reduction from PABA
trimetho: inhibits DHFA reduction resulting in sequential inhibition of enzymes of the folic acid path

Question 3

resistance

Answer 3

lower affinity of dihydropteroate sythesis for sulfonamides. decreased bacterial permeability or active efflux, alternative metabolic path for synthesis, increased production essential metabolite.

Question 4

spectrum

Answer 4

positive: MRSA/MSSA, s. pneumoniae, listeria. negative: enterobacter (ecoli, klebsiella, enterobacter), stenotrophomonas (DOC). toxo, nocardia, pneumocystis,

Question 5

does this work on anaerobes

Answer 5

no

Question 6

clinical

Answer 6

pneumocystis jirovecii, toxo encephalitis, UTI, listeria meningitis, MRSA.

Question 7

adverse

Answer 7

rash (SJS, TEN), bone marrow suppression, renal (pseudofailure, AIN, hyperkalemia)

Question 8

what is unique about trimeth-sulfa with the kidney

Answer 8

it acts as a K+ sparing diuretic.

Question 9

interactions

Answer 9

inhibition of CYP2C9 affects warfarin leading to increase in the INR