Folic Acid Synthesis Inhibitors

Question 1

Sulfonamides

Answer 1

Drugs: “sulf” drugs

MOA: competes with PABA at 1st step of folic acid pathway

Question 2

Sulfonamide: Pharmacokinetics

Answer 2

High risk of drug interactions: drug is highly protein bound, thus may displace other drugs from binding plasma proteins, increasing toxicity (ex. warfarin)

Do not take if pregnant
Drugs displace bilirubin from protein binding sites in neonates

Question 3

Sulfonamide Resistance Mechanisms

Answer 3

Bacteria reduce uptake of drug
Bacteria finds alternate pathways to produce folic acid
Produce excessive amounts of PABA to compete with sulfonamides
Alter the enzyme that catalyzes the rate limiting step of folic acid synthesis

Question 4

Trimethoprim

Answer 4

MOA: inhibits dihydrofolate reductase