Antimicrobials - Antimetabolites Flashcards
How do sulfonamides work?
Compete with PABA to bind and inhibit dihydropteroate synthetase, the first step in making DNA
How does trimethoprim work?
Inhibits dihydrofolate reductase which stops the formation of THF acid and DNA
What is the bacterial spectrum of the folic acid synthesis inhibitors?
- S. aureus
- G- rods (E. coli, Klebsiella)
- Parasites: Pneumocysitis and Toxoplasmosis
- used for uncomplicated UTIs, Pneumocystis pneumonia, Toxoplasmosis
What are the adverse effects of trimethoprim/sulfamethoxazole?
- allergy (sulfa component)
- hyperkalemia in the context of renal insufficiency
- hemolytic anemia in G6PD
What vitamin does Mycobacterium tuberculosis use to a much greater extent than humans, allowing it to be a target of antimicrobial therapy?
pyridoxine
What is the mechanism of isoniazid?
- inhibits mycolic acid synthesis
- high level of resistance due to slow growth, calling for use of other drugs in antitubercular regimen
How do rifampin, pyrazinamide, and ethambutol work?
Rifampin: nucleic acid synthesis inhibitor
Pyrazinamide: decreases energy
Ethambutol: inhibits synthesis of cell wall component arabingalactan
Which antituberculars are associated with centrilobular hepatitis?
- isoniazid
- pyrazinamide
- rifampin
Isoniazid has a toxic intermediate that can cause what side effects? What do you co-administer to prevent?
SEs: peripheral neuropathy, sideroblastic anemia, status epilepticus
Co-administer pyridoxine (Vit B6)
Besides hepatitis, what is another side effect of pyrazinamide?
- hyperuricemia, precipitation of gout
What is the major side effect of ethambutol?
- causes dose-dependent optic neuritis (decreased visual acuity and loss of red-green discrimination)
