Antibiotics V Flashcards
What are the two bacterial antimetabolites?
- Folic Acid trimethoprim/sulfamethoxazole
- Antituberculars (Isoniazid, pyrazinamide, ethambutol)
What is the strategy for AB antimetabolite Tx?
Bacteria need to synthesize folic acid (as opposed to humans which ingest folic acid)
What do bacteria use to make folic acid?
Para-aminobenzoicacid
What drugs inhibit Dihydropteroate synthetase and compete with para-aminobenzoicacid?
Sulfonamides
What is the spectrum of the folic acid inhibitors?
- Staphylococcus aureus (85% activity vs MRSA)
- Gram negative rods (E. coli, Klebsiella only)
- Pleomorphic Gram negatives (H. influenzae)
- Parasites (Pneumocystis and Toxoplasmosis)
What are the typical clinical uses of folic acid antimetabolites?
- Uncomplicated UTIs
- Pneumocystis pneumonia (Tx and prophylaxis)
- Toxoplasmosis infection
Adverse side effects for trimethoprim/sulfamethoxazole?
- Allergy
- Hyperkalemia in patients with severe renal insufficiency b/c trimethoprim is structurally analogous to triamterene (K+ sparind diuretic)
What is the general strategy to treat tuberculosis?
TB utilizes pyridoxine to a much greater extent than human cells - therefore, use antimetabolites!
What drug regimen must be used for infection with TB?
ONLY a 9 month isoniazid
What drug regimen must be used to treat an active infection of TB?
Four drugs:
- Isoniazid
- Rifampin
- Ethambutol
- Pyrazinamide
Why is a long duration of isoniazid needed?
TB has a notoriously slow growing life cycle
How does rifampin work to block TB growth?
Nucleic acid synthesis inhibitor
What is the MOA of ethambutol?
Blocks arabinosyl transferase which catalyzes the synthesis of the amine sugar arabinogalactan used to make the mycobacterial cell wall
What is the term used to treat asymptomatic infection of TB?
Chemoprophylaxis
What is the rationale for agressive, potentially toxic Tx of TB?
- Active disease will always disseminate unless treated
- Public health considerations
