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Flashcards in Antibiotics V Deck (20)
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1


What are the two bacterial antimetabolites?

 

  1. Folic Acid trimethoprim/sulfamethoxazole
  2. Antituberculars (Isoniazid, pyrazinamide, ethambutol)

2


What is the strategy for AB antimetabolite Tx?


Bacteria need to synthesize folic acid (as opposed to humans which ingest folic acid)

3


What do bacteria use to make folic acid?


Para-aminobenzoicacid

4


What drugs inhibit Dihydropteroate synthetase and compete with para-aminobenzoicacid?


Sulfonamides

5

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)

6


What are the typical clinical uses of folic acid antimetabolites?

 

  • Uncomplicated UTIs
  • Pneumocystis pneumonia (Tx and prophylaxis)
  • Toxoplasmosis infection

7

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)

8


What is the general strategy to treat tuberculosis?


TB utilizes pyridoxine to a much greater extent than human cells - therefore, use antimetabolites!

9


What drug regimen must be used for infection with TB?


ONLY a 9 month isoniazid

10


What drug regimen must be used to treat an active infection of TB?


Four drugs:

  1. Isoniazid
  2. Rifampin
  3. Ethambutol
  4. Pyrazinamide

11


Why is a long duration of isoniazid needed?


TB has a notoriously slow growing life cycle

12


How does rifampin work to block TB growth?


Nucleic acid synthesis inhibitor

13

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

14


What is the term used to treat asymptomatic infection of TB?


Chemoprophylaxis

15

What is the rationale for agressive, potentially toxic Tx of TB?

  • Active disease will always disseminate unless treated
  • Public health considerations

16


What are the three anti TB drugs associated with centrolobular hepatitis?


Isoniazid, pyrazinamide, rifampin

17


What is administered with rifampin to minimize peripheral neuropathy?


B6 (pyridoxine)

18


What side effects are observed that are unique to rifampin?

 

  • Serious flu-like hyper-sensitivity syndrome characterized by fever, myalgias, interstitial nephritis, thrombocytopenia, hemolytic anemia

19


What SEs are are unique to Pyrazinamide?

 

  • Increased uric acid levels and precipitation of gout

20


What are the side effects specific to Ethambutol?


Causes dose-dependent optic neuritis, manifested by loss of ability to differentiate red and green

Elevates uric acid levels and predisposes to gout