Chem Basis - Penicillins 3

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  1. Acylating the side chain amino group of 6-aminopenicillinic acid with several acids can produce a wide range of synthetic penicillin products with what varying characteristics?
    Image Upload 1Antimicrobial activity, Acid/oral stability, Pharmacokinetic profile, GI absorption, Side effects and DDIs
  2. How can a penicillin be altered to become a prodrug?
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    • Make the C3-COOH an ester
  3. What is the advantage of creating an ester prodrug from a penicillin?
    Increased oral bioavailability in acid stable compounds
  4. What is the preferred route of Penicillin administration for serious systemic infections?
  5. What is the advantage of an inorganic salt at the C3-COOH of a penicillin?
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    Can be given IV, Rapid oral absorption
  6. What are disadvantages of inorganic salt forms of Penicillin?
    K type may cause problems for patients with: Arrhythmias or hyperkalemia, Na type may cause problems for patients with hypertension or heart failure
  7. Why is Carbenicillin not a good choice for patients with Hypertension of heart failure?
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    • Contains a Disodium salt, creating a higher potential for problems than other salt forms
  8. Benzathine and Procaine are penicillin salts are water insoluble, why?
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    • Because of the large organic counter ion
  9. By what route and in what type of formulation can benzathine and procaine penicillin salts be given?
    IM, formulated in depo preparations (oils)
  10. What is the advantage of benzathine and procaine Penicillins salts given in an oil based depo IM injection?
    Slow release over a long period of time, improving patient compliance since one single injection may be sufficient and uniform prolonged blood levels, enhancing effectiveness
  11. (True/False) The C3-COOH forms water soluble and water insoluble salts.
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  12. (True/False) The C3-COOH can form water soluble salts that include sodium and potassium salts which cannot be given intravenously.
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    False, can be given intravenously
  13. (True/False) Sodium salts of the C3-COOH of some penicillin preparations are contraindicated in patients with heart failure.
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  14. (True/False) Water insoluble salts of the C3-COOH have a long duration of action and should be given intramuscularly.
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  15. The naturally occurring penicillin G contains what side chain?
    Benzyl groupImage Upload 10
  16. Pen G has good or bad oral activity and why?
    Poor oral activity, because it is acid liable
  17. In what way can you enhance the oral activity of Pen G?
    Give with antacid to increase gastric pH > 3 (Decreases protonation of the beta lactam N which starts the acid degradation pathway)
  18. How does the spectrum of Pen G compare to Pen V?
  19. Which has oral activity, Pen V or Pen G and why?
    Pen V, because the O in the side chain reduces the nucleophilic character of the side chain carbonyl O, inhibiting acidic degredation
  20. Which is Pen V effective for the treatment of G+ infections and why?
    The Phenoxy group, b/c it is lipophilic

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  21. Will bulking up the R group of a Penicillin prevent hydrolysis by B-lactamases?
  22. Why is Methicillin is reserved as a last resort?
    To prevent the development of resistance
  23. What drugs discussed in the B-lactam section are used for MRSA?
    Linizold and Daptomycin
  24. What type of bacteria is Linezolid effective against?
    Aerobic G+
  25. Why is there no cross resistance between Linezolid, Penicillins and Cephalosporins?
    The MOA is different
  26. What is the MOA for Linezolid?
    Binds to the bacterial 23s ribosomal RNA of the 50S subunit resulting in inhibition of translation, protein, DNA and RNA synthesis.
  27. Which B-lactams have an amino group on the C-alpha?
    • Ampicillin an Amoxicillin
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  28. There is a saturated derivative of ampicillin called Cyclacillin which is identical to ampicillin in antimicrobial coverage, what is the benefit of using it over ampicillin?
    It has some resistance to beta lactamases since the Cα is in a ring (causing steric hindrance to attack) AND faster/ more complete oral absorption with less allergic reaction
  29. Why is amoxicillin dosed q8h compared to q6h for ampicillin?
    • Amoxicillin’s para OH group enhances absorption and blood levels
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  30. Why does Amoxacillin have a lower incidence of GI disturbances compared to Ampacillin?
    • Amoxicillin’s para OH group enhances absorption
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  31. In what ways can you increase the absorption and decrease the diarrhea side effects of a B-lactam?
    Form an ester prodrug from the carboxylic group (esters are not zwitterion), increasing lipophilicity and increasing absorption
  32. Would you expect an ester prodrug B-lactam (ester at C3–COOH) to be dosed more or less frequently?
  33. Adding polar functional group to Cα broadens spectrum, why?
    The drug is now able to penetrate through polar channels in G- cell wall
  34. Adding polar functional group to Cα broadens the G- spectrum, what effect does it have on the G+ spectrum?
    Narrow G+ spectrum
  35. What two functional groups on marketed products enhance the spectrum?
    Amino group of (e.g.ampicillin) and the carboxylic group of (e.g. carbenicillin) Image Upload 15
  36. Why is Carbacilillin rarely used against Pseudomonas?
    Relatively poor activity and large doses are required
  37. (True/False) Marketed products with -COOH on the alpha carbon are acid-stable.
    False, acid-labile
Card Set
Chem Basis - Penicillins 3
Chem Basis - Penicillins 3
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