Pharmacology Exam II

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Rx2013
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65358
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Pharmacology Exam II
Updated:
2011-02-09 18:26:01
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Aminoglycosides
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Aminoglycosides
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  1. Aminoglycosides
    bactericidal inhibitors of protein synthesis
  2. Aminoglycoside drugs
    • streptomycin
    • neomycin
    • kanamycin
    • amikacin
    • gentamicin
    • tobramycin
    • sisomicin
    • netilmicin
  3. Aminoglycosides are used most widely against
    • gram-negative enteric bacteria
    • bacteremia
    • sepsis
    • endocarditis
    • tuberculosis
  4. Stability of aminoglycosides
    • water soluble
    • stable in solution
    • more active at alkaline pH
  5. Mechanism of action of aminoglycosides
    • irreversible inhibition of protein synthesis
    • passive diffusion across the outter membrane
    • active transport across the cell membrane
    • transport may be enhanced by PCN or vanc
  6. Aminoglycosides bind _____ inside the cell
    • 30s ribosomal subunit
    • some bind 50s
  7. 3 ways protein synthesis is inhibited by aminoglycosides
    • block initiation complex formation
    • interfere with the proofreading process, causing increased rate of errors in synthesis
    • inhibition of ribosomal translocation where the peptidyl-tRNA moves from the A site to the P site
  8. Initial site of aminoglycoside action
    • outer bacterial membrane
    • aminoglycoside creates fissures in the cell membrane
  9. 3 mechanisms of resistance to aminoglycosides
    • enzymes that inactivate the aminoglycoside
    • impaired entry of aminoglycosides into the cell
    • absence or alteration of the receptor on the 30s subunit
  10. Most common mechanism of resistance encountered by aminoglycosides
    enzymatic inactivation
  11. Oral absorption of aminoglycosides
    • very poor
    • only good if ulcerations are present
  12. Aminoglycoside bactericidal effects are based on
    • drug concentrations
    • increasing concentrations kill increasing proportions of bacteria
  13. Postantibiotic effect
    • antibacterial activity persists beyond the time which measureable drug concentrations are present
    • can last several hours with aminoglycosides
  14. Aminoglycosides in anaerobes
    • energy is needed for aminoglycoside uptake
    • less energy available in anaerobes
    • aminoglycoside = less effective in anaerobes
  15. Single daily doses are ______ when compared to multiple smaller doses through out the day.
    just as effective and no more toxic
  16. it is recommended that aminoglycosides be given
    once daily
  17. aminoglycosides must be dosed based on
    renal function
  18. aminoglycosides are cleared by the _____ and excretion is directly proportional to _______.
    • kidney
    • creatinine clearance
  19. Aminoglycoside distribution
    • highly polar compounds that do not enter cells readily
    • excluded from CNS and the eye
  20. Aminoglycoside dosing is based on
    renal function
  21. Manditory during aminoglycoside therapy
    monitoring of serum levels
  22. Aminoglycosides are used mostly against
    gram-negative enteric bacteria
  23. Aminoglycosides are almost always used in combination with
    • b-lactam antibiotics
    • extends coverage to gram + organisms
    • utilizes synergism
  24. PCN-aminoglycoside combo therapy is used in the treatment of
    • enterococcal endocarditis
    • shortens the duration of therapy for staph. endocarditis
  25. the lowest concentration of a drug in the blood between doses
    trough
  26. Adverse effects of aminoglycosides are ____ and ____ dependant
    • time
    • dose
  27. Toxicity is unlikely to occur with aminoglycosides until
    • a certain threshold concentration is met
    • 2 mcg/ml trough = toxicity
  28. All aminoglycosides exhibit this toxicity
    • ototoxic
    • nephrotoxic
  29. Aminoglycoside oto/nephrotoxicity are more likely to be encountered when
    • therapy is more than 5 days
    • high dosage is used
    • elderly pt
    • pt has renal insufficiency
  30. Use of aminoglycosides with ______ can potentiate nephrotoxicity.
    • loop diuretics
    • other nephrotoxic antimicrobials
  31. The most ototoxic aminoglycosides
    • neomycin
    • kanamycin
    • amikacin
  32. The most vestibulotoxic aminoglycosides
    • streptomycin
    • gentamicin
  33. the most nephrotoxic aminoglycosides
    • neomycin
    • tobramycin
    • gentamicin
  34. Streptomycin
    • similar activity as the aminoglycosides
    • same mechanisms of resistance
    • resistance limits the use of this drug
    • ribosomal resistance develops readily
  35. Streptomycin is mainly used as
    • a second line agent for treatment of tuberculosis
    • only in combo with other agents to prevent resistance
  36. Use of streptomycin in non-tuberculosis infections
    • plague, tularemia, brucellosis
    • in combo with oral TCN
  37. Streptomycin is useful in combo with PCN for the treatment of
    • enterococcal endocarditis
    • 2 week therapy for viridans strep. endocarditis
  38. Streptomycin alone may be used to treat
    enterococcal infections
  39. Adverse reactions of Streptomycin
    • hypersensitivity (rash, fever...)
    • usually in patients on long therapy
  40. the most serious toxic effect with streptomycin
    • disturbance of vestibular function (irreversible)
    • vertigo, loss of balance
    • porportional to age, blood levels and duration of therapy
    • can cause deafness in a newborn if given to mom
  41. Gentamycin spectrum
    gram - and gram +
  42. All aminoglycosides, including gentamicin have no activity against
    anaerobes
  43. Streptococci and enterococci are relatively resistant to gentamicin because
    gentamicin fails to penetrate into the cell
  44. Gentamicin uptake into the cells is greatly increased when administered with
    vancomycin
  45. Among gram-negative bacteria, resistance to gentamicin is most commonly due to
    aminoglycoside modifying enzymes
  46. Gentamicin is mainly used IV or IM for
    severe infections caused by gram - bacteria
  47. Gentamicin is used in combo with a second agent because
    an aminoglycoside alone my not be effective for infections outside the urinary tract
  48. Aminoglycosides are not used as single-agent therapy for pneumonia because
    • penetration of lung tissue is poor
    • local condition of low pH and low oxygen = poor activity
  49. Topical gentamicin is used for
    • infected burns, wounds or skin lesions
    • prevention of IV catheter infections
  50. Gentamicin ADRs
    • reversible mild nephrotoxicity (5-25% of pt receiving for 3-5 days)
    • irreversible ototoxicity (vestibular dysfunction)
    • loss of hearing could be possible
    • hypersensitivity is uncommon

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