Module 5 questions - Species differences (Clinical challenge)
  1. Based on the information presented in this module does it appear that chloramphenicol can be given to cats in a way that is as effective, as safe and as practical as it is given to dogs?

    No it does not. It should be clear from this exercise that identical plasma concentration profiles cannot be produced in cats and dogs. It should be possible to produce a dosage regimen for chloramphenicol in cats that remains below the toxic level and above the effective level. If the assertion that toxicity is not related ONLY to exceding some "maximum" concentration, it is unlikely that such a regimen would be safe (for cats).

  2. This quote appears in the USP monograph for Chloramphenicol: "Doses of 25 to 50 mg per kg of body weight every twelve hours have been recommended, and may be necessary for some infections, but could increase the risk of side effects". In terms of the plasma concentration vs time profile, why might 50 mg/kg be a more effective dose?

    The higher concentrations are more likely to exceed the MIC of any given bacteria than are lower concentrations.

  3. Based on the same USP quote in question 2 and in terms of the plasma concentration vs time profile, why might 50 mg/kg be a more toxic dose?

    50 mg/kg q12H produces a concentraiton profile in cats that exceeds the toxic concentration. Cave and Cmin concentrations are still elevated as compared to dogs. Based on pharmacokinetics alone, a higher incidence of toxicity (in cats) seems likely.