- What two pharmacokinetic constants account for the differences between Na ampicillin and ampicillin trihydrate given intramuscularly?
Low Ka and F are the result of slower and less complete absorption of ampicillin trihydrate.
- If the pharmacokinetic model is dose independent (as implied in this module and the associated worksheet), doubling the dose (same interval) should double the steady state concentrations. It is actually quite likely that the absorption kinetics of ampicillin trihydrate are dose dependent. If this is so, doubling the dose should produce
- more than a doubling of the steady state concentrations.
- less than a doubling of steady state concentrations.
This answer is true and consistent for dose-dependent ABSORPTION (any drug) and the opposite for dose-dependent ELIMINATION.
- A clinical patient of yours has received several doses of IV Ampicillin sodium (for a suspected gram negative infection) and appears to be responding. Your technician informs you that "no more veins are available". Do you choose IM Ampicillin sodium (#2) or IM Ampicillin trihydrate (#3) to acheive the SAME clinical effect?
Intramuscular sodium ampicillin comes much closer than ampicillin trihydrate to produce the same concentration profile as intravenous sodium ampicillin. Clinical effects (e.g. cidal antibacterial activity) should also be more similar.
- Based on your answer for question 3, do you need to give a larger total dose or can it remain approximately the same?
BASED ON THE MODEL DESCRIBED IN THIS EXERCISE dosage can remain approximately the same.