The previous discussion examined the effect of changing each pharmacokinetic parameter individually on the drug and metabolite plasma profiles after a single iv dose of the parent drug.
Changing one of the drug/metabolite pharmacokinetic parameters will be accompanied most of the time with a change in some other parameters.
- A decrease in the function of one of the drug eliminating organs results in lower drug , and slower rate of drug elimination (if vd is not affected).
- This will change the relative magnitude of the different organ clearances, leading to a change in and a change in the amount of metabolite formed in vivo.
- If the organ with the decreased function is involved in metabolite elimination, the will also be lower.
- Individuals can metabolize the drugs at different rates due to their genetic phenotypes. For example slow and rapid acetylators acetylate drugs at significantly different rates.
- This will change the relative magnitude for the individual organ clearances, leading to a change in and a change in the amount of metabolite formed in vivo.
- Metabolite elimination will be affected only if the genetically different process is involved in metabolite elimination.
Individuals with different body weight usually have different for the same drug.
This difference in drug will be accompanied by a similar difference in the metabolite volume of distribution.
