Can you explain why people with poor kidney function are at risk for problems with toxicity?
If the medication has been metabolized by the liver before excretion, isn't the medication mostly (or completely) inactive?
Thank you for your reply.
To understand the effect of kidney impairment on drug toxicity, it can be helpful to think of drug metabolism and excretion as a two step process. The first step takes place in the liver where drugs are metabolized and the second step takes place in the kidney where drugs are eliminated from the body in urine. Not all drugs are ready to be eliminated through the kidneys in their natural state. The liver prepares drug molecules for elimination; these are called metabolites.
There is some variability to this: some drugs are metabolized in different tissues (other than the liver), and some drugs are eliminated through the gut along with waste products or feces (and not through the kidneys in urine). Lastly, some drugs have more active metabolites than other drugs do, and not all drugs are inactive after liver metabolism.
If someone has poor kidney function, the drug metabolites may begin to accumulate, as the body cannot eliminate them properly. Again, there is a lot of variables in this process, but this is essentially why drug toxicity is a concern with kidney impairment.
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