Psychotropic medications that are not metabolized (mostly excreted unchanged)

Some psychotropic medications are not metabolized or minimally metabolized. They are entirely or predominantly excreted unchanged. Why should we care? To the extent that a medication is not metabolized, their pharmacokinetics is not affected by cytochrome-P450-based drug interactions or by liver disease. On the other hand, to the extent that a medication is excreted unchanged by…