Psychiatric drugs are often metabolized by liver enzymes. Multiple drugs may utilize the same enzyme, causing drug interactions, or normal variability in these enzymes may affect ability to metabolize specific drugs.
This go-to reference indicates potential drug interactions resulting from competition for, or effects on the human cytochrome P450 system, a way to identify the liver enzymes.
Flockhart DA. Drug Interactions: Cytochrome P450 Drug Interaction Table. Indiana University Schoo