Cytochrome P-450 monooxygenases and interactions of psychotropic drugs

The authors review drug biotransformation. Phase I reactions are preconjugation processes that take place through cytochrome P-450--a hepatic mixed function oxidase (MFO) enzyme system with multiple isozymes to metabolize foreign substances. Phase II reactions are conjugation processes of the substrates. Based on the characteristics of the cytochrome P-450 microsomal enzyme systems, the authors explain the clinical phenomena of induction and inhibition of these enzymes when psychotropic agents interact. This article describes both MFO inducers (barbiturates) and inhibitors (cimeditine, fluoxetine and neuroleptic drugs). With this information, clinicians can enhance the ability to monitor drug interactions of psychotropic agents.