Debate resolved: there are differential effects of serotonin selective reuptake inhibitors on cytochrome P450 enzymes.

In 1993, it was first proposed that an important difference between selective serotonin reuptake inhibitors (SSRIs) was the degree of inhibition of the cytochrome P450 (CYP) enzyme 2D6 that they produced under usually dosing conditions (Preskorn, 1993). Specifically, fluoxetine and paroxetine, in contrast to sertraline, were identified as causing substantial increases in the plasma levels of coadministered drugs, which were principally dependent on CYP 2D6 for their metabolism. Over the next 5 years, this position was hotly contested (Preskorn and Nemeroff, 1997). However, an extensive body of research has now accumulated, which incontrovertibly supports the original position. This paper will reviews this research and extends the discussion to all five SSRIs and four other important CYP enzymes: 1A2, 2C9/10, 2C19, and 3A3/4.