A prospective antidepressant drug interaction surveillance program was established and collected data for over 4 years in Charleston, SC (Charleston Antidepressant Drug Interactions Surveillance Program, CADISP). One hundred and seventy patients were enrolled. The plasma concentrations and/or clinical effects of drug combinations were monitored in psychiatric patients who received therapy with a selective serotonin reuptake inhibitor (SSRI) or one of the other newer antidepressants (nefazodone, venlafaxine) when combined with other drugs metabolized by the cytochrome P-450 (CYP) enzyme system. Patient data were evaluated to estimate the occurrence and significance of antidepressant-induced metabolic drug interactions. Plasma drug concentrations in the presence and absence of treatment with an antidepressant served as the primary assessment variable. Contrary to the hypothesis that pharmacokinetic drug-drug interactions occur but go undetected, little evidence was found for occultly occurring drug interactions with newer antidepressants. The presence of commonly predicted drug interactions was documented. These data do not eliminate the need for caution when prescribing antidepressants with the potential for causing metabolic interactions, but do help allay the fear that such interactions are highly prevalent and routinely hazardous.
Women receiving any of the above mentioned hepatic enzyme-inducing medicinal or herbal products should be advised that the efficacy of Mercilon may be reduced. A barrier contraceptive method should be used in addition to Mercilon during administration of the hepatic enzyme-inducing medicinal product, and for 28 days after discontinuation of the hepatic enzyme-inducing medicinal product. If concomitant drug administration runs beyond the end of the tablets in the current COC pack, the next COC pack should be started right away without the usual tablet-free interval.