CYP450 isoenzyme-associated food-drug interactions are a neglected issue in medicines information.

Background
Interactions are occurring in the course of the release, absorption, distribution, metabolism, and excretion of active ingredients, or at the target receptors. Two concomitantly used substances interact with a probability of 13%, 4 with 38%, and 7 with 82%. Therefore, the elevated number of components in food may result in an alarmingly high frequency of food-drug interactions and, consequently, in pharmacotherapy failure.

Purpose
To assess whether adequate information on food-drug interactions is made available from medicines manufacturers.

Material and methods
All online monographs according to the “Questionnaire for the information of hospital pharmacists about proprietary medicines” were retrieved from http://www.gsasa.ch and screened for information on interactions involving food.

Results
From a total of 157 monographs, 90 (57%) declared that food-drug interactions were “not applicable”, “unknown”, or stated that “no data” were available. 23 (15%) explicitly mentioned that their medicine ”…is not affected by food”. 6 monographs (4%) reported an interaction during release and 1 (<1%) during excretion. 37 (23%) disclosed a bioavailability and metabolism interaction as a result of food intake: While 19 were restricted to concise information on delayed absorption from the GI tract which however would not decrease the amount of medicine absorbed, only 18 hinted at CYP450 isoenzyme-associated interactions, but generally limited their comments to grapefruit juice or St. John’s Wort.

Conclusion
Food-drug interactions have consequences which go beyond absorption from the GI tract. Although many food ingredients such as caffeine, flavonoids, liquorice, spices, and vitamins are known to be inducers or inhibitors of some of the 57 known human CYP450 isoenzymes [cf. Flockhart Interaction Table, Drugbank, SuperCYP], they are not taken into account in the medicines’ information made available by manufacturers. Thus, risks arising from isoenzyme-associated food-drug interactions are a neglected aspect of drug information.