Fruit juice, organic anion transporting polypeptides, and drug interactions in psychiatry

Organic anion transporting polypeptides (OATPs) are a group of membrane transport proteins that facilitate the influx of endogenous and exogenous substances across biological membranes. OATPs are found in enterocytes and hepatocytes and in brain, kidney, and other tissues. In enterocytes, OATPs facilitate the gastrointestinal absorption of certain orally administered drugs. Fruit juices such as grapefruit juice, orange juice, and apple juice contain substances that are OATP inhibitors. These fruit juices diminish the gastrointestinal absorption of certain antiallergen, antibiotic, antihypertensive, and β-blocker drugs. While there is no evidence, so far, that OATP inhibition affects the absorption of psychotropic medications, there is no room for complacency because the field is still nascent and because the necessary studies have not been conducted. Patients should therefore err on the side of caution, taking their medications at least 4 hours distant from fruit juice intake. Doing so is especially desirable with grapefruit juice, orange juice, and apple juice; with commercial fruit juices in which OATP-inhibiting substances are likely to be present in higher concentrations; with calcium-fortified fruit juices; and with medications such as atenolol and fexofenadine, the absorption of which is substantially diminished by concurrent fruit juice intake.