Purpose: Extracts made from berries, herbs, and various plant materials, which might possess a range of activities, are used as health promoting products. Because little is known about their effects on the absorption of co-administered drugs, the effects of some food supplements, Finnish berries, and herbs were studied on the permeability of some commonly used drugs.
Methods: The permeabilities of verapamil, metoprolol, ketoprofen, paracetamol, and furosemide were studied across Caco-2 cell monolayers with contemporaneously administered extracts from flax seed, purple loosestrife, and Scots pine bark; bilberries, cowberries, and raspberries; oregano, rosemary, and sage. Toxicological tests were conducted to determine cellular damage.
Results: The effects of extracts on drug permeabilities were generally minor. Flax seed decreased the permeability of all drugs except verapamil. Purple loosestrife and pine decreased verapamil and metoprolol permeability. Changes caused by berries were mainly pH-related. Rosemary and oregano enhanced furosemide permeability.
Conclusions: Ingestion of extracts of herbs and berries studied are not expected to markedly change the permeabilities of highly permeable drugs. Harmful effects at sites of or during absorption are unlikely. However, if high doses of extracts are administered with low permeable drugs in vitro, effects on drug permeabilities could not be excluded. Use of such extracts should therefore be evaluated during continuous medication.