Impact of plant extracts on drug transport across intestinal mucosa

Plant materials in the form of fruit, vegetables or herbal medicines are often taken in conjunction with allopathic medicines. Pharmacodynamic and/or pharmacokinetic interactions may occur between phytoconstituents and the co-administered drug [1]. Pharmacokinetic interactions include interferences with drug delivery and distribution by means of altered absorption, metabolism, distribution and/or elimination [2]. This work reports on the effects of extracts from traditional medicinal plants (Hypoxis hemerocallidea and Sutherlandia frutescens), fruit (Sclerocarya birrea, Psidium guajava, Dovyalis caffra, Prunus persica, Fragaria ananassa, Prunus domestica), herbs (Aspalathus linearis) and vegetables (Daucus carota, Beta vulgaris) on drug transport. The transport was measured in both directions (apical to basolateral and basolateral to apical) across Caco-2 cell monolayers and pig intestinal tissues to identify effects on the active efflux of the drug in the basolateral to apical direction. The results showed that some of the investigated plant extracts decreased drug efflux probably by inhibition of P-glycoprotein resulting in increased drug absorption, while others increased the efflux with a subsequent decrease in absorption. Although in vitro pharmacokinetic interactions are not always clinically significant in the in vivo situation [3], it may indicate potential changes in the bioavailability of co-administered drugs.

References: 1. Harris R.Z. et al. (2003) Clin. Pharmacokinet. 42:1071–1088.

2. Manzi S.F. et al. (2005) Clin. Pediatr. Emerg. Med. 6:93–102.

3. Farkas et al. (2008) Expert Opin. Drug Metab. Toxicol. 4:381–39.