Abstract
The use of herbal medicines alongside conventional drugs for the therapeutic management of diseases is common practice particularly in chronic conditions. A recent field study carried out in Nigeria showed that more than 50% of diabetic patients co-administer herbal preparations with their prescription medicines, thereby raising the risks of herb-drug interactions.
Thirty medicinal plants traditionally used for the management of diabetes in different areas of Nigeria were collected during the field work for
in-vitro
pharmacokinetic investigations to identify potential herb-drug interactions. The ability of these plants to modulate the effect of the intestinal efflux transporter P-glycoprotein (P-gp) was determined in Caco-2 cells using the fluorescent P-gp substrate, rhodamine-123.
At concentrations ≤100µg/ml, aqueous extracts of
Annona senegalensis, Bridelia ferruginea
and
Khaya senegalensis
significantly inhibited the efflux of accumulated rhodamine-123 from the cells. The inhibition was either comparable or much higher than that produced by 20µM verapamil, a known P-gp inhibitor. Aqueous extracts of
Syzygium guineense
and
Isoberlinia doka
on the other hand enhanced the efflux of rhodamine-123 from the cells.
These results suggest the possibility of interactions when these extracts are co-administered with prescription medicines which are also P-gp substrates such as glibenclamide.