Shedding light on interaction of so called inactive ingredients (excipients) with permeability-glycoprotein

Permeability glycoprotein (P-gp) is a 170 kDa membrane transporter from the category of efflux pumps, which is situated at the apical site of epithelial membrane. P-gp is known to efflux diverse classes of chemical compounds including anticancer agents, antibiotics, steroidal compounds and many more.

Numerous strategies have been used to inhibit the efflux of such compounds via efflux transporters including co-administration with P-gp inhibitors, chemical modifications and others, with limited success. Excipients (so called inactive ingredients) are intentionally added in drug formulations to alter characteristics of drug. Nowadays, there is increasing interest in investigating these traditionally used excipients for their efflux pump inhibitory potential, as they have been reported to cause subtle changes, that can affect transporter proteins (efflux pumps) on cell membrane.

Many reviews have explained the role of specific P-gp inhibitors for improved drug delivery, however there is not much data when it comes to exploring an excipient for its inherent function and P-gp inhibitory potential. This review will shed light on current status of excipients, which can be used to modulate membrane transporter inhibition potential and discuss the mechanism involved in it. Certain preparations, formulated using such excipients which enhances drug absorption and minimize related toxicity, will be also discussed. Continue on drug delivery improvement with excipients