Commentary: Liquid-filled Formulations

Nowadays, the pharmaceutical industry is facing an increasing numbers of low solubility drug candidates and this issue often hinders those compounds from achieving sufficient oral bioavailability. In order to alleviate this challenge, many enabling formulation technologies have been developed. Of these, liquid- filled capsules have emerged as one of the key technologies for oral drug delivery of low solubility compounds. A liquid-filled capsule (LFC) is a liquid formulation encapsulated in a soft or hard capsule. In general, lipids and/or co-solvents are the most commonly solubilizing excipients in LFCs. Although developing and manufacturing LFCs is non-trivial and challenging, they possess distinct advantages over traditional solid dosage forms. For example, improving oral exposure (or faster on-set) of poorly soluble drugs, allowing the use of API with challenging solid state properties (i.e. hard to crystallize), overcoming content uniformity issues with low dose drugs, reducing exposure to dust from high potency compounds, and other specific purposes such as prevention of drug abuse. Therefore, despite the challenges associated with LFCs, they remain an important option for formulators. Three major types of liquid-filled formulations currently being employed in the industry will be be briefly discussed in this article.