Active Agents Melt Extrusion Improves Bioavailability of Low-solubility Active Agents
“The right place at the right time” — so runs the slogan of the innovative drug delivery systems and active agent formulations developed by Evonik. It has also just started applying to active agents of low solubility as well: in melt extrusion, Evonik has found a technology that significantly enhances the bioavailability of these agents.
Functional polymers can act in response to pH levels or be controlled by time when releasing an active agent at the desired place in the gastrointestinal tract. Not only do they determine when and where the active agent is released, they can do much more besides: when used as a coating they mask the smell and taste of a tablet — a major advantage, especially when treating children — and they make sure that the active agent arrives intact at its intended destination. The polymers shield the active agent from moisture, for example, or from the gastric acid, and funnel it safely to the resorption site in the small or large intestine.
Scientists in the research centers of the Evonik Pharma Polymers division in Germany, India, China, Japan and the USA are conducting research into new polymers and developing formulations with Eudragit polymers to customer specifications.
Bioavailability Determines the Efficiency of the Active Agents
The bioavailability of an active agent indicates the extent to which it enters the circulation after administration of a pharmaceutical. It is a key ratio and therapeutic variable and provides such information as the measure of efficiency of a drug. The more easily soluble an active agent is and the better it is taken up by the cells at the absorption location (gastrointestinal tract, mucous membranes, skin, etc.) and transferred to the bloodstream, i.e. resorbed, the better its bioavailability in most cases.
The active agents can be divided into four classes under the Biopharmaceutics Classification System (BCS) depending on their solubility and cell penetrability (permeability). 40 percent of the medicines currently supplied have a solubility problem (L.Benet, C.-Y. Wu et al 2006, Bulletin technique Gattefosse 99; p. 9-16). This percentage is as high as 95 percent with new developments. Indeed, due to the computer screening of active agents practiced in the industry, development is concentrated on lipophilic agents as these interact particularly well with the respective site of their effective action. Yet the more lipophilic a substance is, the less effective it is at dissolving in the watery environment of the gastrointestinal tract.
Biopharmaceuticals currently account for 16 percent of medicines sold and 15 to 25 percent of the new medicinal products brought to market in Germany every year. The most common form of administration is parenteral, usually by injections into the vein. If administered perorally, i.e. by mouth, they would normally be already digested in the gastrointestinal tract, inactivated and also poorly resorbed. New modular systems developed by Evonik are opening the door to the development of formulations which can be applied perorally for small and medium-sized biopharmaceuticals.