Melt extrusion: from process to drug delivery technology

Interest in hot-melt extrusion techniques for pharmaceutical applications is growing rapidly with well over 100 papers published in the pharmaceutical scientific literature in the last 12 years. Hot-melt extrusion (HME) has been a widely applied technique in the plastics industry and has been demonstrated recently to be a viable method to prepare several types of dosage forms and drug delivery systems. Hot-melt extruded dosage forms are complex mixtures of active medicaments, functional excipients, and processing aids. HME also offers several advantages over traditional pharmaceutical processing techniques including the absence of solvents, few processing steps, continuous operation, and the possibility of the formation of solid dispersions and improved bioavailability. This article, Part I, reviews the pharmaceutical applications of hot-melt extrusion, including equipment, principles of operation, and process technology. The raw materials processed using this technique are also detailed and the physicochemical properties of the resultant dosage forms are described. Part II of this review will focus on various applications of HME in drug delivery such as granules, pellets, immediate and modified release tablets, transmucosal and transdermal systems, and implants.

Pharmaceutical Applications of Hot-Melt Extrusion: Part I

Hot-melt extrusion (HME) is a promising technology for the production of new chemical entities in the developmental pipeline and for improving products already on the market. In drug discovery and development, industry estimates that more than 50% of active pharmaceutical ingredients currently used belong to the biopharmaceutical classification system II (BCS class II), which are characterized as poorly water-soluble compounds and result in formulations with low bioavailability. Therefore, there is a critical need for the pharmaceutical industry to develop formulations that will enhance the solubility and ultimately the bioavailability of these compounds. HME technology also offers an opportunity to earn intellectual property, which is evident from an increasing number of patents and publications that have included it as a novel pharmaceutical formulation technology over the past decades. This review had a threefold objective. First, it sought to provide an overview of HME principles and present detailed engineered extrusion equipment designs. Second, it included a number of published reports on the application of HME techniques that covered the fields of solid dispersions, microencapsulation, taste masking, targeted drug delivery systems, sustained release, films, nanotechnology, floating drug delivery systems, implants, and continuous manufacturing using the wet granulation process. Lastly, this review discussed the importance of using the quality by design approach in drug development, evaluated the process analytical technology used in pharmaceutical HME monitoring and control, discussed techniques used in HME, and emphasized the potential for monitoring and controlling hot-melt technology.

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Hot-Melt Extrusion: from Theory to Application in Pharmaceutical Formulation

Introduction: Eudragit is the brand name for a diverse range of polymethacrylate-based copolymers. It includes anionic, cationic, and neutral copolymers based on methacrylic acid and methacrylic/acrylic esters or their derivatives. Areas covered: In this review, the physicochemical characteristics and applications of different grades of Eudragit in colon-specific/enteric-coated/sustained release drug delivery and taste masking have been addressed. Expert opinion: Eudragits are amorphous polymers having glass transition temperatures between 9 to > 150oC. Eudragits are non-biodegradable, nonabsorbable, and nontoxic. Anionic Eudragit L dissolves at pH > 6 and is used for enteric coating, while Eudragit S, soluble at pH > 7 is used for colon targeting. Studies in human volunteers have confirmed that pH drops from 7.0 at terminal ileum to 6.0 at ascending colon, and Eudragit S based systems sometimes fail to release the drug. To overcome the shortcoming, combination of Eudragit S and Eudragit L which ensures d...

Eudragit®: a technology evaluation

Use of surfactants as plasticizers in preparing solid dispersions of poorly soluble API: selection of polymer-surfactant combinations using solubility parameters and testing the processability.

Hot-melt screw extrusion was presented as an alternative method for producing polymer-based sustained release pellets. Special care was paid to the case of highly dosed freely soluble drugs which often pose technological problems with the usual manufacturing processes. In a preformulation study, polymers, plasticizers and drugs were selected according to various criteria including thermal stability. During these preliminary tests, the optimum extrusion conditions were defined. Four polymers were considered for extrusion trials, namely ethylcellulose, cellulose acetate butyrate, poly(ethylene-co-vinyl acetate) and a polymethacrylate derivative (Eudragit® RSPM). Pellets were produced with diltiazem hydrochloride as model drug. The surface appearance of various formulations was examined and the porosity assessed by means of mercury porosimetry. A distinct structure was found for the EVAC-based pellets. The overall porosity was less than 10%. Lastly, in vitro release of the drug showed a biphasic prof...

Evaluation of hot-melt extrusion as a new technique for the production of polymer-based pellets for sustained release capsules containing high loadings of freely soluble drugs

Nicolas Follonier

Papers

Evaluation of hot-melt extrusion as a new technique for the production of polymer-based pellets for sustained release capsules containing high loadings of freely soluble drugs

Various ways of modulating the release of diltiazem hydrochloride from hot-melt extruded sustained release pellets prepared using polymeric materials