James Kowalski

Application of Melt Extrusion in the Development of a Physically and Chemically Stable High-Energy Amorphous Solid Dispersion of a Poorly Water-Soluble Drug

Formulation of active pharmaceutical ingredients (API) in high-energy amorphous forms is a common strategy to enhance solubility, dissolution rate and, consequently, oral bioavailability of poorly water-soluble drugs. Amorphous APIs are, however, susceptible to recrystallization and, therefore, there is a need to physically stabilize them as solid dispersions in polymeric carriers. Hot melt extrusion has in recent years gained wide acceptance as a method of choice for the preparation of solid dispersions. There is a potential that the API, the polymer or both may degrade if excessively high temperature is needed in the melt extrusion process, especially when the melting point of the API is high. This report details a novel method where the API was first converted to an amorphous form by solvent evaporation and then melt-extruded with a suitable polymer at a drug load of at least 20% w/w. By this means, melt extrusion could be performed much below the melting temperature of the drug substance. Since the glass transition temperature of the amorphous drug was lower than that of the polymer used, the drug substance itself served as the plasticizer for the polymer. The addition of surfactants in the matrix enhanced dispersion and subsequent dissolution of the drug in aqueous media. The amorphous melt extrusion formulations showed higher bioavailability than formulations containing the crystalline API. There was no conversion of amorphous solid to its crystalline form during accelerated stability testing of dosage forms.

Application of melt granulation technology to enhance tabletting properties of poorly compactible high-dose drugs

Using metformin HCl as the model drug and hydroxypropylcellulose (HPC) as the polymeric excipient, a melt granulation (MG) process that employs a twin-screw extruder has been developed to enhance compactibility of poorly compactible high-dose drug substances. A high (90%) drug-load tablet formulation, containing 1025 mg of active pharmaceutical ingredients and 109 mg of excipients, was produced. Drug-polymer-powder mixtures were melt granulated at a temperature above glass transition of HPC (130°C) but below melting point of metformin HCl (224°C). MG was compared with modified wet granulation (WG) and solvent granulation (SG) processes. Under identical compression force, the hardness of tablets produced was MG>SG>WG and the friability was MG<SG<WG. The hardness of WG tablets was highly sensitive to moisture content both during compression and subsequent storage, and, although not to the same extent, the hardness of SG tablets was also affected by loss-on-drying levels. MG provided a robust manufacturing process with highest compactibility and lowest friability that were not sensitive to changes in atmospheric moisture level. The process can decrease tablet sizes of high-dose drugs and combination products by decreasing the need for relatively large amounts of excipients generally used to overcome physicochemical limitations of drug substances.

Application of melt granulation technology to enhance stability of a moisture sensitive immediate-release drug product

The preparation of tablets by the melt granulation process was investigated to enhance chemical stability of a highly water-soluble drug substance, dipeptidylpeptidase IV (DPP-IV) inhibitor (Compound I), that is susceptible to degradation in presence of moisture. Melt granulation with a lipophilic binder (hydrogenated castor oil; Cutina HR) improved the stability of the drug, while still maintaining immediate-release characteristics of the drug product. The drug to binder ratio was shown to impact the degradation behavior of the drug product. With higher binder levels, the sensitivity of the drug to degradation under humidity conditions decreased. It is postulated that the lipophilic binder coated drug particles at the surface protecting them from the influence of moisture. The granules had good flow properties and good compressibility and tablets prepared from them exhibited low weight variation and low friability.