Prediction of the impact of lubrication on tablet compactibility

The tableting of most pharmaceutical formulations requires the addition of lubricants to reduce ejection forces, prevent tooling damage and tablet defects. The internal addition of lubricants is known to reduce tablet tensile strength, especially of mainly plastically deforming materials. To date, available models show only limited quantitative predictive accuracy for the influence of lubricant concentration on the mechanical strength of tablets. This study aims to fill this gap and present a model based on the Ryshkewitch-Duckworth equation that can estimate the compactibility profiles of lubricated formulations. Binary mixtures of different diluents (microcrystalline cellulose and lactose) were prepared with common lubricants (magnesium stearate and sodium stearyl fumarate) and subsequently tableted. The resulting compactibility profiles were fitted using the Ryshkewitch-Duckworth equation and the derived fit parameters (k_b and σ₀) were correlated with the lubricant concentration. Subsequently, an empirical model was established which requires a minimum of experimental data and is able to predict the tensile strength of lubricated diluent tablets. Consequently, the developed empirical model is an interesting and valuable addition to the existing multi-component compacting models available and offers the opportunity to accelerate experimentation in the development of new tablet formulations.

Controlled drug release from pellets containing water-insoluble drugs dissolved in a self-emulsifying system

The aim of the study was to provide a controlled release system, which could be used for the oral administration of highly water-insoluble drugs. Pellets have been prepared by extrusion/spheronization containing two model drugs (methyl and propyl parabens) of low water solubility. One type of pellets contained the drugs mixed with lactose and microcrystalline cellulose (MCC) and the other types of pellets contained the model drugs dissolved in a self-emulsifying system (4.8%) consisting of equal parts of mono-diglycerides and polysorbate 80 and MCC. Pellets of all types in the same size fraction (1.4-2.0 mm) were coated to different levels of weight gain, with ethylcellulose, talc and glycerol. A sample of pellets containing methyl parabens in the self-emulsifying system was pre-coated with a film of hydroxypropylmethyl cellulose from an aqueous solution and then coated as above. Dissolution experiments established that the presence of the self-emulsifying system enhanced the drug release of both model drugs and that the film coating considerably reduced the drug release from pellets made with just water, lactose and MCC. The coating reduced the drug release from the pellets containing the self-emulsifying system to a lesser extent but in relation to the quantity of coat applied to the pellets. The application of a sub-coating of hydroxypropylmethyl cellulose was able to reduce the release rate of methyl parabens self-emulsifying system ethyl cellulose coated pellets. Thus, the formulation approach offers the possibility of formulating and controlling the in vitro release of water-insoluble drugs from solid oral dosage forms.