The formulation of a drug into small discrete units coated with a film has gained much attention, particularly as such formulations exhibit great flexibility in dosage and modification of release properties. This approach allows different dosage forms to be developed and dose size is adaptable to suit fixed combinations.
To date this type of tablet has generally been made using a film coating sprayed from a solution of ethyl cellulose and hydroxypropyl methyl cellulose in an organic solvent.
But for environmental reasons, it will be necessary in the near future to use water based film forming systems for this and other drugs to be formulated as pellet systems, according to AstraZeneca. And volatile solvent use can also present processing difficulties and impact on operator safety.
Furthermore, while polymer-based coatings have been developed that can be processed in an aqueous environment, such as FMC's Aquacoat, Rohm Pharma's Eudragit and BASF's Kollicoat, they require anti-sticking additives (e.g. glyceryl monostearate) or plasticisers (e.g. triethyl citrate) to get the best results.
AstraZeneca's new US patent (No 6,827,947), describes a film coating that is water-based and is non-sticky, has high mechanical strength and reproducibility, during processing and requires minimal addition of extra additives to the dispersion before the film forming process.
The invention provides a film coating composition suitable for use in coating pharmaceutical formulations to provide modified release comprising a dispersion and comprises an acrylic polymer, a vinyl acetate polymer, a water-containing liquid, and a stabiliser.