Oral sustained release dosage forms comparison between matrices and reservoir devices

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Abstract
For the formulation of a monolithic controlled release form for oral use, containing 80 mg of a highly soluble drug, different systems have been compared. At first, matrices where prepared containing 37.3 percent of a water soluble polymer: HPMC (Methocel or Metolose) and HEC (Natrosol). With such swelling agents, it is quite difficult to reach a zero order release. But industrial scale-up is easy, because the process uses only classical machines. Variations intra and between batches have been found very small and stability is good. An other possibility is a lipophilic matrix. Hard gelatin capsules were filled with a drug dispersion in Gélucire of different grades. The fabrication process is quite easy but at this time, few informations about stability are available. A third convenient way is a reservoir device, a tablet coated with an insoluble polymer film (Aquacoat ECD 30). A zero order release was obtained until 80 percent of drug released after 12 hours. But the coating is a very critical phase of the process: disturbances affect the drug dissolution rate. The film may also be altered by the patient, who can break or crunch the tablet. In this case, all the drug is dissolved quasi instantaneously. For all these reasons, the hydrophilic matrix was preferred, especially if a zero order is obtained.

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