Delivery of glipizide from asymmetric membrane capsules using encapsulated excipients

The aim of this study was to demonstrate that the asymmetric membrane capsule can be used to deliver a poorly water soluble drug with a pH sensitive solubility such as glipizide. In order to obtain the desired delivery duration, the drug was solubilized with the use of a pH-controlling excipient. In osmotic systems, the release rate of an excipient relative to the release rate of the drug is an important factor that determines the duration of drug release. Thus, highly water-soluble excipients are released much faster than the drug, which can limit their usefulness. In the case of the asymmetric membrane capsule, it was shown that this limitation could be overcome by encapsulating the pi-I-controlling excipient in a membrane and including the coated excipient in the asymmetric membrane capsule core to prolong its availability within the core. Thus, prolonged release of glipizide could be obtained with the asymmetric membrane capsule. (C) 1999 Elsevier Science B.V. All rights reserved.