Bioadhesive Polymer Buccal Patches for Buprenorphine Controlled Delivery: Formulation, In-vitro Adhesion and Release Properties

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Abstract
A new bioadhesive polymer patch formulation for buprenorphine controlled delivery and consisting of polyisobutylene, polyisoprene, and Carbopol® 934P was prepared using a two-roll milling method. Carbopol® 934P was the bioadhesive of choice for the current formulation because it demonstrated a higher average peeling strength than hydroxypropyl methylcellulose, chitosan, or acacia as measured during in vitro testing. Other in vitro analyses showed that the milling process did not alter the viscosity or the thermodynamic and rheologic properties of polyisobutylene and polyisoprene. Nearly 75% of the buprenorphine was released from the patches following a 24 hour incubation in phosphate buffer (pH = 7). Data obtained from dissolution studies suggested that the major mechanism of buprenorphine release is patch swelling. It was also shown that patch adhesion increased with increasing thickness and up to three months of aging had little effect on adhesive properties. In addition, this formulation maintained the majority of its adhesive strength for at least 24 hours with a linear decline in average peeling load thereafter. In conclusion, buccal patches consisting of a homogeneous mixture of polyisobutylene, polyisoprene, and Carbopol® 934P formed by a two-roll milling process appear to possess physical properties that are well suited for the transmucosal controlled delivery of buprenorphine.