In Vitro Release and Permeation of Oxytocin from a Mucoadhesive Buccal Patch

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Abstract
A biocompatible, mucoadhesive patch was evaluated for potential use in the delivery of peptides. The model peptide oxytocin was incorporated into the polymeric patch matrix and the diffusion of oxytocin across excised rabbit buccal epithelium was studied following patch application. Penetration of oxytocin across excised mucosa from an applied patch did not exhibit a characteristic lag time for diffusion, with the steady-state flux of oxytocin being 0.062 ± 0.019 μg/cm2/hr. However, when finite-dose diffusion studies were conducted to quantitate transport of oxytocin across rabbit buccal mucosa, the mean apparent permeability coefficient (P), diffusion coefficient (D), partition coefficient (K), and lag time (tlag) were (1.94 ± 0.74) × 10−7 cm/sec, (9.20 ± 1.65) × 10−8 cm2/ sec, 0.13 ± 0.05 and 1.86 ± 0.31 hr, respectively. The release of oxytocin from the mucoadhesive buccal patches in vitro proceeded very rapidly during the first 2 hr, with 72% of the amount initially incorporated into the patches released at 24 hr. The disappearance rate of intact, parent oxytocin when an oxytocin solution was placed in direct contact with the serosal and mucosal sides of freshly excised rabbit buccal mucosa was 0.74 ± 0.34 μg/cm2/hr and 3.38 ± 1.07 μg/cm2/hr, respectively. Thus, the buccal patch evaluated in these studies appears to be suitable for transmucosal delivery of peptides.