International journal of pharmaceutics
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Comparative Study Clinical Trial
In vitro percutaneous penetration of topically applied capsaicin in relation to in vivo sensation responses.
Capsaicin, the primary pungent element in several spices, elicits a variety of physiological effects which are due to neurogenic responses. The aim of the study was to explore the in vivo sensation responses of capsaicin and to compare the results with the in vitro percutaneous absorption of the substance. The overall objectives were to determining an in vitro-in vivo correlation for capsaicin. ⋯ Percutaneous steady-state penetrations of capsaicin with a receptor fluid consisting either of 4% bovine serum albumin in phosphate buffered saline or 50% ethanol in water were 28.2+/-2.7 and 29.6+/-2.9 microg/cm(2) per h, respectively. The corresponding cumulative penetrated amounts of capsaicin after 30 min were 14. 7+/-1.7 and 19.2+/-2.1 microg/cm(2), respectively. The present investigation indicates that there is a good correlation between in vivo physiological responses and in vitro percutaneous penetration of topically applied capsaicin.
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The ex vivo buccal permeability of a [D-Ala(2), D-Leu(5)]enkephalin (DADLE) and glyceryl monooleate (GMO) was examined from the cubic and lamellar liquid crystalline phases of GMO and aqueous phosphate-buffered saline (pH 7.4, PBS) solution across excised porcine buccal mucosa mounted in a Franz cell. GMO was released in vitro from the liquid crystalline phases indicating the erosion of the liquid crystal matrices. ⋯ The flux of DADLE (1.21+/-0.32 and 1. 15+/-0.11%/cm(2) per h for the cubic and lamellar phases, respectively) from the liquid crystalline phases was significantly enhanced by the GMO compared with PBS solution (0.43+/-0.08%/cm(2) per h) during the initial permeation phase (t<3 h). Our results suggest that the cubic and lamellar liquid crystalline phases can be considered as promising buccal drug carriers for peptide drugs as well as acting as permeation enhancers.