Finally, the pharmacodynamic effects of propranolol powder formulation with different buffering were carried out in two healthy male subjects. The maximal reduction in heart rate was found at the saliva pH of 7.6, which corresponded to the pHmax of propranolol. A buffered propranolol sublingual tablet was then prepared to achieve the saliva pH around 7.6. The preliminary investigation confirmed that the sublingually administrated buffered propranolol tablet produced a faster and more pronounced heart rate reduction than the non-buffered commercial propranolol tablet. / Firstly, the use of the HO-1-u-1 cell culture for screening sublingual drug delivery was validated. The cells were seeded on cell culture inserts. The integrity of cell layers, inter-passage variation and directionality were assessed by measuring the resistance and the permeability of standard markers, beta-blockers and calcium channel blockers. The effect of pH, osmolarity and a permeation enhancer (GDC) were also studied. The results showed that HO-1-u-1 cells grown on inserts formed stratified and epithelial-like structure that preserved the typical histological feathers of the normal human sublingual epithelium. The maximal integrity was reached in 23 days. The Papp of beta-blockers and calcium channel blockers ranged from 2.89+/-0.17 x 10 -6 cm/s to 6.37+/-0.37 x 10-6 cm/s. The permeability of selected beta-blockers under different pH, osmolarity and GDC revealed that enhancing effects were significant for hydrophilic compounds but less for lipophilic compounds. / Secondly, fresh porcine sublingual mucosa was prepared and compared to the cell line model. Good correlations were obtained for both the Papp of beta-blockers and the enhancement ratios of pH and GDC between the two models. / The aims of the present study are (1) to develop and validate a human sublingual epithelial cell line model and (2) to demonstrate the application in sublingual development of cardiovascular drugs. / Thirdly, the steady-state flux (Jss) at various pH levels were measured. Results show that saturated propranolol solution at pH 7.0--7.6 resulted in a much higher Jss than the solution at other pHs. These data led to the development of theoretical equations for predicting the optimum pH (pHmax) for ionizable compounds. The calculation fitted well with the experimental data. / Wang Yanfeng. / Advisers: Moses S. S. Chow; Zhong Joan Zuo. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 184-). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.