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Abstract. The influence of experimental temperature on the permeability of model diffusants across porcine buccal mucosa was investigated in vitro. The permeability increased significantly as the experimental temperature was increased in increments of approximately 7°C. It was observed that the apparent permeability and temperature were related by an exponential relationship that conformed to the Arrhenius equation. Diffusants with higher lipophilicities-buspirone and bupivacaine-had lower activation energies for diffusion when compared to hydrophilic diffusants-antipyrine and caffeine. The activation energy for diffusion of the model diffusants decreased linearly with increasing distribution coefficients across porcine buccal mucosa. The results suggested that the buccal mucosa acts as a stronger barrier to the diffusion of hydrophilic diffusants than the lipophilic ones. The log-linear relationship between permeability and temperature indicates that temperature should be carefully controlled in diffusion experiments. These results also point to the possibility of developing heat-generating buccal delivery devices, especially for hydrophobic diffusants.

Felodipine which is used in the present study is a dihydropyridine derivative, that is chemically described as ethyl methyl-4-(2, 3-dichlorophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate, widely accepted for its excellent antihypertensive and anti-anginal properties since it is calcium antagonist compound (calcium channel blocker). Felodipine is practically insoluble in water and its dissolution rate is limited by its physicochemical properties. In the present study fast disintegrating tablets of felodipine were prepared by adopting vacuum drying technique to study the effect of different subliming agents with various concentrations on disintegrating time. The powder blend was examined for the pre-compressional parameters. The prepared formulations were evaluated for post-compressional analysis for the parameters like hardness, friability, thickness, wetting time, water absorption ratio, weight variation, in-vitro disintegration time, in- vitro dispersion time, in-vitro dissolution study. Drug compatibility with excipients was checked by FTIR studies. The results obtained showed that quantity of ammonium bicarbonate, urea and menthol significantly affect the response variables (P> 0.05). No chemical interaction between drug and excipients was confirmed by FTIR studies. Stability studies carried out as per ICH guidelines for three months and results revealed that upon storage disintegration time of tablets decreased significantly (P> 0.05). The results concluded that fast disintegrating tablets of felodipine showing enhanced dissolution rate with increasing the concentrations of subliming agents. Among all the formulations A3 and M3 shows the improved dissolution rate which lead to improved bioavailability and effective therapy by using vacuum drying technique.

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