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Doxilamine orodispersible tablets were developed with considerable increase in drug release as compared to marketed formulations, seven formulations were developed and studied. The difference in drug release values was found to be 100.45 ± 1.89 and 56.47 ± 1.89, respectively. To prevent bitter taste and unacceptable odour of the drug, the drug was taste masked with weak cation exchange resins like Indion 234, Indion 204 and Indion 414. The drug was characterized according to different compendial methods, on the basis of identification by UV spectroscopy, pH, organoleptic properties and other tests. Among the three resins, one was selected for further studies i.e., Indion 234, because of high drug loading capacity. Drug-resin complex was prepared using batch method and effect of various processing parameters viz. drug-resin ratio, pH, temperature and drug concentration was studied to optimize the loading conditions. Maximum loading was obtained at drug-resin ratio 1:2, pH 5, temperature 50°C and drug concentration 4 mg/ml. A successful taste masking of resinate was confirmed by time intensity method and also by taking drug release in 0.01 N hydrochloric acid and in simulated salivary fluid. The values of pre-compression parameters evaluated, were within prescribed limits and indicated good free flowing properties. The data obtained of post-compression parameters such as weight variation, hardness, friability, wetting time, water absorption ratio, content uniformity, disintegration time and dissolution and was found superior over conventional formulation. The F5 batch with disintegration time 25.24 ± 0.75 and dissolution 100.46% ± 3.78 was selected as optimized formulation. This was compared with conventional marketed formulation and was found superior. Batch F5 was also subjected to stability studies for three months and was tested for its disintegration time, drug contents * Corresponding authors.

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Sildenafil citrate (SIL) is used in the treatment of erectile dysfunction and other chronic disorders. For the pharmacokinetic investigation of SIL we developed a simple and sensitive method for the estimation of SIL in rat plasma by reverse phase high-performance liquid chromatography (RP-HPLC). The drug samples were extracted by liquid-liquid extraction with 300 μl of acetonitrile and 5 ml of diethyl ether. Chromatographic separation was achieved on C18 column using methanol:water (85:15 v/v) as mobile phase at a flow rate of 1 ml/min and UV detection at 230 nm. The retention time of SIL was found to be 4.0 min having a separation time less than 5 min. The developed method was validated for accuracy, precision, linearity and recovery. Linearity studies were found to be acceptable over the range of 0.1-6 μg/ml. The method was successfully applied for the analysis of rat plasma sample for the application in pharmacokinetic study, drug interaction, bioavailability and bioequivalence.