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Effect of Hydroxylpropylated beta Cyclodextrin and pH on Solubility of Telmisartan

B. D. Shewale, P. O. Patil, P. K. Deshmukh and R. A. Fursule

The present study was undertaken to examine the effect of pH and concentration of hydroxypropylated-0-cyclodextrin (HP-0-CD) on the solubility of telmisartan as it shows the pH dependent solubility. The equilibrium solubility of telmisartan in a series of solutions of varying pH (from 1.2 to 11) was determined and compared with the equilibrium solubility of telmisartan in the presence of 20% HP-0-CD at same pH values. It was observed that solubility of protonated form is more than the neutral molecule. HP-0-CD resulted in increased solubility at all the pH. But inclusion in the cavity of HP-0-CD might depend upon charge state of the molecule. So it can be concluded that solubility of telmisartan can be increased either by the addition of HP-0-CD or by adding pH lowering agents. If both these methods are to be used together, pH should be selected carefully.