HPLC Chromatographic Methods for Simultaneous Determination of Pholcodine and Ephedrine HCI with Other Active Ingredients in Antitussive-Antihistamine Oral Liquid Formulations

A description of simple, isocratic and precise reversed phase HPLC methods is given for simultaneous quantification of pholcodine and ephedrine hydrochloride together with either carbinoxamine maleate or terfenadine in antitussive-antihistaminic oral pharmaceutical formulations. Separations were carried out on X-Terra and symmetry shield C18 column $(250\;{\times}\;4.6\;mm,\;5\;{\mu}m)$. The used isocratic elution systems were either $0.02\;M\;KH_2PO_4-acetonitrile$ in the ratio of 75 : 25 and pH adjusted to 7.70 with orthophosphoric acid or sodium hydroxide, for syrup (method A), or 0.02 octanesulphonic acid sodium salt solution-acetonitrile-acetic acid in the ratio of 75 : 25 : 0.5 for suspension (method B). The elution of both mixtures was achieved with a flow rate of 1 ml/min. Detection was carried out by UV absorbance at wavelengths of 220 and 250 nm for syrup and suspension, respectively. The quantification of the components in synthetic mixtures and actual syrup and suspension were calculated using the internal standard technique with metoclopramide HCl and codeine phosphate as internal standards (IS), respectively. The methods, for both mixtures, were validated and met all the requirements for the quality control analysis recommended by FDA and ICH.