Simultaneous Determination of Risperidone and Trihexhyphenidyl Hydrochloride from Bulk and Tablet Dosage Form by RP-HPLC

A simple, reverse phase high performance liquid chromatographic (HPLC) method was developed for the determination of Risperidone and Trihexyphenidyl hydrochloride in combined tablet dosage form. A octadecyl silane (ODS) C₁₈ Phenomenex Gemini (250mm X 4.6mm, i.d., 5μ) column, with mobile phase of 0.3% ortho phosphoric acid buffer, acetonitrile and methanol (50:30:20%v/v/v) adjusted to pH3 with triethylamine was used. The flow rate was 1mL/minute and the effluent was monitored at 220nm. The retention times for Risperidone and Trihexyphenidyl hydrochloride were 2.685±0.012 and 5.912±0.030 minutes respectively. The linearity range was found to be 4.8 μg/mL to 19.2 μg/mL for Risperidone and 3.2 μg/mL to 12.8 μg/mL for Trihexyphenidyl hydrochloride. The proposed method was validated as per ICH guidelines.