A Stability Indicating Reversed-Phase HPLC Method for Determination of Pyrantel and Its Related Substances in Commercial Bulk Batches of Pyrantel Pamoate

Pyrantel is used as an active pharmaceutical ingredient (API) in both human and veterinary drug products. It is widely available as pyrantel pamoate (PP) and is also referred to as pyrantel embonate. It acts as a depolarizing neuromuscular blocking agent, causing paralysis in parasitic worms (helminths). The objective of this work was to develop an efficient, selective, and robust reversed phase high-performance liquid chromatography (RP-HPLC) method to determine PP and its related impurities in bulk API batches. The new method utilizes a Waters Xselect®HSS T3 column (100 mm × 4.6 mm i.d., 2.5 μm particle size) at 30 °C, with 0.1% TFA in H2O as mobile phase A and 100% methanol as mobile phase B. Analytes were separated by gradient elution at a flow rate of 1.0 mL/min and were detected by UV at 280 nm, except for impurity D (at 215 nm). The total run time of the method is 18 minutes. Unlike the PP methods prescribed in USP and Ph. Eur., the new HPLC method described in this paper adequately separates all peaks of interest and have demonstrated excellent robustness and reproducibility across various varied conditions. The results of forced degradation studies confirmed its stability-indicating capability. The validation results demonstrated that the new method is accurate, robust, specific, and stability-indicating. One of the key strengths and highlight of the new method is its capability in resolving the co-eluting peaks under the conditions of the USP/Ph. Eur. Methods.