(W1030-08-53) Optimized HPLC Method for the Lacosamide and Its Impurities in the Lacosamide Injection

Purpose: Lacosamide (LCS) as an active pharmaceutical ingredient (API) can be analyzed by the USP (US Pharmacopeia) monograph recommended reversed-phase high-performance liquid chromatography (RP-HPLC) method (Fig 1). However, more impurities found in the evaluation of Lacosamide Injection. An optimized method must be established to determine the API and its impurities in the final product at the same time, in order to obtain better resolution between the target peaks.

Methods: First, the column length was increased. Agilent ZORBAX Eclipse XDB-C8, 5 µm, 250 mm × 4.6 mm column was selected. Then, gradient mobile phase combination instead of isocratic mobile phase were compared. Mobile phase A consisted of methanol/ acetonitrile/water/methanesulfonic acid (5:2:93:0.075, v/v/v/v), mobile phase B consisted of Methanol/acetonitrile/water (5:45:50:0.075, v/v/v/v) and mobile phase C consisted of methanol/acetonitrile/water/methanesulfonic acid (5:4:91:0.1, v/v/v/v), respectively. The analysis was carried out with the flow rate of 2.0 mL/min under wavelength of 215 nm with the column temperature at 35°C. The gradient was adjusted based on the results and specification.

Results: One unknown degradation compound interfered with the known impurity J (Fig 2) before method optimization. The impurity occurred in the stress study of acid and base hydrolysis. In the original method, the new occurred peak could not be discriminated completely. With the modified method, total 12 impurities and one active ingredient were separated with the resolution not less than 1.5 (1.7 to 31.0) for each adjacent target peaks (Fig. 3). The unknown degradation impurities can be monitored and identified clearly. This was applied in further study on the quality control for the finished product.

Conclusion: By altering the mobile phase composition, the mobile phase gradient and the column length, the developed method becomes more efficient. The method performance characteristics evaluated for lacosamide and its impurities in Lacosamide injection were specificity, linearity, accuracy, identity, precision, and robustness, and the newly developed method met all predefined performance acceptance criteria.

Fig 1. Chromatogram example of the USP monograph recommended RP-HPLC method

Fig 2. Chromatogram example of the interfered unknown peak with Imp J in stressed (acid hydrolysis) sample

Fig 3. Chromatogram of the resolution solution including all target impurities and the active ingredient in the final optimized method