Stability-indicating methods for the determination of racecadotril in the presence of its degradation products

Three stability-indicating methods were developed for the determination of racecadotril (RCT) in the presence of its alkaline degradation products. The first was an HPLC method in which efficient chromatographic separation was achieved on a C18 analytical column and a mobile phase of acetonitrile-methanol-water-acetic acid (52:28:20:0.1, v/v/v/v). Linearity was obtained in the range of 4-40 microg/mL with mean accuracy of 99.5 +/- 0.88%. The second method was a densitometric evaluation of thin-layer chromatograms of the drug using a mobile phase of isopropanol-ammonia (33%)-n-hexane (9:0.5:20, v/v/v). The chromatograms were scanned at 232 nm, a wavelength at which RCT can be readily separated from its degradation products and determined in the range of 2-20 microg per spot with mean accuracy of 99.5 +/- 0.56%. The third method is based on the use of first-derivative spectrophotometry (D1) at 240 nm, and the drug was determined in the range of 5-40 microg/mL with mean accuracy of 99.2 +/- 1.02%. The three methods provided satisfactory recovery of the intact drug (100.8 +/- 0.82, 100.4 +/- 0.55, and 99.9 +/- 0.72%, respectively) in the presence of up to 90% of its degradation products. Determination was also successful when analyzing RCT in a formulation in the form of acetorphan packets. Results were statistically analyzed and found to be in accordance with those given by a reported method.