A valid HPLC method for monitoring the hydrolytic degradation of methocarbamol in the presence of various cyclodextrins detection of a new degradation product
Michaleas, Sotiris G.
Antoniadou -Vyza, Ekaterini A.
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β-Cyclodextrins (CD) are naturally occurring cyclic oligosaccharides composed of seven D-glucose units linked head to tail with α, 1-4 linkages. They form a relatively inflexible structure in which the outside of the ring bears the hydrophilic hydroxyl groups while the internal cavity is rather hydrophobic. Improving the drug stability, solubility and bioavailability by the formation of drug CD inclusion complexes is a well-known process. For facing stability and solubility problems of the muscle relaxant drug Methocarbamol (ML) inclusion complexes of this hydrophobic drug with CDs were prepared. The degradation kinetic study of ML, in the presence of CDs, under pH 7.4 at 37 °C showed that a new degradation product was present. A new HPLC stability indicating method was developed to separate, the appeared, new product and determinate ML in the presence of all its degradation products and CD. The stability studies and the determination of the degradation rate constant (k values) of ML hydrolytic reactions were carried out in different temperatures ranging from 37 to 60 °C. Further studies in close pH values were also performed to estimate the limits within the new compound is formed.