Studies On Gabapentin Hydrochloride Sustained-Release Tablets

Gabapentin is a neuroprotective agent with antiepileptic properties. The structure is small, zwitterionic, andresembles an amino.Gabapentin hydrochloride(GBP-HCl) is its hydrochloric salt.A selective and sensitive method was developed for the determination of GBP-HCl during the study of release.The method is based on the condensation of the drug through their amino group with acetylacetone and formaldehyde according to Hantzsch reaction yielding a yellowish-orange color derivative which can be measured spectrophotometrically at 415nm.We also developed a HPLC method for the determination of the drug content of the tablet and the preformulation study.The physicalchemical properties of GBP-HCl were investigated. Temperature,moisture and light had little effect on the chemical stability of solid GBP-HCl. GBP-HCl can be easily dissolved in water and other ralease medium,whose solubility is more than 100mg/ml.The pKa was determination by titration,at37℃,pKa1,pKa2 and pI are 3.17,9.39and 6.28 respectively.Appearant oil-water partition coefficient was very low at different pH value,which indicates that the drug has high polarity.The water uptake and erosion behaviour of hydrophilic material were investigated. 1.The high viscosity grades of HPMC(K4M,K15M and K100M) have the similar uptake of water,and the water uptake of low viscosity grade of HPMC(METHOCEL 100LV) is lower than the high viscosity grades.The water uptake of CMCNa and Carbomer971 is higher than HPMC material.2. Every viscosity grade of HPMC has obviously difference on erosion .CMCNa...