Reaction to Glyco-Flex1?

My little yorkie, Jenny who's 12 years old was recently prescribed Glyco-Flex1for some stiffness in her back legs. Firstly it's almost impossible to get her to take it, secondly when she does she seems extremely restless in the evening, drinking constantly and not settling and then she's padding around in the night not sleeping and because she drank so much wanting to go out constantly. Stopped the medication for a couple of days and she seems back to normal (complete with stiff legs!) Has anyone else had this reaction to Glyco-Flex1. Jenny weighs about approx 2.5lbs. and was prescribed half a tablet once a day.