What Causes Difficulty In Walking Along With Slurred Speech While On Tancodep?

My mother aged 78 has been prescribed tancodep for depression behaviour. She was moving around on her own with a walker before that. But thereafter she is not even getting up from the bed, is scared to put her feet on the ground and bends them when we try to help her up & to walk. Her speech is also becoming slurred. what is your view ? whal will be the effect we stop and give restyl 0.25 mg ?