Cyclobenzaprine and promethazine?

My father has been suffering from diabetes for almost a decade. He has switched to shots from pills two years ago and it looks like his overall condition has worsened. His leg muscles are affected, he was diagnose with diabetic neuropathy and is taking cyclobenzaprine. Doctor also said that he might need promethazine also. What are these two drugs?

First one is used to deal with muscle spasms that are caused by various underlying conditions. In your fathers case it is diabetes. This drug, unfortunately, has many unwanted bad side effects that could complicate his life additionally. One of those is nausea, and promethazine can deal with that. Of course, it would be for best if he does not develop that particular symptom, then he would not have the need for an extra medication.