I concur with trolleater, call your husbands doctor for clarification and inform the doctor of your husbands discomfort with Glipizide. He/she should never changed medications w/o first informing your husband and explaining the reason why.
I'm unsure on the dosage equivalency of Glipizide vs Glyburide. Both are in the same class of diabetes medications but Glipizide is short/rapid acting while Glyburide is slow/long acting. If your husbands fasting blood sugar levels are elevating it may be the reason for the change. Good luck -
YES, call the Dr., your Pharmacist can also tell you if there are changes in the meds, but call Dr. asap and let him know what is going on.