- Have been taking within 4 weeks of screening any prescription or over-the-counter (OTC) medication that significantly affects glucose metabolism, including but not limited to, sulfonylureas, meglitinides, biguanides, thiazolidinediones, alpha-glucosidase inhibitors, Inhibitors of dipeptidyl peptidase 4 (DPP-4 inhibitors), systemic corticosteroids