What Is the Difference between Glipizide and Glyburide?

The oral medications glipizide and glyburide are prescribed to treat type 2 diabetes. These drugs are second-generation members of the pharmaceutical class of sulfonylureas, which treat diabetes by stimulating pancreatic beta cells to release insulin and by helping the body use the insulin efficiently. The benefits of glipizide and glyburide are comparable as treatments — but not cures — for high blood sugar. The medications differ, however, in absorption, half-life and initial dosage for patients who have been newly diagnosed with type 2 diabetes. Both medications are available in oral tablets, but glipizide also is available in extended-release tablets.

The recommended initial dosage of glipizide is 5 milligrams per day. Taking glipizide with food slows its absorption. Its half-life is two to seven hours before it is eliminated from the body. Common side effects of glipizide include diarrhea, dizziness and rash. Serious side effects that require notification of a doctor include dark-colored urine, light-colored stool and yellowing of the eyes.

Glyburide's recommended initial dosage is 2.5-5.0 milligrams per day. Food does not affect the absorption of glyburide. The half-life of this medication is seven to 10 hours. Common side effects include nausea, rash and heartburn. Serious potential side effects include fever, facial swelling and unusual bleeding.

Both glipizide and glyburide have proved to be at least as effective as the first-generation sulfonylurea drugs chlorpropamide and tolbutamide. Only glipizide has shown the ability to be more effective than those medications, however. Glipizide and glyburide share potential counterindications with non-steroidal anti-inflammatory drugs (NSAIDs), hormone contraceptives, beta blockers and alcohol.

Type 1 diabetes cannot be treated with glipizide and glyburide. Although type 1 diabetes is caused by the body's inability to synthesize insulin, type 2 diabetes stems from the body improperly using the insulin that is produced. Glipizide and glyburide do not encourage the production of enough insulin to balance the lack caused by type 1 diabetes.