They split into first-generation and second-generation. First-generation use is fading: newer agents work better and these older drugs are now thought to possibly raise cardiovascular death. Second-generation agents win on safety. They clear through urine and bile (safer in renal dysfunction), do not fight with many protein-bound drugs, and last longer.
Generic and Brand Names
First-generation: chlorpropamide (Diabinese), tolazamide (Tolinase), tolbutamide (Orinase).
Second-generation: glimepiride (Amaryl), glipizide (Glucotrol), glyburide (Diabeta, Micronase).
Therapeutic Action
Sulfonylureas stimulate insulin release from the beta cells in the pancreas. They also improve insulin binding to receptors and may increase the number of receptors. On top of that, they boost the effect of antidiuretic hormone on renal cells.
Indications
Adjunct to diet and exercise for type 2 diabetes in patients older than 10 years of age. The extended-release form is for patients older than 17 years of age. Also used as adjunct treatment in polycystic ovary syndrome.
Pharmacokinetics
Here are the characteristic interactions of sulfonylureas and the body in terms of absorption, distribution, metabolism, and excretion:
| Route | Onset | Peak | Duration |
|---|---|---|---|
| Oral | Slow | 2-2.5 h | 10-16 h |
| Half-life (T1/2) | Metabolism | Excretion |
|---|---|---|
| 6.2-17 h | Liver | Urine |
Contraindications and Cautions
Allergy to sulfonylureas (risk of hypersensitivity). Type 1 diabetes, where there are no functioning beta cells and the drug does nothing. Pregnancy and lactation, given the risk to fetus or neonate.
Adverse Effects
Hypoglycemia is the most common, and it can be severe (FDA glipizide labeling). The ADA Standards of Care group sulfonylureas with insulin and meglitinides as the higher-hypoglycemia-risk agents and recommend reassessing the dose whenever a new glucose-lowering drug is started. Also GI distress (nausea, vomiting, epigastric discomfort) and allergic skin reactions.
Interactions
Drugs that acidify the urine decrease sulfonylurea excretion, raising drug levels.
Nursing Considerations
Assessment
Screen for the contraindications and cautions: allergy history, pregnancy and lactation status, severe renal or hepatic dysfunction. Get a baseline physical before therapy so you can track effectiveness and adverse effects against it. Check orientation and reflexes, baseline pulse and blood pressure, breath sounds, and abdominal sounds and function, since altered glucose shows up across these systems. Review nutritional intake and adherence to the prescribed diet, and assess activity and exercise level, which shift serum glucose and dosing needs. Monitor blood glucose as ordered, plus urinalysis for glycosuria and renal and liver function tests to catch the need for dose changes or signs of toxicity.
Nursing Diagnoses
Risk for unstable blood glucose related to ineffective dosing. Imbalanced nutrition, less than body requirements, related to metabolic effects. Disturbed sensory perception (kinesthetic, visual, auditory, tactile) related to glucose levels.
Implementation
Time the dose to meals so it works. Make sure the patient has a diet and exercise plan and good hygiene to improve insulin effectiveness and cut disease complications. Monitor nutritional status and arrange a consult as needed. Blood glucose monitoring is the best read on the dose, so obtain levels as ordered. During trauma, pregnancy, or severe stress, switch the patient to insulin coverage. Teach drug effects and the warning signs to report.
Evaluation
Look for stable blood glucose, no hypoglycemia or GI distress, and a patient who can name the drug, its indication, and the adverse effects to watch for. Confirm adherence to therapy.
Frequently Asked Questions
How do sulfonylureas lower blood glucose? They stimulate the beta cells of the pancreas to release more insulin, so they only work when functioning beta cells remain. They also improve insulin binding at its receptors.
Why are sulfonylureas not used for type 1 diabetes? Type 1 diabetes leaves no functioning beta cells for the drug to act on, so it does nothing. FDA labeling states sulfonylureas are not for type 1 diabetes or diabetic ketoacidosis.
What is the main side effect to watch for? Hypoglycemia, which can be severe. The ADA Standards of Care classify sulfonylureas among the higher-risk agents for low blood sugar and advise reassessing the dose when other glucose-lowering drugs are added.
What is the difference between first and second generation sulfonylureas? First-generation agents (chlorpropamide, tolazamide, tolbutamide) are used less today and may raise cardiovascular risk. Second-generation agents (glimepiride, glipizide, glyburide) are safer, longer-acting, and interact with fewer protein-bound drugs.
When should a patient be switched from a sulfonylurea to insulin? During trauma, pregnancy, or severe physiologic stress, insulin coverage is used because glucose control becomes unpredictable.
When is glipizide taken? Per FDA labeling, the extended-release form is taken once daily with breakfast or the first main meal; timing the dose to meals helps it work and limits hypoglycemia.