GLYNASE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for GLYNASE (GLYNASE).
Sulfonylurea that stimulates insulin secretion from pancreatic beta cells by blocking ATP-sensitive potassium channels, leading to membrane depolarization and calcium influx.
| Metabolism | Hepatic metabolism via CYP2C9 to inactive metabolites; minor renal excretion. |
| Excretion | Renal: approximately 50% as metabolites and unchanged drug; fecal/biliary: minor (less than 5% as unchanged drug). |
| Half-life | Terminal elimination half-life: 10-16 hours; clinical context: correlates with duration of glucose-lowering effect, prolonged in renal impairment. |
| Protein binding | >99% bound to serum proteins, primarily albumin. |
| Volume of Distribution | 0.12-0.15 L/kg; clinical meaning: relatively low Vd, indicating limited extravascular distribution. |
| Bioavailability | Oral: approximately 100% (completely absorbed). |
| Onset of Action | Oral: 30-60 minutes for reduction in blood glucose; peak effect at 2-4 hours. |
| Duration of Action | Oral: 12-24 hours; clinical notes: duration may extend up to 24 hours, caution in elderly and renal impairment due to risk of prolonged hypoglycemia. |
| Action Class | Sulfonylureas (Insulin Secretogogues) |
| Brand Substitutes | Glylup 5mg Tablet, Diacon 5mg Tablet, Glibetic 5mg Tablet, Glucotrol 5mg Tablet, Glipitis 5mg Tablet |
Initial dose 2.5-5 mg orally once daily with breakfast. Titrate by 2.5-5 mg weekly. Maximum dose 20 mg daily. Divided doses twice daily may be used for doses >10 mg.
| Dosage form | TABLET |
| Renal impairment | eGFR 30-60 mL/min: initiate at 2.5 mg daily, titrate cautiously. eGFR <30 mL/min: contraindicated. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B or C: avoid use due to risk of prolonged hypoglycemia. |
| Pediatric use | Not recommended for pediatric patients; safety and efficacy not established. |
| Geriatric use | Initial dose 2.5 mg daily. Titrate slowly to avoid hypoglycemia, monitor renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for GLYNASE (GLYNASE).
| Breastfeeding | Glyburide is excreted into breast milk in low amounts; the estimated infant dose is <1% of the maternal weight-adjusted dose, with an M/P ratio of approximately 0.06. It is generally considered compatible with breastfeeding, but infants should be monitored for hypoglycemia, especially if the mother is on high doses. |
| Teratogenic Risk | Glyburide (GLYNASE) is classified as FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, but adequate human studies in pregnant women are lacking. First trimester: No increased risk of major malformations reported. Second and third trimesters: May cause neonatal hypoglycemia and macrosomia; use with caution and monitor maternal glucose levels closely. |
■ FDA Black Box Warning
Increased risk of cardiovascular mortality compared to diet alone or diet plus insulin (based on the University Group Diabetes Program study).
| Serious Effects |
["Type 1 diabetes mellitus","Diabetic ketoacidosis","Known hypersensitivity to glyburide or sulfonylureas"]
| Precautions | ["May cause hypoglycemia, especially in elderly, debilitated, or malnourished patients","Increased cardiovascular mortality risk","May cause hemolytic anemia in patients with G6PD deficiency","Disulfiram-like reactions with alcohol"] |
| Food/Dietary | Avoid alcohol, which may cause disulfiram-like reaction and increase hypoglycemia risk. Take with breakfast to reduce gastrointestinal upset. Consistent meal timing is important to prevent hypoglycemia. No specific food-drug interactions but glucose monitoring around meals is advised. |
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| Fetal Monitoring | Monitor maternal blood glucose levels frequently (e.g., fasting and postprandial). Fetal surveillance includes serial ultrasound for growth assessment and amniotic fluid volume, nonstress test or biophysical profile in third trimester. Neonatal monitoring for hypoglycemia for at least 24 hours after delivery. |
| Fertility Effects | No known direct adverse effects on fertility in humans. Glyburide may improve fertility outcomes by optimizing glycemic control in diabetic women, as hyperglycemia can impair ovulation and increase miscarriage risk. |
| Clinical Pearls | Glyburide (GLYNASE) is a second-generation sulfonylurea with a longer half-life (10 hours) than glipizide, increasing hypoglycemia risk, especially in elderly or renally impaired patients. Avoid use in G6PD deficiency due to hemolytic anemia risk. Monitor for disulfiram-like reaction with alcohol. Use with caution in patients with hepatic impairment as glyburide is hepatically metabolized. Discontinue therapy if hypoglycemia persists despite dose adjustment. |
| Patient Advice | Take glyburide exactly as prescribed, usually once daily with breakfast or the first main meal. · Do not skip meals; this can increase the risk of low blood sugar (hypoglycemia). · Recognize symptoms of hypoglycemia (sweating, shakiness, confusion, hunger) and treat with 15 grams of rapid-acting sugar (e.g., 4 oz fruit juice, glucose tablets). · Avoid alcohol; it can cause severe hypoglycemia or a disulfiram-like reaction (flushing, nausea). · Inform all healthcare providers you are taking this medication, especially before surgery or diagnostic tests. · Monitor blood glucose regularly as directed and keep a log of results. · Report persistent high blood sugar or severe hypoglycemic episodes to your doctor. |