Classifications: hormone; sulfonylurea antidiabetic;
Therapeutic: antidiabetic, sulfonylurea

Prototype: Glyburide
Pregnancy Category: C


100 mg, 250 mg, 500 mg tablets


Orally effective sulfonylurea hypoglycemic structurally and pharmacologically related to tolbutamide but about 5 times more potent. Lowers blood glucose primarily by stimulating pancreatic beta cells to secrete insulin.

Therapeutic Effect

Antidiabetic action is a result of stimulation of the pancreas to secrete more insulin in the presence of blood sugar; it requires functioning beta cells.


Mild to moderately severe type 2 diabetes mellitus that cannot be controlled by diet and weight reduction and that is uncomplicated by acidosis, ketosis, coma. Effective in primary or secondary failures to other sulfonylurea


Known sensitivity to sulfonylureas and to sulfonamides; type 1 diabetes complicated by ketoacidosis; infection; trauma; pregnancy (category C). Safety in lactation or children is not established.

Cautious Use

Older adults; renal disease; renal failure, renal impairment.

Route & Dosage

Type 2 Diabetes Mellitus
Adult: PO 100 mg–1 g q.d. to b.i.d. a.c., may adjust dose by 100–250 mg/d at weekly intervals (max: 1 g/d)


  • Give in the morning with or before meals.
  • Divide dose of more than 500 mg and give b.i.d.
  • Crush tablet if patient is unable to swallow it whole. Be sure to give with an allowable fluid, not dry.
  • Store at 15°–30° C (59°–86° F) in a tightly closed container unless otherwise directed. Keep drug out of the reach of children.

Adverse Effects (≥1%)

GI: Nausea, vomiting, cholestatic jaundice. Metabolic: Hypoglycemia. CNS: Vertigo. Skin: Photosensitivity. Hematologic: Agranulocytosis.


Drug: Alcohol elicits disulfiram-type reaction in some patients; oral anticoagulants, chloramphenicol, clofibrate, phenylbutazone, mao inhibitors, salicylates, probenecid, sulfonamides may potentiate hypoglycemic actions; thiazides may antagonize hypoglycemic effects; cimetidine may increase tolazamide levels, causing hypoglycemia. Herbal: Ginseng, karela may potentiate hypoglycemic effects.


Absorption: Slowly from GI tract. Onset: 60 min. Peak: 4–6 h. Duration: 10–15 h (up to 20 h in some patients). Distribution: Distributed in highest concentrations in liver, kidneys, and intestines; crosses placenta; distributed into breast milk. Metabolism: Extensively in liver. Elimination: 85% in urine, 15% in feces. Half-Life: 7 h.

Nursing Implications

Assessment & Drug Effects

  • Be aware that reduction of dose frequently alleviates most mild to moderately severe hypoglycemic symptoms.
  • Observe patients with a history of ketoacidosis or coma closely, especially during the early adjustment period.

Patient & Family Education

  • Check blood glucose and urine daily for sugar and acetone. Important to continue close medical supervision for first 6 wk of treatment.
  • Be aware that doses >1000 mg/d rarely provide improvement in diabetic control.
  • Do not take OTC preparations unless approved or prescribed by physician.
  • Understand that alcohol can precipitate a disulfiram-type reaction.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2023 Last Updated On: 01/28/2023 (0)
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