Medication Update


South Med J. 2002;95(1) 

In This Article


Mode of Action

Sulfonylureas increase pancreatic beta cell insulin secretion. Glimepiride may increase peripheral tissue insulin sensitivity.


Known hypersensitivity to the particular sulfonylurea or components in their formulation. Sulfonylureas should generally be avoided in pregnancy. Pregnancy Category: C. Glynase and Micronase are Pregnancy Category B.

Adverse Effects

Blood dyscrasias (aplastic anemia, hemolytic anemia, leukopenia, pancytopenia, thrombocytopenia), dizziness, drowsiness, headache, possible increase in cardiovascular mortality in patients treated with tolbutamide, gastrointestinal effects, hypoglycemia, syndrome of inappropriate secretion of antidiuretic hormone, various skin reactions.

Drug-Drug Interactions

The following drugs may increase the effectiveness of the sulfonylureas, resulting in hypoglycemia: androgens, anticoagulants, azole antifungals, chloramphenicol, ciprofloxacin (with glyburide), clofibrate, fenfluramine, fluconazole, gemfibrozil, H2 antagonists, magnesium salts, methyldopa, monoamine oxidase inhibitors, probenecid, salicylates, sulfinpyrazone, sulfonamides, tricyclic antidepressants, and urinary acidifiers.

The following drugs may decrease the effectiveness of the sulfonylureas, resulting in hyperglycemia: beta blockers, calcium channel blockers, cholestyramine, corticosteroids, diazoxide, estrogens, hydantoins, isoniazid, nicotinic acid, oral contraceptives, phenothiazines, rifampin, sympathomimetics, thiazide diuretics, thyroid medications, and urinary alkalinizers.

Drug-Food Interactions

Absorption of glipizide is delayed by food. Other sulfonylureas may be taken with or without food.

Products Available

  • Acetohexamide (Dymelor): Starting doses, 250-1,500 mg/day. Usual dose range, 250-1,500 mg/day (divide doses >1,000 mg/day). Dosage forms available, 250 mg and 500 mg tablets.

  • Chlorpropamide (Diabinese): 250 mg QD (100-125 mg QD in elderly or in patients with impaired hepatic/renal function). Usual dose range, 100-500 mg/day. Dosage forms available, 100 mg and 250 mg tablets.

  • Glimepiride (Amaryl): Starting doses, 1-2 mg QD with breakfast. Usual dose range, 1-8 mg QD. Dosage forms available, 1 mg, 2 mg, and 4 mg tablets.

  • Glipizide (Glucotrol, Glucotrol XL): Starting doses 5 mg QD, 30 minutes before breakfast. Usual dose range, 5-40 mg/day (single or divided doses); 5-20 mg/day for the extended release formulation. Dosage forms available, 5 mg and 10 mg immediate release and extended release tablets.

  • Glyburide (DiaBeta, Micronase, Glynase PresTab): Starting doses, Nonmicronized - 2.5-5 mg QD with breakfast. Micronized - 1.5-3 mg QD with breakfast. Usual dose range, Nonmicronized - 1.25-20 mg/day (single or divided doses); Micronized - 0.75-12 mg/day (divide doses >6mg/day). Dosage forms available, 1.25 mg, 2.5 mg, and 5 mg tablets; 1.5 mg, 3 mg, and 6 mg micronized tablets.

  • Tolazamide (Tolinase): Starting doses, 100-250 mg/day. Usual dose range, 100-1,000 mg/day (divide doses >500 mg/day). Dosage forms available, 100 mg, 250 mg, and 500 mg tablets.

  • Tolbutamide (Orinase): Starting doses, 1-2 g/day (single or divided doses). Usual dose range, 0.25-3 g/day. Dosage forms available, 500 mg tablets.

Other Points of Interest

Patients taking chlorpropamide may experience a disulfiram-like reaction (usually facial flushing and/or breathlessness) if they consume alcohol while they are on the medication.


  • Hutchison TA, Shahan DR, Anderson ML (eds): DRUGDEX System. MICROMEDEX, Inc, Englewood, Colo. (Edition expires 12/2000)

  • Hebel SK, Katstrup EK (eds): Drug Facts and Comparisons. St. Louis, Mo. 2001


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