Detailed Drug Information:

DRUG CLASS AND MECHANISM: Acetohexamide, chlorpropamide, tolazamide and tolbutamide are oral blood sugar-lowering drugs in a class of medications for diabetes called sulfonylureas. They were the first four sulfonylureas to be used to manage type II diabetes and are commonly referred to as first generation sulfonylureas. The second generation sulfonylureas are glipizide (Glucotrol, Glucotrol XL), glyburide (Micronase), and glimepiride (Amaryl). The primary difference between the first and second generation sulfonylureas is in the way they are eliminated from the body. As a result, second generation sulfonylureas usually are taken less frequently each day than first generation sulfonylureas and generally are preferred when there is poor function of the kidneys. The second generation sulfonylureas were first used in the United States in 1984.

All sulfonylureas lower blood sugar (glucose) by increasing the release of insulin from the pancreas. (Insulin is the hormone that lowers the blood sugar level.)

Approximately 90% of patients with diabetes have type II diabetes, formerly called non-insulin-dependent diabetes mellitus. Type II diabetes usually occurs in adults and is associated with obesity and a strong family history of diabetes. The inability to control blood glucose in type II diabetes is caused by reduced insulin release by the pancreas as well as decreased removal of glucose from the blood by the body's cells.

PREPARATIONS: Tablets: Acetohexamide, 250 or 500 mg; chlorpropamide (Diabinese), 100 or 250 mg; (Tolinase), 100, 250 or 500 mg; and tolbutamide (Orinase), 500 mg.

STORAGE: All sulfonylureas should be stored at room temperature, 15-30°C(59-86°F) in an air-tight container.

PRESCRIBED FOR: It is believed that strict glucose control in diabetics reduces the chances of eye, kidney, and nerve damage. The first generation sulfonylureas are used in type II diabetes to help lower and control blood glucose that is not controlled by diet and exercise. They are usually tried before turning to insulin for therapy.

DOSING: Like other medications used to manage diabetes, the dose of the first generation sulfonylureas should be individualized using periodic measurements of blood glucose. Any of the first generation sulfonylureas may be taken with food, although tolbutamide is more effective if taken 30 minutes before a meal.

All sulfonylureas can lower glucose levels to the point of causing symptoms and signs (hypoglycemia). Therefore, these agents must be used carefully with patients who have other physical or medical factors that may lower their blood glucose. These factors include kidney or liver disease, poor food intake, alcohol use, or participation in heavy exercise.

DRUG INTERACTIONS: Drugs that may interact with the first generation sulfonylureas and increase the risk of hypoglycemia include blood thinning agents(Coumadin), chloramphenicol (Ak-Chlor), clofibrate (Atromid), alcohol, MAO inhibitors including tranylcypromine(Parnate), non-steroidal anti-inflammatory drugs including ibuprofen (Motrin), aspirin, sulfinpyrazone (Anturane), sulfonamides including sulfamethoxazole (Gantanol), phenylbutazone (Azolid), and drugs that make urine more acidic including ammonium chloride.

Drugs that may interact with the first generation sulfonylureas and reduce their hypoglycemic effect include diazoxide(Proglycem), rifampin (Rifadin), diuretics including hydrochlorothiazide (Hydrodiuril) and furosemide (Lasix), and drugs that make urine more basic including sodium bicarbonate (Neut).

Alcohol may interact with the first generation sulfonylureas, especially chlorpropamide, to cause moderate to severe facial flushing (increased flow of blood to the face) and an increase in facial temperature.

Chlorpropamide may prolong the action of barbiturates including phenobarbital. Probenecid (Benemid) may increase the hypoglycemic effect of chlorpropamide. Blood levels of digoxin (Lanoxin) may be increased by sulfonylureas, and, therefore, digoxin should be used cautiously with chlorpropamide and other first generation sulfonylureas.

Beta-blocking drugs including propranolol (Inderal) may interact with the first generation sulfonylureas, especially tolbutamide. Beta-blockers may lower or increase glucose levels when used alone. When used with sulfonylureas, beta-blocking drugs may interfere with glucose lowering by the sulfonylureas. In addition, beta-blockers can blunt some of the body's protective responses to hypoglycemia, for example, increased heart rate, thus making it difficult for patients to recognize hypoglycemia. This notwithstanding, beta-blockers have been used successfully in diabetic patients and have been associated with improved survival in diabetics with high blood pressure.