TOLBUTamide

General

High Alert Medication: This medication bears a heightened risk of causing significant patient harm when it is used in error.

Pronunciation
tole-BYOO-ta-mide [Pronunciation]

Trade Name(s)

• Apo-Tolbutamide [Canada]

• Mobenol [Canada]

• Novo-Butamide [Canada]

• Orinase

• Tol-Tab

Indications

• PO: Control of blood sugar in type 2 diabetes mellitus when diet therapy fails. Requires some pancreatic function.

• IV: Diagnosis of pancreatic islet cell adenomas.

Action

• Lowers blood sugar by stimulating the release of insulin from the pancreas and increasing the sensitivity to insulin at receptor sites.

• May also decrease hepatic glucose production.

• Lowering of blood sugar in diabetic patients.

• Pronounced and prolonged hypoglycemic effect diagnostic of pancreatic islet cell adenoma.

Pharmacokinetics

Absorption: Well absorbed following oral administration; IV administration results in complete bioavailability.

Distribution: Unknown.

Protein Binding: 96%.

Metabolism and Excretion: Mostly metabolized by the liver.

Half-life: 7 hr (range 4–25 hr).

TIME/ACTION PROFILE (hypoglycemic activity)

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity (cross-sensitivity with sulfonamides may occur);

• Type 1 diabetes;

• Diabetic coma or ketoacidosis;

• Severe renal, hepatic, thyroid, or other endocrine disease;

• Uncontrolled infection, serious burns, or trauma.

• Severe cardiovascular disease;

• Geriatric patients (increased sensitivity; dosage reduction may be required);

• Hepatic or renal impairment (increased risk of hypoglycemia);

• Infection, stress, or changes in diet may alter requirements for control of blood sugar;

• Impaired thyroid, pituitary, or adrenal function;

• Malnutrition, high fever, prolonged nausea, or vomiting;

• Pregnancy or lactation (safety not established; insulin recommended during pregnancy).

Adverse Reactions/Side Effects

CNS: dizziness, drowsiness, headache, weakness.

GI: constipation, cramps, diarrhea, drug-induced hepatitis, heartburn, increased appetite, nausea, vomiting.

Derm: photosensitivity, rashes.

Endo: hypoglycemia.

F and E: hyponatremia.

Hemat: APLASTIC ANEMIA, agranulocytosis, leukopenia, pancytopenia, thrombocytopenia.

*CAPITALS indicates life-threatening.
*italic indicates most frequent.

Interactions

Drug-Drug

• Ingestion of alcohol may result in disulfiram-like reaction.

• Effectiveness may be decreased by concurrent use of diuretics , corticosteroids , phenothiazines , hormonal contraceptives , estrogens , thyroid preparations , phenytoin , nicotinic acid , sympathomimetics , and isoniazid .

• Alcohol , androgens (testosterone) , chloramphenicol , clofibrate , MAO inhibitors , NSAIDs (except diclofenac), salicylates , and sulfonamides may increase the risk of hypoglycemia.

• Concurrent use with warfarin may alter the response to both agents (increased effects of both initially, then decreased activity; close monitoring recommended during any changes in dosage).

• Beta blockers may mask the signs and symptoms of hypoglycemia.

• Glucosamine may worsen blood glucose control.

• Fenugreek , chromium , and coenzyme Q-10 may produce additive hypoglycemic effects.

Route/Dosage

• PO (Adults): 1000–2000 mg/day in single or divided doses; then adjusted to maintanance dose of 250–2000 mg/day (some patients may require up to 3000 mg/day)..

• IV (Adults): 1 g as part of the Fajan test..

Availability

• Tablets: 500 mg

• Powder for injection: 1 g with 20 mL diluent

Assessment

• Observe patient for signs and symptoms of hypoglycemic reactions (sweating, hunger, weakness, dizziness, tremor, tachycardia, anxiety). Patients on concurrent beta-blocker therapy may have very subtle signs and symptoms of hypoglycemia.

• Assess patient for allergy to sulfonamides.

• Monitor intake and output ratios and daily weight. Notify physician or other health care professional promptly if peripheral edema, rales/crackles, or a significant discrepancy in totals develops.

• Serum glucose and hemoglobin A1C should be monitored periodically throughout therapy to evaluate effectiveness of treatment.

» Monitor CBC periodically throughout therapy. Notify physician or other health care professional promptly if decrease in blood counts occurs.

» May cause an increase in AST, LDH, BUN, and serum creatinine.

• Overdose is manifested by symptoms of hypoglycemia. Mild hypoglycemia may be treated with administration of oral glucose. Severe hypoglycemia should be treated with IV D50W followed by continuous IV infusion of more dilute dextrose solution at a rate sufficient to keep serum glucose at approximately 100 mg/dL.

Potential Nursing Diagnoses

• Imbalanced nutrition: more than body requirements (Indications)

• Noncompliance (Patient/Family Teaching)

Implementation

• High Alert: Accidental administration of oral hypoglycemic agents to non-diabetic adults and children has resulted in serious harm or death. Before administering, confirm that patient has Type 2 diabetes. Do not confuse tolbutamide with tolazamide.

• Patients stabilized on a diabetic regimen who are exposed to stress, fever, trauma, infection, or surgery may require administration of insulin.

» To convert from other oral hypoglycemic agents or insulin dosage of <20 units/day, change can be made without gradual dosage adjustment. Patients taking 20–40 units/day should convert gradually by receiving oral hypoglycemic agent and a 25–50% reduction in insulin dose the 1st day, with gradual insulin dosage reduction as tolerated. Patients taking >40 units/day should use a 20–50% reduction in insulin dose the 1st day, with gradual insulin dosage adjustment as tolerated. Monitor serum glucose and urine ketones at least 3 times/day during conversion.

• PO: May be administered once in the morning or divided into 2 doses. Administer with meals to ensure best diabetic control and minimize gastric irritation. Do not administer after last meal of the day.

» Tablets may be crushed and taken with fluids if patient has difficulty swallowing.

Patient/Family Teaching

• Instruct patient to take medication at same time each day. If a dose is missed, take as soon as remembered unless almost time for next dose. Do not take if unable to eat.

• Explain to patient that this medication controls hyperglycemia but does not cure diabetes. Therapy is long-term.

• Review signs of hypoglycemia and hyperglycemia with patient. If hypoglycemia occurs, advise patient to drink a glass of orange juice or ingest 2–3 tsp of sugar, honey, or corn syrup dissolved in water or an appropriate number of glucose tablets and notify health care professional.

• Encourage patient to follow prescribed diet, medication, and exercise regimen to prevent hypoglycemic or hyperglycemic episodes.

• Instruct patient in proper testing of serum glucose and urine ketones. These tests should be closely monitored during periods of stress or illness and health care professional notified if significant changes occur.

• May occasionally cause dizziness or drowsiness. Caution patient to avoid driving or other activities requiring alertness until response to medication is known.

• Caution patient to avoid other medications, especially aspirin and alcohol, while on this therapy without consulting health care professional.

• Concurrent use of alcohol may cause a disulfiram-like reaction (abdominal cramps, nausea, flushing, headaches, and hypoglycemia).

• Insulin is the recommended method of controlling blood sugar during pregnancy. Counsel female patients to use a form of contraception other than oral contraceptives and to notify health care professional promptly if pregnancy is planned or suspected.

• Caution patient to use sunscreen and protective clothing to prevent photosensitivity reactions.

• Advise patient to inform health care professional of medication regimen prior to treatment or surgery.

• Advise patient to carry a form of sugar (sugar packets, candy) and identification at all times describing disease process and medication regimen.

• Advise patient to notify health care professional promptly if unusual weight gain, swelling of ankles, drowsiness, shortness of breath, muscle cramps, weakness, sore throat, rash, or unusual bleeding or bruising occurs.

• Emphasize the importance of routine follow-up exams.

Evaluation/Desired Outcomes

Control of blood glucose levels without hypoglycemic episodes.