tolbutamide sodium

tolbutamide sodium Warning - High-alert drug!

Apo-Tolbutamide (CA), Novo-Butamide (CA)

Pharmacologic class: Sulfonylurea (first-generation)

Therapeutic class: Hypoglycemic

Pregnancy risk category C

Action

Stimulates insulin release from pancreatic beta cells. Increases peripheral tissue sensitivity to insulin, either by increasing the number of insulin receptors or enhancing insulin binding to cellular receptors.

Availability

Powder for injection: 1 g

Tablets: 500 mg

⊘Indications and dosages

➣ Adjunct in type 2 (non-insulin-dependent) diabetes mellitus not controlled by diet and exercise

Adults: Initially, 1 to 2 g P.O. daily. May adjust to maintenance dosage of 250 mg to 2 g P.O. daily; maximum dosage is 3 g daily.

➣ To aid diagnosis of pancreatic islet cell adenoma

Adults: 1g I.V.

Dosage adjustment

• Hepatic insufficiency

Contraindications

• Hypersensitivity to drug, its components, or other sulfonylureas
• Diabetic coma or ketoacidosis
• Sole therapy for type 1 (insulin-dependent) diabetes mellitus

Precautions

Use cautiously in:
• severe renal or hepatic disease
• stress caused by infection, fever, trauma, or surgery
• pregnant or breastfeeding patients (use not recommended)
• children (safety and efficacy not established).

Administration

• Give oral doses as prescribed, either as a single dose in morning or in divided doses after meals (based on GI tolerance).
• When giving I.V. to aid diagnosis of pancreatic islet cell adenoma, expect blood glucose level to fall rapidly for 30 to 45 minutes, followed by rise to normal level in next 90 to 180 minutes. In patients with insulinomas, blood glucose decrease typically has greater magnitude and longer duration than in healthy persons.

Route	Onset	Peak	Duration
P.O.	1 hr	3-4 hr	6-12 hr
I.V.	Rapid	20 min	Unknown

Adverse reactions

CNS: malaise, paresthesia, vertigo, headache, fatigue, dizziness

CV: increased risk of cardiovascular mortality

GI: nausea, heartburn, epigastric fullness

Metabolic: syndrome of inappropriate antidiuretic hormone secretion, severe hypoglycemia

Skin: transient rash, pruritus, erythema, urticaria, photosensitivity

Other: taste alteration, weight gain

Interactions

Drug-drug. Androgens, anticoagulants, azole antifungals, chloramphenicol, clofibrate, fenfluramine, fluconazole, gemfibrozil, histamine₂ antagonists, magnesium salts, methyldopa, MAO inhibitors, phenylbutazone, probenecid, salicylates, sulfonamides, tricyclic antidepressants, urinary acidifiers: increased hypoglycemia

Beta-adrenergic blockers, calcium channel blockers, cholestyramine, corticosteroids, diazoxide, estrogens, hormonal contraceptives, hydantoins, isoniazid, nicotinic acid, phenothiazines, rifampin, sympathomimetics, thiazide diuretics, thyroid agents, urinary alkalizers: decreased hypoglycemic effect

Charcoal: decreased tolbutamide absorption

Digoxin: increased digoxin blood level and risk of toxicity

Drug-diagnostic tests. Glucose: decreased level

Radioactive iodine: decreased thyroid uptake

Urine albumin: false-positive reaction

Drug-herbs. Aloe, bitter melon, fenugreek, St. John's wort: increased risk of hypoglycemia

Drug-behaviors. Alcohol use: disulfiram-like effect

Patient monitoring

• Monitor blood glucose level frequently.
• Assess vital signs and cardiovascular and neurologic status.
• Monitor nutritional status; report significant problems.

Patient teaching

• Tell patient to take as prescribed, either as a single dose in morning or in divided doses after meals.
• Stress importance of adhering to prescribed diet and exercise.
• Advise patient to report significant adverse reactions.
• Instruct patient to monitor blood glucose level carefully.
• Caution patient not to drink alcohol.
• Tell patient some herbs affect blood glucose level. Advise him to consult prescriber before using.
• Teach patient effective ways to counteract photosensitivity.
• Tell patient he'll undergo regular blood testing during therapy.
• Advise female patient that drug isn't recommended during pregnancy or breastfeeding.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.