Tolbutamide
Pronouncation: (tole-BYOO-tuh-mide)Class: Sulfonylurea
Trade Names:
Orinase
- Tablets 500 mg
Trade Names:
Orinase Diagnostic
- Powder for injection 1 g (as sodium)/vial
Novo-Butamide (Canada)
Pharmacology
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Decreases blood glucose by stimulating release of insulin from pancreas.
Pharmacokinetics
Absorption
Orally administered tolbutamide is readily absorbed from the GI tract.
Metabolism
Tolbutamide has no p-amino group, cannot be acetylated; however, presence of p-methyl group makes it susceptible to oxidation. A major metabolite is 1-butyl-3-p-carboxy-phenylsulfonylurea (inactive).
Elimination
Tolbutamide t ½ is 4.5 to 6.5 h.
Onset
Onset of action is 20 min.
Peak
Time to peak effect is 3 to 4 h.
Duration
Tolbutamide duration of action is 24 h.
Indications and Usage
Oral formAdjunct to diet to lower blood glucose in patients with non-insulin-dependent diabetes mellitus (type 2) whose hyperglycemia cannot be controlled by diet alone.
IV form (tolbutamide sodium)Aid in diagnosis of pancreatic islet cell adenoma.
Contraindications
Hypersensitivity to sulfonylureas; diabetes complicated by ketoacidosis with or without coma; sole therapy of insulin-dependent (type 1) diabetes mellitus; diabetes occurring during pregnancy.
Dosage and Administration
AdultsPO Usually 1 to 2 g/day (range, 0.25 to 3 g) in 1 to 2 divided doses.
For Diagnostic PurposesAdults
IV 1 g over 2 to 3 min.
Drug Interactions
Androgens, anticoagulants, azole antifungals, chloramphenicol, clofibrate, dicumarol, fenfluramine, fluconazole, gemfibrozil, histamine H 2 antagonists, magnesium salts, methyldopa, MAOIs, phenylbutazone, probenecid, salicylates, sulfinpyrazone, sulfonamides, tricyclic antidepressants, urinary acidifiersMay increase hypoglycemic effect.
Beta-blockers, calcium channel blockers, cholestyramine, corticosteroids, diazoxide, estrogens, hydantoins, isoniazid, nicotinic acid, oral contraceptives, phenothiazines, rifampin, sympathomimetics, thiazide diuretics, thyroid agents, urinary alkalinizersMay decrease hypoglycemic effect.
CharcoalCharcoal can reduce the absorption of sulfonylureas; depending on the clinical situation, this will reduce their efficacy or toxicity.
Digitalis glycosidesCoadministration may result in increased digitalis serum levels.
DigoxinMay cause increased digoxin serum concentrations.
EthanolMay cause disulfiram-like reaction.
Laboratory Test Interactions
Drug may cause false-positive reaction for albumin with acidification-after-boiling test; no interference occurs with sulfosalicyclic acid test. Elevated LFTs and elevations in BUN and creatinine may occur.
Adverse Reactions
Cardiovascular
Increased risk of cardiovascular mortality.
CNS
Dizziness; vertigo.
Dermatologic
Allergic skin reactions; eczema; pruritus; erythema; urticaria; morbilliform or maculopapular eruptions; lichenoid reactions; porphyria; photosensitivity.
EENT
Tinnitus.
GI
Nausea; epigastric fullness; heartburn.
Hematologic
Leukopenia; thrombocytopenia; aplastic anemia; agranulocytosis; hemolytic anemia; pancytopenia.
Hepatic
Cholestatic jaundice.
Metabolic
Hypoglycemia; SIADH with water retention and dilutional hyponatremia, especially in patients with CHF or hepatic cirrhosis.
Miscellaneous
Disulfiram-like reaction; weakness; paresthesia; fatigue; malaise; slight burning sensation along course of vein during IV injection; thrombophlebitis with thrombosis of injected vein.
Precautions
Pregnancy
Category C . Insulin is recommended to control elevated blood glucose levels during pregnancy.
Lactation
Excreted into breast milk.
Children
Safety and efficacy have not been established.
Elderly
Particularly susceptible to hypoglycemic action. Hypoglycemia may be difficult to recognize in elderly.
Renal Function
Use drug with caution.
Hepatic Function
Use drug with caution.
Disulfiram-like syndrome
Administration of drug with alcohol may induce facial flushing and breathlessness.
Cardiovascular risk
Patients treated for 5 to 8ߙyr with diet plus tolbutamide (1.5 g/day) had a rate of cardiovascular mortality approximately 2.5ߙtimes that of patients treated with diet alone.
Overdosage
Symptoms
Hypoglycemia including symptoms of the following: tingling of lips and tongue, nausea, lethargy, confusion, agitation, nervousness, tachycardia, sweating, tremor, hunger, convulsions, stupor, coma.
Patient Information
- Instruct patient to follow the diet and exercise regimen prescribed by health care provider.
- Inform patient of symptoms of and treatment for low blood sugar and advise patient to carry source of sugar at all times.
- Instruct patient to avoid alcohol. Inform patient that alcohol may react with tolbutamide and cause Antabuse -like reaction (eg, flushing, headache, dizziness, high BP).
- Instruct patient to monitor weight and to inform health care provider if steady weight gain occurs.
- Inform patient that surgery, illness, or trauma may require temporary use of insulin.
- Instruct patient to alert health care provider to following problems: nausea, vomiting, GI distress, diarrhea, fever, sore throat, rash, itching, weakness, unusual bruising or bleeding, spilling of glucose or ketones in urine.
- Caution patient to avoid exposure to sunlight and to use sunscreen or wear protective clothing to avoid photosensitivity reaction.
- Recommended that patient carry medical identification (eg, card, bracelet) indicating condition and drug therapy.
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More Tolbutamide resources:
Tolbutamide - Includes detailed dosage instructions.
