Adult: Initially, 1-2 g daily as a single dose in the morning or in divided doses. Maintenance: 0.25-2 g daily. Max: 3 g daily. Elderly: Initial: 250 mg 1-3 times/day. Usual: 0.5-2 g. Max: 3 g/day.
Dose adjustment may be needed. Severe: Contraindicated.
Dose adjustment may be needed.
Should be taken with food.
Hypersensitivity to tolbutamide, sulfonylureas. Type 1 DM, diabetes w/ ketosis, acidosis, diabetic coma, or other acute complications (e.g. major surgery, severe infection or trauma), porphyria. Severe renal impairment.
Patient w/ G6PD deficiency, adrenocortical or thyroid function impairment. Hepatic and mild to moderate renal impairment. Elderly, debilitated and malnourished patients. Pregnancy and lactation.
Hypoglycaemia, nausea, epigastric fullness, heartburn, headache, pruritus, erythema, and urticarial, morbilliform or maculopapular eruptions, wt gain, hyponatraemia, syndrome of inappropriate secretion of antidiuretic hormone (SIADH), photosensitivity reactions. Rarely, hepatic dysfunction, jaundice, leucopenia, thrombocytopenia, pancytopenia, agranulocytosis, aplastic anaemia, and haemolytic anaemia.
Monitor blood glucose, glycosylated Hb level, signs and symptoms of hypoglycaemia.
Symptoms: Hypoglycaemia. Management: In conscious patient, admin glucose or 3-4 lumps of sugar w/ water. In comatose patient, admin up to 50 mL of 50% glucose soln via rapid IV inj followed by continuous infusion of a more dilute (10%) glucose soln.
Hypoglycaemic effect enhanced by protein-bound drugs (e.g. oral anticoagulants, hydantoins, salicylates, other NSAIDs, sulfonamides), chloramphenicol, MAOIs. Decreased hypoglycaemic effect w/ thiazides, other diuretics, phenothiazines, thyroid products, oestrogens, OC, phenytoin, nicotinic acid, corticosteroids, sympathomimetics, Ca channel blockers and isoniazid. Concomitant use w/ certain antifungals (e.g. miconazole, fluconazole) may increase plasma concentrations of tolbutamide.
Disulfiram-like reaction w/ alcohol.
May give false-positive result for urinary albumin w/ test using heat and acetic acid or sulfosalicylic acid. May interfere w/ test results of radioactive iodine uptake by decreasing uptake of radioactive iodine.
Description: Tolbutamide lowers blood glucose concentration principally by stimulating the secretion of endogenous insulin from pancreatic β-cells. It may enhance peripheral sensitivity to insulin and reduce basal hepatic glucose production during long-term admin. Onset: 1 hr. Duration: 6-24 hr. Pharmacokinetics: Absorption: Readily absorbed from the GI tract. Time to peak plasma concentration: W/in 3-5 hr. Distribution: Distributed into breast milk. Volume of distribution: 0.15 L/kg. Plasma protein binding: Approx 95%. Metabolism: Metabolised in the liver via hydroxylation mediated by CYP2C9 isoenzyme. Excretion: Via urine (75-85%) mainly as metabolites and faeces. Half-life: 4-7 hr.
Anon. Tolbutamide. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 19/08/2014.Buckingham R (ed). Tolbutamide. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 19/08/2014.McEvoy GK, Snow EK, Miller J et al (eds). Tolbutamide. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 19/08/2014.Tolbutamide Tablet (Mylan Pharmaceuticals Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 19/08/2014.