indication

For treatment of NIDDM (non-insulin-dependent diabetes mellitus) in conjunction with diet and exercise.

pharmacology

Tolbutamide, a first-generation sulfonylurea antidiabetic agent, is used with diet to lower blood glucose levels in patients with diabetes mellitus type II. Tolbutamide is twice as potent as the related second-generation agent glipizide. Tolbutamide lowers blood sugar by stimulating the pancreas to secrete insulin and helping the body use insulin efficiently. The pancreas must be able to produce insulin for this drug to work.

mechanism of action

Sulfonylureas lower blood glucose in patients with NIDDM by directly stimulating the acute release of insulin from functioning beta cells of pancreatic islet tissue by an unknown process that involves a sulfonylurea receptor (receptor 1) on the beta cell. Sulfonylureas inhibit the ATP-potassium channels on the beta cell membrane and potassium efflux, which results in depolarization and calcium influx, calcium-calmodulin binding, kinase activation, and release of insulin-containing granules by exocytosis, an effect similar to that of glucose.

toxicity

Oral, mouse: LD₅₀ = 2600 mg/kg

biotransformation

Metabolized in the liver principally via oxidation of the p-methyl group producing the carboxyl metabolite, 1-butyl-3-p-carboxyphenylsulfonylurea. May also be metabolized to hydroxytolbutamide. Tolbutamide does not undergo acetylation like antibacterial sulfonamides as it does not have a p-amino group.

absorption

Readily absorbed following oral administration. Tolbutamide is detectable in plasma 30-60 minutes following oral administration of a single dose with peak plasma concentrations occurring within 3-5 hours. Absorption is unaltered if taken with food but is increased with high pH.

half life

Approximately 7 hours with interindividual variations ranging from 4-25 hours. Tolbutamide has the shortest duration of action, 6-12 hours, of the antidiabetic sulfonylureas.

route of elimination

Unchanged drug and metabolites are eliminated in the urine and feces. Approximately 75-85% of a single orally administered dose is excreted in the urine principally as the 1-butyl-3-p-carboxyphenylsulfonylurea within 24 hours.

drug interactions

Acebutolol: Acebutolol may decrease symptoms of hypoglycemia and increase the time required for the body to compensate for hypoglycemia.

Acenocoumarol: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Acenocoumarol. Consider alternate therapy or monitor for changes in Acenocoumarol therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Acetylsalicylic acid: Acetylsalicylic acid increases the effect of the sulfonylurea, tolbutamide.

Atenolol: The beta-blocker, atenolol, may decrease symptoms of hypoglycemia.

Bisoprolol: The beta-blocker, bisoprolol, may decrease symptoms of hypoglycemia.

Bosentan: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Bosentan. Consider alternate therapy or monitor for changes in Bosentan therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Capecitabine: Capecitabine, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Capecitabine is initiated, discontinued or dose changed.

Carvedilol: The beta-blocker, carvedilol, may decrease symptoms of hypoglycemia.

Celecoxib: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Celecoxib. Consider alternate therapy or monitor for changes in Celecobix therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Chloramphenicol: Chloramphenicol may increase the effect of sulfonylurea, tolbutamide.

Clofibrate: Clofibrate may increase the effect of sulfonylurea, tolbutamide.

Dapsone: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Dapsone. Consider alternate therapy or monitor for changes in Dapsone therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Delavirdine: Delavirdine, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Delavirdine is initiated, discontinued or dose changed.

Digoxin: Tolbutamide increases the effect of digoxin

Esmolol: The beta-blocker, esmolol, may decrease symptoms of hypoglycemia.

Floxuridine: Floxuridine, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Floxuridine is initiated, discontinued or dose changed.

Fluconazole: Fluconazole, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Fluconazole therapeutic and adverse effects if Delavirdine is initiated, discontinued or dose changed.

Fluorouracil: Fluorouracil, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Fluorouracil is initiated, discontinued or dose changed.

Fluoxetine: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Fluoxetine. Consider alternate therapy or monitor for changes in Fluoxetine therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Flurbiprofen: Flurbiprofen, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Flurbiprofen is initiated, discontinued or dose changed.

Fosphenytoin: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Fosphenytoin. Consider alternate therapy or monitor for changes in Fosphenytoin therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Gemfibrozil: Gemfibrozil, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Gemfibrozil is initiated, discontinued or dose changed.

Glimepiride: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Glimepiride. Consider alternate therapy or monitor for changes in Glimepiride therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Glipizide: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Glipizide. Consider alternate therapy or monitor for changes in Glipizide therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Ibuprofen: Ibuprofen, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Ibuprofen is initiated, discontinued or dose changed.

Indomethacin: Indomethacin, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Indomethacin is initiated, discontinued or dose changed.

Ketamine: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Ketamine. Consider alternate therapy or monitor for changes in Ketamine therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Ketoconazole: Ketoconazole, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Ketoconazole is initiated, discontinued or dose changed.

Labetalol: The beta-blocker, labetalol, may decrease symptoms of hypoglycemia.

Losartan: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Losartan. Consider alternate therapy or monitor for changes in Losartan therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Lumiracoxib: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Lumiracoxib. Consider alternate therapy or monitor for changes in Lumiracoxib therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Mefenamic acid: Mefanamic acid, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Mefanamic acid is initiated, discontinued or dose changed.

Mestranol: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Mestranol. Consider alternate therapy or monitor for changes in Mestranol therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Metoprolol: The beta-blocker, metoprolol, may decrease symptoms of hypoglycemia.

Miconazole: Miconazole, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Miconazole is initiated, discontinued or dose changed.

Montelukast: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Montelukast. Consider alternate therapy or monitor for changes in Montelukast therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Nadolol: The beta-blocker, nadolol, may decrease symptoms of hypoglycemia.

Nateglinide: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Nateglinide. Consider alternate therapy or monitor for changes in Nateglinide therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Nicardipine: Nicardipine, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Nicardipine is initiated, discontinued or dose changed.

Oxprenolol: The beta-blocker, oxprenolol, may decrease symptoms of hypoglycemia.

Paclitaxel: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Paclitaxel. Consider alternate therapy or monitor for changes in Paclitaxel therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Phenylbutazone: Phenylbutazone increases the effect of the hypoglycemic agent

Phenytoin: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Phenytoin. Consider alternate therapy or monitor for changes in Phenytoin therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Pindolol: The beta-blocker, pindolol, may decrease symptoms of hypoglycemia.

Piroxicam: Piroxicam, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Piroxicam is initiated, discontinued or dose changed.

Propranolol: The beta-blocker, propranolol, may decrease symptoms of hypoglycemia.

Rifampin: Rifampin may decrease the effect of sulfonylurea, tolbutamide.

Sitaxentan: Sitaxsentan, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Sitaxsentan is initiated, discontinued or dose changed.

Somatropin recombinant: Somatropin may antagonize the hypoglycemic effect of Tolbutamide. Dose adjustments of Tolbutamide may be required.

Sulfadiazine: Tolbutamide and Sulfadiazine are strong CYP2C9 inhibitors and substrates. Decreased metabolism and clearance of both agents may occur during concomitant therapy. Consider alternate therpy or monitor for changes in the therapeutic and adverse effects of both agents if concomitant therapy is initiated, discontinued or dose(s) changed.

Sulfamethoxazole: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Sulfamethoxazole. Consider alternate therapy or monitor for changes in Sulfamethoxazole therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Sulfinpyrazone: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Sulfinpyrazone. Consider alternate therapy or monitor for changes in Sulfinpyrazone therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Sulfisoxazole: Tolbutamide and Sulfisoxazole are strong CYP2C9 inhibitors and substrates. Decreased metabolism and clearance of both agents may occur during concomitant therapy. Consider alternate therpy or monitor for changes in the therapeutic and adverse effects of both agents if concomitant therapy is initiated, discontinued or dose(s) changed.

Tamoxifen: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tamoxifen. Consider alternate therapy or monitor for changes in Tamoxifen therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Timolol: The beta-blocker, timolol, may decrease symptoms of hypoglycemia.

Torasemide: Tolbutamide, a strong CYP2C9 inhibitor, may increase the serum concentration of Torasemide, a CYP2C9 substrate, by decreasing its metabolism and clearance. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of Torasemide if Tolbutamide is initiated, discontinued or dose changed.

Trimethoprim: The strong CYP2C9 inhibitor, Tolbutamide, may decrease the metabolism and clearance of Trimethoprim, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in therapeutic and adverse effects of Trimethoprim if Tolbutamide is initiated, discontinued or dose changed.

Voriconazole: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Voriconazole. Consider alternate therapy or monitor for changes in Voriconazole therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.

Warfarin: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism of warfarin. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of warfarin if tolbutamide is initiated, discontinued or dose changed.

Zafirlukast: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of zafirlukast. Consider alternate therapy or monitor for changes in zafirlukast therapeutic and adverse effects if tolbutamide is initiated, discontinued or dose changed.

Zopiclone: Tolbutamide, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Zopiclone. Consider alternate therapy or monitor for changes in Zopiclone therapeutic and adverse effects if Tolbutamide is initiated, discontinued or dose changed.