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Glyburide (Glyburide) - Description and Clinical Pharmacology

 
 



DESCRIPTION

Glyburide tablets contain micronized (smaller particle size) glyburide, which is an oral blood-glucose-lowering drug of the sulfonylurea class. Glyburide is a white, crystalline compound, formulated as glyburide tablets of 1.25, 2.5, and 5 mg strengths for oral administration.

Inactive ingredients: lactose monohydrate, microcrystalline cellulose, magnesium stearate. In addition, the contains FD&C Red No.40 and the contains FD&C Blue No.1. The chemical name for glyburide is 1-[[p-[2-(5-chloro-o-anisamido)-ethyl] phenyl]-sulfonyl]-3-cyclohexylurea and the molecular weight is 493.99. The structural formula is represented below. 2.5 mg 5 mg

CLINICAL PHARMACOLOGY

Glyburide appears to lower the blood glucose acutely by stimulating the release of insulin from the pancreas, an effect dependent upon functioning beta cells in the pancreatic islets. The mechanism by which glyburide lowers blood glucose during long-term administration has not been clearly established.With chronic administration in Type II diabetic patients, the blood glucose lowering effect persists despite a gradual decline in the insulin secretory response to the drug. Extrapancreatic effects may be involved in the mechanism of action of oral sulfonylurea hypoglycemic drugs. The combination of glyburide and metformin may have a synergistic effect, since both agents act to improve glucose tolerance by different but complementary mechanisms.

In addition to its blood glucose lowering actions, glyburide produces a mild diuresis by enhancement of renal free water clearance.

Disulfiram-like reactions have very rarely been reported in patients treated with glyburide tablets.

Pharmacokinetics

Single dose studies with glyburide tablets in normal subjects demonstrate significant absorption within one hour, peak drug levels at about four hours, and low but detectable levels at twenty-four hours. Mean serum levels of glyburide, as reflected by areas under the serum concentration-time curve, increase in proportion to corresponding increases in dose. Multiple dose studies with glyburide tablets in diabetic patients demonstrate drug level concentration-time curves similar to single dose studies, indicating no buildup of drug in tissue depots. The decrease of glyburide in the serum of normal healthy individuals is biphasic; the terminal half-life is about 10 hours. In single dose studies in fasting normal subjects, the degree and duration of blood glucose lowering is proportional to the dose administered and to the area under the drug level concentration-time curve. The blood glucose lowering effect persists for 24 hours following single morning doses in non-fasting diabetic patients. Under conditions of repeated administration in diabetic patients, however, there is no reliable correlation between blood drug levels and fasting blood glucose levels. A one year study of diabetic patients treated with glyburide tablets showed no reliable correlation between administered dose and serum drug level.

The major metabolite of glyburide is the 4-transhydroxy derivative. A second metabolite, the 3-cishydroxy derivative, also occurs. These metabolites contribute no significant hypoglycemic action in humans since they are only weakly active (1/400th and 1/40th as active, respectively, as glyburide) in rabbits.

Glyburide is excreted as metabolites in the bile and urine, approximately 50% by each route. This dual excretory pathway is qualitatively different from that of other sulfonylureas, which are excreted primarily in the urine.

Sulfonylurea drugs are extensively bound to serum proteins. Displacement from protein binding sites by other drugs may lead to enhanced hypoglycemic action., the protein binding exhibited by glyburide is predominantly non-ionic, whereas that of other sulfonylureas (chlorpropamide, tolbutamide, tolazamide) is predominantly ionic. Acidic drugs such as phenylbutazone, warfarin, and salicylates displace the ionic-binding sulfonylureas from serum proteins to a far greater extent than the non-ionic binding glyburide. It has not been shown that this difference in protein binding will result in fewer drug-drug interactions with glyburide tablets in clinical use. In vitro

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