Pharmaceutics

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GLIPIZIDE EXTENDED RELEASE TABLETS
FOR ORAL USE
DESCRIPTION Glipizide is an oral blood-glucose-lowering drug of the sulfonylurea class. The Chemical Abstracts name of glipizide is 1-cyclohexyl-3-[[p-[2-(5methylpyrazinecarboxamido)ethyl] phenyl]sulfonyl]urea. The molecular formula is C21H27N5O4S; the molecular weight is 445.55; the structural formula is shown below: N HC

3

N

CONHCH2CH2

SO NHCONH 2

Glipizide is a whitish, odorless powder with a pKa of 5.9. It is insoluble in water and alcohols, but soluble in 0.1 N NaOH; it is freely soluble in dimethylformamide. Glipizide extendedrelease tablets are formulated as a once-a-day controlled release tablet for oral use and is designed to deliver 2.5, 5, or 10 mg of glipizide. Inert ingredients in the 2.5 mg, 5 mg and 10 mg formulations are: polyethylene oxide, hypromellose, magnesium stearate, sodium chloride, red ferric oxide, cellulose acetate, polyethylene glycol, Opadry® blue (OY-LS-20921)(2.5 mg tablets), Opadry® white (YS-2-7063)(5 mg and 10 mg tablet) and black ink (S-1-8106). System Components and Performance Glipizide extended-release tablets are similar in appearance to a conventional tablet. It consists, however, of an osmotically active drug core surrounded by a semipermeable membrane. The core itself is divided into two layers: an “active” layer containing the drug, and a “push” layer containing pharmacologically inert (but osmotically active) components. The membrane surrounding the tablet is permeable to water but not to drug or osmotic excipients. As water from the gastrointestinal tract enters the tablet, pressure increases in the osmotic layer and “pushes” against the drug layer, resulting in the release of drug through a small, laser-drilled orifice in the membrane on the drug side of the tablet. Glipizide extended-release tablets are designed to provide a controlled rate of delivery of glipizide into the gastrointestinal lumen which is independent of pH or gastrointestinal motility. The function of the glipizide extended-release tablets depends upon the existence of an osmotic 1

gradient between the contents of the bi-layer core and fluid in the GI tract. Drug delivery is essentially constant as long as the osmotic gradient remains constant, and then gradually falls to zero. The biologically inert components of the tablet remain intact during GI transit and are eliminated in the feces as an insoluble shell. CLINICAL PHARMACOLOGY Mechanism of Action: Glipizide appears to lower blood glucose acutely by stimulating the release of insulin from the pancreas, an effect dependent upon functioning beta cells in the pancreatic islets. Extrapancreatic effects also may play a part in the mechanism of action of oral sulfonylurea hypoglycemic drugs. Two extrapancreatic effects shown to be important in the action of glipizide are an increase in insulin sensitivity and a decrease in hepatic glucose production. However, the mechanism by which glipizide lowers blood glucose during long-term administration has not been clearly established. Stimulation of insulin secretion by glipizide in response to a meal is of major importance. The insulinotropic response to a meal is enhanced with glipizide extended-release tablet administration in diabetic patients. The postprandial insulin and C-peptide responses continue to be enhanced after at least 6 months of treatment. In 2 randomized, double-blind, dose-response studies comprising a total of 347 patients, there was no significant increase in fasting insulin in all glipizide extended-release tablet-treated patients combined compared to placebo, although minor elevations were observed at some doses. There was no increase in fasting insulin over the long term. Some patients fail to respond initially, or gradually lose their responsiveness to sulfonylurea drugs, including glipizide. Alternatively, glipizide may be effective in some patients who have not responded or have ceased to respond to other sulfonylureas....
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