Glipizide (Page 3 of 5)

8.4 Pediatric Use

Safety and effectiveness in children have not been established.

8.5 Geriatric Use

There were no overall differences in effectiveness or safety between younger and older patients, but greater sensitivity of some individuals cannot be ruled out. Elderly patients are particularly susceptible to the hypoglycemic action of anti-diabetic agents. Hypoglycemia may be difficult to recognize in these patients. Therefore, dosing should be conservative to avoid hypoglycemia [see Dosage and Administration (2.1), Warnings and Precautions (5.1) and Clinical Pharmacology (12.3)].

8.6 Hepatic Impairment

There is no information regarding the effects of hepatic impairment on the disposition of glipizide. However, since glipizide is highly protein bound and hepatic biotransformation is the predominant route of elimination, the pharmacokinetics and/or pharmacodynamics of glipizide may be altered in patients with hepatic impairment. If hypoglycemia occurs in such patients, it may be prolonged and appropriate management should be instituted [see Dosage and Administration (2.1), Warnings and Precautions (5.1) and Clinical Pharmacology (12.3)].

10 OVERDOSAGE

Overdosage of sulfonylureas including glipizide extended-release tablets can produce severe hypoglycemia. Mild hypoglycemic symptoms without loss of consciousness or neurologic findings should be treated with oral glucose. Severe hypoglycemic reactions with coma, seizure, or other neurological impairment are medical emergencies requiring immediate treatment. The patient should be treated with glucagon or intravenous glucose. Patients should be closely monitored for a minimum of 24 to 48 hours since hypoglycemia may recur after apparent clinical recovery. Clearance of glipizide from plasma may be prolonged in persons with liver disease. Because of the extensive protein binding of glipizide, dialysis is unlikely to be of benefit.

11 DESCRIPTION

Glipizide extended-release tablets (glipizide) is an oral sulfonylurea.

The Chemical Abstracts name of glipizide is 1-cyclohexyl-3-[[p-[2-(5-methylpyrazinecarboxamido)ethyl] phenyl]sulfonyl]urea. The molecular formula is C21 H27 N5 O4 S; the molecular weight is 445.55; the structural formula is shown below:

Chemical Structure
(click image for full-size original)

Glipizide is a white or almost white crystalline 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.
Inert ingredients in the 2.5 mg, 5 mg and 10 mg formulations are: acetyltributyl citrate, ammonium hydroxide, hydroxyethyl cellulose, hydroxypropyl cellulose, iron oxide black, lactose monohydrate, magnesium stearate, methacrylic acid and methyl methacrylate copolymer (1:1), polyethylene glycol, propylene glycol and shellac glaze in ethanol.

System Components and Performance

Glipizide extended-release tablets are formulated as a polymer matrix based once-a-day controlled release tablet for oral use and is designed to deliver 2.5 mg, 5 mg or 10 mg of glipizide.

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Glipizide primarily lowers blood glucose by stimulating the release of insulin from the pancreas, an effect dependent upon functioning beta cells in the pancreatic islets. Sulfonylureas bind to the sulfonylurea receptor in the pancreatic beta-cell plasma membrane, leading to closure of the ATP-sensitive potassium channel, thereby stimulating the release of insulin.

12.2 Pharmacodynamics

The insulinotropic response to a meal is enhanced with glipizide extended-release tablets administration in diabetic patients. The postprandial insulin and C-peptide responses continue to be enhanced after at least 6 months of treatment. In two 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 tablets-treated patients combined compared to placebo, although minor elevations were observed at some doses.
In studies of glipizide extended-release tablets in subjects with type 2 diabete mellitus, once daily administration produced reductions in hemoglobin A1c, fasting plasma glucose and postprandial glucose. The relationship between dose and reduction in hemoglobin A1c was not established, however subjects treated with 20 mg had a greater reduction in fasting plasma glucose compared to subjects treated with 5 mg.

12.3 Pharmacokinetics

Absorption

The absolute bioavailability of glipizide was 100% after single oral doses in patients with type 2 diabetes mellitus. Beginning 2 to 3 hours after administration of glipizide extended-release tablets, plasma drug concentrations gradually rise reaching maximum concentrations within 6 to 12 hours after dosing. With subsequent once daily dosing of glipizide extended-release tablets, plasma glipizide concentrations are maintained throughout the 24 hour dosing interval with less peak to trough fluctuation than that observed with twice daily dosing of immediate release glipizide.
The mean relative bioavailability of glipizide in 21 males with type 2 diabetes mellitus after administration of 20 mg glipizide extended-release tablets, compared to immediate release glipizide (10 mg given twice daily), was 90% at steady-state. Steady-state plasma concentrations were achieved by at least the fifth day of dosing with glipizide extended-release tablets in 21 males with type 2 diabetes mellitus and patients younger than 65 years. No accumulation of drug was observed in patients with type 2 diabetes mellitus during chronic dosing with glipizide extended-release tablets.
Administration of glipizide extended-release tablets with food has no effect on the 2 to 3 hour lag time in drug absorption. In a single dose, food effect study in 21 healthy male subjects, the administration of glipizide extended-release tablets immediately before a high fat breakfast resulted in a 40% increase in the glipizide mean Cmax value, which was significant, but the effect on the AUC was not significant. There was no change in glucose response between the fed and fasting state. Markedly reduced GI retention times of the glipizide extended-release tablets over prolonged periods (e.g., short bowel syndrome) may influence the pharmacokinetic profile of the drug and potentially result in lower plasma concentrations.
In a multiple dose study in 26 males with type 2 diabetes mellitus, the pharmacokinetics of glipizide were linear with glipizide extended-release tablets in that the plasma drug concentrations increased proportionately with dose. In a single dose study in 24 healthy subjects, four 5 mg, two 10 mg, and one 20 mg glipizide extended-release tablets were bioequivalent. In a separate single dose study in 36 healthy subjects, four 2.5 mg glipizide extended-release tablets were bioequivalent to one 10 mg glipizide extended-release tablet.
Distribution
The mean volume of distribution was approximately 10 liters after single intravenous doses in patients with type 2 diabetes mellitus. Glipizide is 98 to 99% bound to serum proteins, primarily to albumin.
Metabolism
The major metabolites of glipizide are products of aromatic hydroxylation and have no hypoglycemic activity. A minor metabolite, an acetylamino-ethyl benzene derivative, which accounts for less than 2% of a dose, is reported to have 1/10 to 1/3 as much hypoglycemic activity as the parent compound.
Elimination
Glipizide is eliminated primarily by hepatic biotransformation: less than 10% of a dose is excreted as unchanged drug in urine and feces; approximately 90% of a dose is excreted as biotransformation products in urine (80%) and feces (10%).
The mean total body clearance of glipizide was approximately 3 liters per hour after single intravenous doses in patients with type 2 diabetes mellitus. The mean terminal elimination half-life of glipizide ranged from 2 to 5 hours after single or multiple doses in patients with type 2 diabetes mellitus.
Specific Populations

Pediatric:
Studies characterizing the pharmacokinetics of glipizide in pediatric patients have not been performed.
Geriatric:
There were no differences in the pharmacokinetics of glipizide after single dose administration to older diabetic subjects compared to younger healthy subjects [see Use in Specific Populations (8.5)].

Renal Impairment:
The pharmacokinetics of glipizide has not been evaluated in patients with varying degree of renal impairment. Limited data indicates that glipizide biotransformation products may remain in circulation for a longer time in subjects with renal impairment than that seen in subjects with normal renal function.
Hepatic Impairment:
The pharmacokinetics of glipizide has not been evaluated in patients with hepatic impairment.
Drug-drug Interactions

Miconazole
A potential interaction between oral miconazole and oral glipizide leading to severe hypoglycemia has been reported. Whether this interaction also occurs with the intravenous, topical, or vaginal preparations of miconazole is not known [see Drug Interactions (7.2)].

Fluconazole
Concomitant treatment with fluconazole increases plasma concentrations of glipizide. The effect of concomitant administration of Diflucan® (fluconazole) and glipizide has been demonstrated in a placebo controlled crossover study in healthy volunteers. All subjects received glipizide alone and following treatment with 100 mg of Diflucan® as a single daily oral dose for 7 days. The mean percentage increase in the glipizide AUC after fluconazole administration was 56.9% (range: 35 to 81%) [see Drug Interactions (7.3)].
Colesevelam
Colesevelam can reduce the maximum plasma concentration and total exposure of glipizide when the two are coadministered. In studies assessing the effect of colesevelam on the pharmacokinetics of glipizide ER in healthy volunteers, reductions in glipizide AUC0-∞ and Cmax of 12% and 13%, respectively were observed when colesevelam was coadministered with glipizide ER. When glipizide ER was administered 4 hours prior to colesevelam, there was no significant change in glipizide AUC0-∞ or Cmax , -4% and 0%, respectively [see Drug Interactions (7.4)].

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