Glynase PresTab®

Name: Glynase PresTab®

Why is this medication prescribed?

Glyburide is used along with diet and exercise, and sometimes with other medications, to treat type 2 diabetes (condition in which the body does not use insulin normally and, therefore, cannot control the amount of sugar in the blood). Glyburide is in a class of medications called sulfonylureas. Glyburide lowers blood sugar by causing the pancreas to produce insulin (a natural substance that is needed to break down sugar in the body) and helping the body use insulin efficiently. This medication will only help lower blood sugar in people whose bodies produce insulin naturally. Glyburide is not used to treat type 1 diabetes (condition in which the body does not produce insulin and, therefore, cannot control the amount of sugar in the blood) or diabetic ketoacidosis (a serious condition that may occur if high blood sugar is not treated).

Over time, people who have diabetes and high blood sugar can develop serious or life-threatening complications, including heart disease, stroke, kidney problems, nerve damage, and eye problems. Taking medication(s), making lifestyle changes (e.g., diet, exercise, quitting smoking), and regularly checking your blood sugar may help to manage your diabetes and improve your health. This therapy may also decrease your chances of having a heart attack, stroke, or other diabetes-related complications such as kidney failure, nerve damage (numb, cold legs or feet; decreased sexual ability in men and women), eye problems, including changes or loss of vision, or gum disease. Your doctor and other healthcare providers will talk to you about the best way to manage your diabetes.

What should I do if I forget a dose?

Before you start to take glyburide, ask you doctor what you should do if you forget to take a dose. Write these directions down so that you can refer to them later.

As a general rule, take the missed dose as soon as you remember it. If it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What other information should I know?

Keep all appointments with your doctor and the laboratory. Your fasting blood sugar levels and glycosylated hemoglobin (HbA1c) should be checked regularly to determine your response to glyburide. Your doctor may order other lab tests to check your response to glyburide. Your doctor will also tell you how to check your response to this medication by measuring your blood sugar levels at home. Follow these instructions carefully.

You should always wear a diabetic identification bracelet to be sure you get proper treatment in an emergency.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

Description

GLYNASE PresTab 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 GLYNASE PresTab Tablets of 1.5 mg, 3 mg, and 6 mg strengths for oral administration. Inactive ingredients: colloidal silicon dioxide, corn starch, lactose, magnesium stearate. In addition, the 3 mg strength contains FD&C Blue No. 1 Aluminum Lake, and the 6 mg tablet contains D&C Yellow No. 10 Aluminum Lake. The chemical name for glyburide is 1-[[p-[2-(5-chloro-oanisamido)ethyl]phenyl]-sulfonyl]-3-cyclohexylurea and the molecular weight is 493.99. The structural formula is represented below:

Clinical pharmacology

Actions

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.

Some patients who are initially responsive to oral hypoglycemic drugs, including glyburide, may become unresponsive or poorly responsive over time. Alternatively, glyburide may be effective in some patients who have become unresponsive to one or more other sulfonylurea drugs.

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.

Pharmacokinetics

Single dose studies with GLYNASE PresTab Tablets in normal subjects demonstrate significant absorption of glyburide within one hour, peak drug levels at about two to three hours, and low but detectable levels at twenty-four hours.

Bioavailability studies have demonstrated that GLYNASE PresTab Tablets 3 mg provide serum glyburide concentrations that are not bioequivalent to those from MICRONASE® Tablets 5 mg. Therefore, the patient should be retitrated.

In a single-dose bioavailability study (see Figure A) in which subjects received GLYNASE PresTab Tablets 3 mg and MICRONASE Tablets 5 mg with breakfast, the peak of the mean serum glyburide concentration-time curve was 97.2 ng/mL for GLYNASE PresTab Tablets 3 mg and 87.5 ng/mL for MICRONASE Tablets 5 mg. The mean of the individual maximum serum concentration values of glyburide (Cmax) from GLYNASE PresTab Tablets 3 mg was 106 ng/mL and that from MICRONASE Tablets 5 mg was 104 ng/mL. The mean glyburide area under the serum concentration-time curve (AUC) for this study was 568 ng x hr/mL for GLYNASE PresTab Tablets 3 mg and 746 ng x hr/mL for MICRONASE Tablets 5 mg.

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 in diabetic patients demonstrate drug level concentration-time curves similar to single dose studies, indicating no buildup of drug in tissue depots.

In a steady-state study in diabetic patients receiving GLYNASE PresTab Tablets 6 mg once daily or GLYNASE PresTab Tablets 3 mg twice daily, no difference was seen between the two dosage regimens in average 24-hour glyburide concentrations following two weeks of dosing. The once-daily and twice-daily regimens provided equivalent glucose control as measured by fasting plasma glucose levels, 4-hour postprandial glucose AUC values, and 24-hour glucose AUC values. Insulin AUC response over the 24-hour period was not different for the two regimens. There were differences in insulin response between the regimens for the breakfast and supper 4-hour postprandial periods, but these did not translate into differences in glucose control.

The serum concentration of glyburide in normal subjects decreased with a half-life of about four hours.

In single dose studies in fasting normal subjects who were administered glyburide (MICRONASE Tablets) in doses ranging from 1.25 mg to 5 mg, 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 nonfasting 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 showed no reliable correlation between administered dose and serum drug level.

The major metabolite of glyburide is the 4-trans-hydroxy derivative. A second metabolite, the 3-cis-hydroxy derivative, also occurs. These metabolites probably 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. In vitro, 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 in clinical use.

Patient information

Patients should be informed of the potential risks and advantages of GLYNASE PresTab and of alternative modes of therapy. They also should be informed about the importance of adherence to dietary instructions, of a regular exercise program, and of regular testing of urine and/or blood glucose.

The risks of hypoglycemia, its symptoms and treatment, and conditions that predispose to its development should be explained to patients and responsible family members. Primary and secondary failure also should be explained.

Physician Counseling Information For Patients

In initiating treatment for type 2 diabetes, diet should be emphasized as the primary form of treatment. Caloric restriction and weight loss are essential in the obese diabetic patient. Proper dietary management alone may be effective in controlling the blood glucose and symptoms of hyperglycemia. The importance of regular physical activity should also be stressed, and cardiovascular risk factors should be identified and corrective measures taken where possible. Use of GLYNASE PresTab or other antidiabetic medications must be viewed by both the physician and patient as a treatment in addition to diet and not as a substitution or as a convenient mechanism for avoiding dietary restraint. Furthermore, loss of blood glucose control on diet alone may be transient, thus requiring only short-term administration of GLYNASE PresTab or other antidiabetic medications. Maintenance or discontinuation of GLYNASE PresTabs or other antidiabetic medications should be based on clinical judgment using regular clinical and laboratory evaluations.

Laboratory Tests

Therapeutic response to GLYNASE PresTab Tablets should be monitored by frequent urine glucose tests and periodic blood glucose tests. Measurement of glycosylated hemoglobin levels may be helpful in some patients.

What happens if i miss a dose (diabeta, glynase prestab, micronase)?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

Where can i get more information?

Your pharmacist can provide more information about glyburide.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

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Side effects

Hypoglycemia

See PRECAUTIONS and OVERDOSAGE Sections.

Gastrointestinal Reactions

Cholestatic jaundice and hepatitis may occur rarely which may progress to liver failure; GLYNASE PresTab Tablets should be discontinued if this occurs.

Liver function abnormalities, including isolated transaminase elevations, have been reported.

Gastrointestinal disturbances, eg, nausea, epigastric fullness, and heartburn are the most common reactions, having occurred in 1.8% of treated patients during clinical trials. They tend to be dose related and may disappear when dosage is reduced.

Dermatologic Reactions

Allergic skin reactions, eg, pruritus, erythema, urticaria, and morbilliform or maculopapular eruptions occurred in 1.5% of treated patients during clinical trials. These may be transient and may disappear despite continued use of glyburide. If skin reactions persist, the drug should be discontinued.

Porphyria cutanea tarda and photosensitivity reactions have been reported with sulfonylureas.

Hematologic Reactions

Leukopenia, agranulocytosis, thrombocytopenia, hemolytic anemia (see PRECAUTIONS), aplastic anemia, and pancytopenia have been reported with sulfonylureas.

Metabolic Reactions

Hepatic porphyria and disulfiram-like reactions have been reported with sulfonylureas; however, hepatic porphyria has not been reported with glyburide and disulfiram-like reactions have been reported very rarely.

Cases of hyponatremia have been reported with glyburide and all other sulfonylureas, most often in patients who are on other medications or have medical conditions known to cause hyponatremia or increase release of antidiuretic hormone. The syndrome of inappropriate antidiuretic hormone (SIADH) secretion has been reported with certain other sulfonylureas, and it has been suggested that these sulfonylureas may augment the peripheral (antidiuretic) action of ADH and/or increase release of ADH.

Other Reactions

Changes in accommodation and/or blurred vision have been reported with glyburide and other sulfonylureas. These are thought to be related to fluctuation in glucose levels.

In addition to dermatologic reactions, allergic reactions such as angioedema, arthralgia, myalgia and vasculitis have been reported.

Read the entire FDA prescribing information for Glynase Prestab (Micronized Glyburide Tablets)

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