Glyburide and Metformin Hydrochloride

GLYBURIDE AND METFORMIN HYDROCHLORIDE- glyburide and metformin hydrochloride tablet
Cadila Healthcare Limited

DESCRIPTION

Glyburide and Metformin Hydrochloride Tablets, USP contain 2 oral antihyperglycemic drugs used in the management of type 2 diabetes, glyburide, USP and metformin hydrochloride, USP.

Glyburide, USP is an oral antihyperglycemic drug of the sulfonylurea class. The chemical name for glyburide is 1-[[p -[2-(5-chloro-o -anisamido)ethyl]phenyl]sulfonyl]-3-cyclo-hexylurea. Glyburide, USP is a white or almost white, crystalline powder with a molecular formula of C23 H28 ClN3 O5 S and a molecular weight of 494. The glyburide used in glyburide and metformin hydrochloride tablets, USP has a particle size at least 20% are less than 2 micron, at least 80% are less than 10 micron and 100% are less than 40 micron. The structural formula is represented below.

figure

Metformin hydrochloride, USP is an oral antihyperglycemic drug used in the management of type 2 diabetes. Metformin hydrochloride (N ,N -dimethylimidodicarbonimidic diamide monohydrochloride) is not chemically or pharmacologically related to sulfonylureas, thiazolidinediones, or α-glucosidase inhibitors. It is a white crystals with a molecular formula of C4 H12 ClN5 (monohydrochloride) and a molecular weight of 165.62. Metformin hydrochloride, USP is freely soluble in water, slightly soluble in ethanol (95%), practically insoluble in acetone and in methylene chloride. The structural formula is as shown:

figure

Each glyburide and metformin hydrochloride tablet, USP intended for oral administration contains 1.25 mg glyburide USP with 250 mg metformin hydrochloride USP, 2.5 mg glyburide USP with 500 mg metformin hydrochloride USP and 5 mg glyburide USP with 500 mg metformin hydrochloride USP. In addition, each tablet contains the following inactive ingredients: calcium carbonate, croscarmellose sodium, magnesium stearate, microcrystalline cellulose and povidone.

Additionally, 1.25 mg/250 mg tablets contain opadry II white 33F28398 which contains hypromellose, lactose monohydrate, polyethylene glycol, talc and titanium dioxide.

Additionally, 2.5 mg/500 mg tablets contain opadry II orange 31F530003 which contains FD&C blue #2 aluminum lake, FD&C yellow #5 aluminum lake, FD&C yellow #6 aluminum lake, hypromellose, lactose monohydrate, polyethylene glycol and titanium dioxide.

Additionally, 5 mg/500 mg tablets contain opadry II green 31F510000 which contains iron oxide black, iron oxide red, iron oxide yellow, hypromellose, lactose monohydrate, polyethylene glycol and titanium dioxide.

CLINICAL PHARMACOLOGY

Mechanism of Action

Glyburide and metformin hydrochloride tablet combines glyburide and metformin hydrochloride, 2 antihyperglycemic agents with complementary mechanisms of action, to improve glycemic control in patients with type 2 diabetes.

Glyburide 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. The mechanism by which glyburide lowers blood glucose during long-term administration has not been clearly established. With chronic administration in patients with type 2 diabetes, 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.

Metformin hydrochloride is an antihyperglycemic agent that improves glucose tolerance in patients with type 2 diabetes, lowering both basal and postprandial plasma glucose. Metformin hydrochloride decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization.

Pharmacokinetics

Absorption and Bioavailability

Glyburide and Metformin Hydrochloride

In bioavailability studies of glyburide and metformin hydrochloride 2.5 mg/500 mg and 5 mg/500 mg, the mean area under the plasma concentration versus time curve (AUC) for the glyburide component was 18% and 7%, respectively, greater than that of the Micronase® brand of glyburide coadministered with metformin. The glyburide component of glyburide and metformin hydrochloride, therefore, is not bioequivalent to Micronase®. The metformin component of glyburide and metformin hydrochloride is bioequivalent to metformin coadministered with glyburide.

Following administration of a single glyburide and metformin hydrochloride 5 mg/500 mg tablet with either a 20% glucose solution or a 20% glucose solution with food, there was no effect of food on the Cmax and a relatively small effect of food on the AUC of the glyburide component. The Tmax for the glyburide component was shortened from 7.5 hours to 2.75 hours with food compared to the same tablet strength administered fasting with a 20% glucose solution. The clinical significance of an earlier Tmax for glyburide after food is not known. The effect of food on the pharmacokinetics of the metformin component was indeterminate.

Glyburide

Single-dose studies with Micronase® tablets in normal subjects demonstrate significant absorption of glyburide within 1 hour, peak drug levels at about 4 hours, and low but detectable levels at 24 hours. Mean serum levels of glyburide, as reflected by areas under the serum concentration-time curve, increase in proportion to corresponding increases in dose. Bioequivalence has not been established between glyburide and metformin hydrochloride and single-ingredient glyburide products.

Metformin Hydrochloride

The absolute bioavailability of a 500 mg metformin hydrochloride tablet given under fasting conditions is approximately 50% to 60%. Studies using single oral doses of metformin tablets of 500 mg and 1500 mg, and 850 mg to 2550 mg, indicate that there is a lack of dose proportionality with increasing doses, which is due to decreased absorption rather than an alteration in elimination.

Food decreases the extent of and slightly delays the absorption of metformin, as shown by approximately a 40% lower peak concentration and a 25% lower AUC in plasma and a 35-minute prolongation of time to peak plasma concentration following administration of a single 850 mg tablet of metformin with food, compared to the same tablet strength administered fasting. The clinical relevance of these decreases is unknown.

Distribution

Glyburide

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 results in fewer drug-drug interactions with glyburide tablets in clinical use.

Metformin Hydrochloride

The apparent volume of distribution (V/F) of metformin following single oral doses of 850 mg averaged 654±358 L. Metformin is negligibly bound to plasma proteins. Metformin partitions into erythrocytes, most likely as a function of time. At usual clinical doses and dosing schedules of metformin, steady state plasma concentrations of metformin are reached within 24 to 48 hours and are generally <1 mcg/mL. During controlled clinical trials, maximum metformin plasma levels did not exceed 5 mcg/mL, even at maximum doses.

Metabolism and Elimination

Glyburide

The decrease of glyburide in the serum of normal healthy individuals is biphasic; the terminal half-life is about 10 hours. 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 (1/400 and 1/40 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.

Metformin Hydrochloride

Intravenous single-dose studies in normal subjects demonstrate that metformin is excreted unchanged in the urine and does not undergo hepatic metabolism (no metabolites have been identified in humans) nor biliary excretion. Renal clearance (see Table 1) is approximately 3.5 times greater than creatinine clearance, which indicates that tubular secretion is the major route of metformin elimination. Following oral administration, approximately 90% of the absorbed drug is eliminated via the renal route within the first 24 hours, with a plasma elimination half-life of approximately 6.2 hours. In blood, the elimination half-life is approximately 17.6 hours, suggesting that the erythrocyte mass may be a compartment of distribution.

Special Populations

Patients With Type 2 Diabetes

Multiple-dose studies with glyburide in patients with type 2 diabetes demonstrate drug level concentration-time curves similar to single-dose studies, indicating no buildup of drug in tissue depots.

In the presence of normal renal function, there are no differences between single- or multiple-dose pharmacokinetics of metformin between patients with type 2 diabetes and normal subjects (see Table 1), nor is there any accumulation of metformin in either group at usual clinical doses.

Hepatic Insufficiency

No pharmacokinetic studies have been conducted in patients with hepatic insufficiency for either glyburide or metformin.

Renal Insufficiency

No information is available on the pharmacokinetics of glyburide in patients with renal insufficiency.

In patients with decreased renal function (based on creatinine clearance), the plasma and blood half-life of metformin is prolonged and the renal clearance is decreased in proportion to the decrease in creatinine clearance (see Table 1; also, see WARNINGS).

Geriatrics

There is no information on the pharmacokinetics of glyburide in elderly patients.

Limited data from controlled pharmacokinetic studies of metformin in healthy elderly subjects suggest that total plasma clearance is decreased, the half-life is prolonged, and Cmax is increased, when compared to healthy young subjects. From these data, it appears that the change in metformin pharmacokinetics with aging is primarily accounted for by a change in renal function (see Table 1). Metformin treatment should not be initiated in patients ≥80 years of age unless measurement of creatinine clearance demonstrates that renal function is not reduced.

Table 1: Select Mean (±SD) Metformin Pharmacokinetic Parameters Following Single or Multiple Oral Doses of Metformin
*
All doses given fasting except the first 18 doses of the multiple-dose studies
Peak plasma concentration
Time to peak plasma concentration
§
SD=single dose
Combined results (average means) of 5 studies: mean age 32 years (range 23 to 59 years)
#
Kinetic study done following dose 19, given fasting
Þ
Elderly subjects, mean age 71 years (range 65 to 81 years)
ß
CLc r =creatinine clearance normalized to body surface area of 1.73 m2
Subject Groups : Metformin Dose * ( number of subjects ) Cm a x ( mcg / mL ) Tm a x ( hrs ) Renal Clearance ( mL / min )
Healthy , nondiabetic adults :
500 mg SD § (24) 1.03 (±0.33) 2.75 (±0.81) 600 (±132)
850 mg SD (74) 1.60 (±0.38) 2.64 (±0.82) 552 (±139)
850 mg t.i.d. for 19 doses # (9) 2.01 (±0.42) 1.79 (±0.94) 642 (±173)
Adults with type 2 diabetes :
850 mg SD (23) 1.48 (±0.5) 3.32 (±1.08) 491 (±138)
850 mg t.i.d. for 19 doses # (9) 1.90 (±0.62) 2.01 (±1.22) 550 (±160)
Elderly Þ, healthy nondiabetic adults :
850 mg SD (12) 2.45 (±0.70) 2.71 (±1.05) 412 (±98)
Renal - impaired adults : 850 mg SD
Mild (CLc r ß 61 to 90 mL/min) (5) 1.86 (±0.52) 3.20 (±0.45) 384 (±122)
Moderate (CLc r 31 to 60 mL/min) (4) 4.12 (±1.83) 3.75 (±0.50) 108 (±57)
Severe (CLc r 10 to 30 mL/min) (6) 3.93 (±0.92) 4.01 (±1.10) 130 (±90)

Pediatrics

After administration of a single oral GLUCOPHAGE® (metformin hydrochloride) 500 mg tablet with food, geometric mean metformin Cmax and AUC differed <5% between pediatric type 2 diabetic patients (12 to 16 years of age) and gender- and weight-matched healthy adults (20 to 45 years of age), all with normal renal function.

After administration of a single oral glyburide and metformin hydrochloride tablet with food, dose-normalized geometric mean glyburide Cmax and AUC in pediatric patients with type 2 diabetes (11 to 16 years of age, n=28, mean body weight of 97 kg) differed <6% from historical values in healthy adults.

Gender

There is no information on the effect of gender on the pharmacokinetics of glyburide.

Metformin pharmacokinetic parameters did not differ significantly in subjects with or without type 2 diabetes when analyzed according to gender (males=19, females=16). Similarly, in controlled clinical studies in patients with type 2 diabetes, the antihyperglycemic effect of metformin was comparable in males and females.

Race

No information is available on race differences in the pharmacokinetics of glyburide.

No studies of metformin pharmacokinetic parameters according to race have been performed. In controlled clinical studies of metformin in patients with type 2 diabetes, the antihyperglycemic effect was comparable in whites (n=249), blacks (n=51), and Hispanics (n=24).

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