METFORMIN HYDROCHLORIDE EXTENDED RELEASE

Metformin hydrochloride extended release tablets USP is an oral antihyperglycemic drug used in the management of type 2 diabetes. Metformin hydrochloride (N,N-dimethylimidodicar- bonimidic diamide hydrochloride) is not chemically or pharmacologically related to any other classes of oral antihyperglycemic agents. The structural formula is as shown: [Structural Formula] Metformin hydrochloride is a white to off-white crystalline compound with a molecular formula of C4H11N5• HCl and a molecular weight of 165.63. Metformin hydrochloride is freely soluble in water and is practically insoluble in acetone, ether, and chloroform. The pKa of metformin is 12.4. The pH of a 1% aqueous solution of metformin hydrochloride is 6.68. Metformin hydrochloride extended release tablets USP contain 500 mg of metformin hydrochloride USP as the active ingredient. Metformin hydrochloride extended release tablets USP 500 mg contain the inactive ingredients sodium carboxymethyl cellulose, hypromellose and magnesium stearate. Metformin hydrochloride extended release tablets USP 500 mg meets USP dissolution Test 3. System Components and Performance- Metformin hydrochloride extended release tablets USP comprises a swellable matrix system. In the aqueous gastrointestinal (GI) environment, the dosage form swells remarkably thereby increasing in size and geometry from where drug is released slowly by a process of diffusion through the gel matrix that is essentially independent of pH. The hydrated polymer system is not rigid and is expected to be broken up by normal peristalsis in the GI tract. The biologically inert components of the tablet may occasionally remain intact during GI transit and will be eliminated in the feces as a soft, hydrated mass.

Metformin hydrochloride extended release tablets USP are indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus.

There is no fixed dosage regimen for the management of hyperglycemia in patients with type 2 diabetes with metformin hydrochloride extended release tablets USP or any other pharmacologic agent. Dosage of metformin hydrochloride extended release tablets USP must be individualized on the basis of both effectiveness and tolerance, while not exceeding the maximum recommended daily doses. The maximum recommended daily dose of metformin hydrochloride extended release tablets USP in adults is 2000 mg. Metformin hydrochloride extended release tablets USP should generally be given once daily with the evening meal. Metformin hydrochloride extended release tablets USP should be started at a low dose, with gradual dose escalation, both to reduce gastrointestinal side effects and to permit identification of the minimum dose required for adequate glycemic control of the patient. During treatment initiation and dose titration (see RECOMMENDED DOSING SCHEDULE), fasting plasma glucose should be used to determine the therapeutic response to metformin hydrochloride extended release tablets USP and identify the minimum effective dose for the patient. Thereafter, glycosylated hemoglobin should be measured at intervals of approximately three months. The therapeutic goal should be to decrease both fasting plasma glucose and glycosylated hemoglobin levels to normal or near normal by using the lowest effective dose of metformin hydrochloride extended release tablets USP, either when used as monotherapy or in combination with sulfonylurea or insulin. Monitoring of blood glucose and glycosylated hemoglobin will also permit detection of primary failure, i.e., inadequate lowering of blood glucose at the maximum recommended dose of medication, and secondary failure, i.e., loss of an adequate blood glucose lowering response after an initial period of effectiveness. Short-term administration of metformin hydrochloride extended release tablets USP may be sufficient during periods of transient loss of control in patients usually well-controlled on diet alone. Metformin hydrochloride extended release tablets USP must be swallowed whole and never crushed or chewed. Occasionally, the inactive ingredients of metformin hydrochloride extended release tablets USP will be eliminated in the feces as a soft, hydrated mass. (See PATIENT INFORMATION printed below.)

Metformin hydrochloride are contraindicated in patients with: Renal disease or renal dysfunction (e.g., as suggested by serum creatinine levels ≥1.5 mg/dL [males], ≥1.4 mg/dL [females] or abnormal creatinine clearance) which may also result from conditions such as cardiovascular collapse (shock), acute myocardial infarction, and septicemia (see WARNINGS and PRECAUTIONS). Known hypersensitivity to metformin hydrochloride. Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma. Diabetic ketoacidosis should be treated with insulin. Metformin hydrochloride should be temporarily discontinued in patients undergoing radiologic studies involving intravascular administration of iodinated contrast materials, because use of such products may result in acute alteration of renal function. (See also PRECAUTIONS.)

In worldwide clinical trials over 900 patients with type 2 diabetes have been treated with metformin hydrochloride extended release tablets USP in placebo- and active-controlled studies. In placebo-controlled trials, 781 patients were administered metformin hydrochloride extended release tablets USP and 195 patients received placebo. Adverse reactions reported in greater than 5% of the metformin hydrochloride extended release tablets USP patients, and that were more common in metformin hydrochloride extended release tablets USP - than placebo-treated patients, are listed in Table 12. Table 12: Most Common Adverse Reactions (>5.0 Percent) in Placebo-Controlled Studies of Metformin Hydrochloride Extended Release Tablets USP* Metformin Hydrochloride Extended Release Tablets USP (n=781) Placebo (n=195) Adverse Reaction % of Patients Diarrhea 9.6 2.6 Nausea/Vomiting 6.5 1.5 *Reactions that were more common in metformin hydrochloride extended release tablets USP - than placebo-treated patients. Diarrhea led to discontinuation of study medication in 0.6% of patients treated with metformin hydrochloride extended release tablets USP. Additionally, the following adverse reactions were reported in ≥1.0% - ≤5.0% of metformin hydrochloride extended release tablets USP patients and were more commonly reported with metformin hydrochloride extended release tablets USP than placebo: abdominal pain, constipation, distention abdomen, dyspepsia/heartburn, flatulence, dizziness, headache, upper respiratory infection, taste disturbance.

(Clinical Evaluation of Drug Interactions Conducted with Metformin Hydrochloride Tablets) Glyburide - In a single-dose interaction study in type 2 diabetes patients, coadministration of metformin and glyburide did not result in any changes in either metformin pharmacokinetics or pharmacodynamics. Decreases in glyburide AUC and Cmax were observed, but were highly variable. The single-dose nature of this study and the lack of correlation between glyburide blood levels and pharmacodynamic effects, makes the clinical significance of this interaction uncertain (see DOSAGE AND ADMINISTRATION: CONCOMITANT METFORMIN HYDROCHLORIDE EXTENDED RELEASE TABLETS USP AND ORAL SULFONYLUREA THERAPY IN ADULT PATIENTS). Furosemide - A single-dose, metformin-furosemide drug interaction study in healthy subjects demonstrated that pharmacokinetic parameters of both compounds were affected by coadministration. Furosemide increased the metformin plasma and blood Cmax by 22% and blood AUC by 15%, without any significant change in metformin renal clearance. When administered with metformin, the Cmax and AUC of furosemide were 31% and 12% smaller, respectively, than when administered alone, and the terminal half-life was decreased by 32%, without any significant change in furosemide renal clearance. No information is available about the interaction of metformin and furosemide when coadministered chronically. Nifedipine - A single-dose, metformin-nifedipine drug interaction study in normal healthy volunteers demonstrated that coadministration of nifedipine increased plasma metformin Cmax and AUC by 20% and 9%, respectively, and increased the amount excreted in the urine. Tmax and half-life were unaffected. Nifedipine appears to enhance the absorption of metformin. Metformin had minimal effects on nifedipine. Cationic drugs - Cationic drugs (e.g., amiloride, digoxin, morphine, procainamide, quinidine, quinine, ranitidine, triamterene, trimethoprim, or vancomycin) that are eliminated by renal tubular secretion theoretically have the potential for interaction with metformin by competing for common renal tubular transport systems. Such interaction between metformin and oral cimetidine has been observed in normal healthy volunteers in both single- and multiple-dose, metformin-cimetidine drug interaction studies, with a 60% increase in peak metformin plasma and whole blood concentrations and a 40% increase in plasma and whole blood metformin AUC. There was no change in elimination half-life in the single-dose study. Metformin had no effect on cimetidine pharmacokinetics. Although such interactions remain theoretical (except for cimetidine), careful patient monitoring and dose adjustment of metformin hydrochloride extended release tablets USP and/or the interfering drug is recommended in patients who are taking cationic medications that are excreted via the proximal renal tubular secretory system. Other - Certain drugs tend to produce hyperglycemia and may lead to loss of glycemic control. These drugs include the thiazides and other diuretics, corticosteroids, phenothiazines, thyroid products, estrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, calcium channel blocking drugs, and isoniazid. When such drugs are administered to a patient receiving metformin hydrochloride extended release tablets USP, the patient should be closely observed for loss of blood glucose control. When such drugs are withdrawn from a patient receiving metformin hydrochloride extended release tablets USP, the patient should be observed closely for hypoglycemia. In healthy volunteers, the pharmacokinetics of metformin and propranolol, and metformin and ibuprofen were not affected when coadministered in single-dose interaction studies. Metformin is negligibly bound to plasma proteins and is, therefore, less likely to interact with highly protein-bound drugs such as salicylates, sulfonamides, chloramphenicol, and probenecid, as compared to the sulfonylureas, which are extensively bound to serum proteins.