GLUCOVANCE

In double-blind clinical trials involving GLUCOVANCE as initial therapy or as second-line therapy, a total of 642 patients received GLUCOVANCE, 312 received metformin therapy, 324 received glyburide therapy, and 161 received placebo. The percent of patients reporting events and types of adverse events reported in clinical trials of GLUCOVANCE (all strengths) as initial therapy and second-line therapy are listed in Table 6.

Table 6: Most Common Clinical Adverse Events ( > 5 Percent) in Double-Blind Clinical Studies of GLUCOVANCE Used as Initial or Second-Line Therapy

In a controlled clinical trial of rosiglitazone versus placebo in patients treated with GLUCOVANCE (n=365), 181 patients received GLUCOVANCE with rosiglitazone and 184 received GLUCOVANCE with placebo.

Edema was reported in 7.7% (14/181) of patients treated with rosiglitazone compared to 2.2% (4/184) of patients treated with placebo. A mean weight gain of 3 kg was observed in rosiglitazone-treated patients.

Disulfiram-like reactions have very rarely been reported in patients treated with glyburide tablets.

Hypoglycemia

In controlled clinical trials of GLUCOVANCE there were no hypoglycemic episodes requiring medical intervention and/or pharmacologic therapy; all events were managed by the patients. The incidence of reported symptoms of hypoglycemia (such as dizziness, shakiness, sweating, and hunger), in the initial therapy trial of GLUCOVANCE are summarized in Table 7. The frequency of hypoglycemic symptoms in patients treated with GLUCOVANCE 1.25 mg/250 mg was highest in patients with a baseline HbA_1c < 7%, lower in those with a baseline HbA_1c of between 7% and 8%, and was comparable to placebo and metformin in those with a baseline HbA_1c > 8%. For patients with a baseline HbA_1c between 8% and 11% treated with GLUCOVANCE 2.5 mg/500 mg as initial therapy, the frequency of hypoglycemic symptoms was 30 to 35%. As second-line therapy in patients inadequately controlled on sulfonylurea alone, approximately 6.8% of all patients treated with GLUCOVANCE experienced hypoglycemic symptoms. When rosiglitazone was added to GLUCOVANCE therapy, 22% of patients reported one or more fingerstick glucose measurements ≤ 50 mg/dL compared to 3.3% of placebo-treated patients. All hypoglycemic events were managed by the patients and only one patient discontinued for hypoglycemia. (See PRECAUTIONS: General: Addition of Thiazolidinediones to GLUCOVANCE Therapy.)

Gastrointestinal Reactions

The incidence of GI side effects (diarrhea, nausea/vomiting, and abdominal pain) in the initial therapy trial are summarized in Table 7. Across all GLUCOVANCE trials, GI symptoms were the most common adverse events with GLUCOVANCE and were more frequent at higher dose levels. In controlled trials, < 2% of patients discontinued GLUCOVANCE therapy due to GI adverse events.

Table 7: Treatment Emergent Symptoms of Hypoglycemia or Gastrointestinal Adverse Events in a Placebo- and Active-Controlled Trial of GLUCOVANCE as Initial Therapy

GLUCOVANCE

Certain drugs tend to produce hyperglycemia and may lead to loss of blood glucose 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 GLUCOVANCE, the patient should be closely observed for loss of blood glucose control. When such drugs are withdrawn from a patient receiving GLUCOVANCE, the patient should be observed closely for hypoglycemia. 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 sulfonylureas, which are extensively bound to serum proteins.

Glyburide

The hypoglycemic action of sulfonylureas may be potentiated by certain drugs including nonsteroidal anti-inflammatory agents and other drugs that are highly protein bound, salicylates, sulfonamides, chloramphenicol, probenecid, coumarins, monoamine oxidase inhibitors, and beta adrenergic blocking agents. When such drugs are administered to a patient receiving GLUCOVANCE, the patient should be observed closely for hypoglycemia. When such drugs are withdrawn from a patient receiving GLUCOVANCE, the patient should be observed closely for loss of blood glucose control.

A possible interaction between glyburide and ciprofloxacin, a fluoroquinolone antibiotic, has been reported, resulting in a potentiation of the hypoglycemic action of glyburide. The mechanism for this interaction is not known.

A potential interaction between oral miconazole and oral hypoglycemic agents leading to severe hypoglycemia has been reported. Whether this interaction also occurs with the intravenous, topical, or vaginal preparations of miconazole is not known.

Metformin Hydrochloride

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 GLUCOVANCE 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

In healthy volunteers, the pharmacokinetics of metformin and propranolol and metformin and ibuprofen were not affected when coadministered in single-dose interaction studies.

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