LACTIC ACIDOSIS Lactic acidosis is a rare, but serious, metabolic complication that can occur due to metformin accumulation during treatment with Glyburide and Metformin Hydrochloride tablets; when it occurs, it is fatal in approximately 50% of cases. Lactic acidosis may also occur in association with a number of pathophysiologic conditions, including diabetes mellitus, and whenever there is significant tissue hypoperfusion and hypoxemia. Lactic acidosis is characterized by elevated blood lactate levels (>5 mmol/L), decreased blood pH, electrolyte disturbances with an increased anion gap, and an increased lactate/pyruvate ratio. When metformin is implicated as the cause of lactic acidosis, metformin plasma levels >5 μg/mL are generally found. The reported incidence of lactic acidosis in patients receiving metformin hydrochloride is very low (approximately 0.03 cases/1000 patient-years, with approximately 0.015 fatal cases/1000 patient-years). In more than 20,000 patient-years exposure to metformin in clinical trials, there were no reports of lactic acidosis. Reported cases have occurred primarily in diabetic patients with significant renal insufficiency, including both intrinsic renal disease and renal hypoperfusion, often in the setting of multiple concomitant medical/surgical problems and multiple concomitant medications. Patients with congestive heart failure requiring pharmacologic management, in particular those with unstable or acute congestive heart failure who are at risk of hypoperfusion and hypoxemia, are at increased risk of lactic acidosis. The risk of lactic acidosis increases with the degree of renal dysfunction and the patient’s age. The risk of lactic acidosis may, therefore, be significantly decreased by regular monitoring of renal function in patients taking metformin and by use of the minimum effective dose of metformin. In particular, treatment of the elderly should be accompanied by careful monitoring of renal function. A combination of Glyburide and Metformin Hydrochloride treatment should not be initiated in patients > 80 years of age unless measurement of creatinine clearance demonstrates that renal function is not reduced, as these patients are more susceptible to developing lactic acidosis. In addition, Glyburide and Metformin Hydrochloride should be promptly withheld in the presence of any condition associated with hypoxemia, dehydration, or sepsis. Because impaired hepatic function may significantly limit the ability to clear lactate, Glyburide and Metformin Hydrochloride should generally be avoided in patients with clinical or laboratory evidence of hepatic disease. Patients should be cautioned against excessive alcohol intake, either acute or chronic, when taking Glyburide and Metformin Hydrochloride, since alcohol potentiates the effects of metformin hydrochloride on lactate metabolism. In addition, Glyburide and Metformin Hydrochloride should be temporarily discontinued prior to any intravascular radiocontrast study and for any surgical procedure (see also PRECAUTIONS ). The onset of lactic acidosis often is subtle, and accompanied only by nonspecific symptoms such as malaise, myalgias, respiratory distress, increasing somnolence, and nonspecific abdominal distress. There may be associated hypothermia, hypotension, and resistant bradyarrhythmias with more marked acidosis. The patient and the patient’s physician must be aware of the possible importance of such symptoms and the patient should be instructed to notify the physician immediately if they occur (see also PRECAUTIONS ). Glyburide and Metformin Hydrochloride should be withdrawn until the situation is clarified. Serum electrolytes, ketones, blood glucose, and if indicated, blood pH, lactate levels, and even blood metformin levels may be useful. Once a patient is stabilized on any dose level of Glyburide and Metformin Hydrochloride, gastrointestinal symptoms, which are common during initiation of therapy with metformin, are unlikely to be drug related. Later occurrence of gastrointestinal symptoms could be due to lactic acidosis or other serious disease. Levels of fasting venous plasma lactate above the upper limit of normal but less than 5 mmol/L in patients taking Glyburide and Metformin Hydrochloride do not necessarily indicate impending lactic acidosis and may be explainable by other mechanisms, such as poorly controlled diabetes or obesity, vigorous physical activity, or technical problems in sample handling. (See also PRECAUTIONS .) Lactic acidosis should be suspected in any diabetic patient with metabolic acidosis lacking evidence of ketoacidosis (ketonuria and ketonemia). Lactic acidosis is a medical emergency that must be treated in a hospital setting. In a patient with lactic acidosis who is taking Glyburide and Metformin Hydrochloride, the drug should be discontinued immediately and general supportive measures promptly instituted. Because metformin hydrochloride is dialyzable (with a clearance of up to 170 mL/min under good hemodynamic conditions), prompt hemodialysis is recommended to correct the acidosis and remove the accumulated metformin. Such management often results in prompt reversal of symptoms and recovery. (See also CONTRAINDICATIONS and PRECAUTIONS .)
ADVERSE REACTIONS Glyburide and Metformin Hydrochloride In double-blind clinical trials involving Glyburide and Metformin Hydrochloride as initial therapy or as second-line therapy, a total of 642 patients received the combination product Glyburide and Metformin Hydrochloride, 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 Glyburide and Metformin Hydrochloride (all strengths) as initial therapy and second-line therapy are listed in Table 6 . Table 6: Most Common Clinical Adverse Events (>5 %) in Double-Blind Clinical Studies of Glyburide and Metformin Hydrochloride Used as Initial or Second-Line Therapy Number (%) of Patients Glyburide and Metformin Adverse Event Placebo Glyburide Metformin Hydrochloride N=161 N=324 N=312 N=642 Upper respiratory infection 22 (13.7) 57 (17.6) 51 (16.3) 111 (17.3) Diarrhea 9 (5.6) 20 (6.2) 64 (20.5) 109 (17.0) Headache 17 (10.6) 37 (11.4) 29 (9.3) 57 (8.9) Nausea/vomiting 10 (6.2) 17 (5.2) 38 (12.2) 49 (7.6) Abdominal pain 6 (3.7) 10 (3.1) 25 (8.0) 44 (6.9) Dizziness 7 (4.3) 18 (5.6) 12 (3.8) 35 (5.5) In a controlled clinical trial of rosiglitazone versus placebo in patients treated with Glyburide and Metformin Hydrochloride (n=365), 181 patients received Glyburide and Metformin Hydrochloride with rosiglitazone and 184 received Glyburide and Metformin Hydrochloride 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 Glyburide and Metformin Hydrochloride 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 Glyburide and Metformin Hydrochloride are summarized in Table 7 . The frequency of hypoglycemic symptoms in patients treated with Glyburide and Metformin Hydrochloride 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 Glyburide and Metformin Hydrochloride 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 Glyburide and Metformin Hydrochloride experienced hypoglycemic symptoms. When rosiglitazone was added to Glyburide and Metformin Hydrochloride 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 Glyburide and Metformin Hydrochloride Therapy .) Gastrointestinal Reactions The incidence of gastrointestinal (GI) side effects (diarrhea, nausea/vomiting, and abdominal pain) in the initial therapy trial are summarized in Table 7 . Across all Glyburide and Metformin Hydrochloride trials, GI symptoms were the most common adverse events with Glyburide and Metformin Hydrochloride and were more frequent at higher dose levels. In controlled trials, <2% of patients discontinued Glyburide and Metformin Hydrochloride 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 Glyburide and Metformin Hydrochloride as Initial Therapy Glyburide and Glyburide and Metformin Metformin Hydrochloride Hydrochloride Placebo Glyburide Metformin 1.25 mg/250 mg 2.5 mg/500 mg Variable Tablets Tablets Tablets Tablets N=161 N=160 N=159 N=158 N=162 Mean Final Dose 0 mg 5.3 mg 1317 mg 2.78 mg/557 mg 4.1 mg/824 mg Number (%) of patients with symptoms of hypoglycemia 5 (3.1) 34 (21.3) 5 (3.1) 18 (11.4) 61 (37.7) Number (%) of patients with gastrointestinal adverse events 39 (24.2) 38 (23.8) 69 (43.3) 50 (31.6) 62 (38.3)