WARNING: LACTIC ACIDOSIS Postmarketing cases of metformin-associated lactic acidosis have resulted in death, hypothermia, hypotension, and resistant bradyarrhythmias. The onset of metformin associated lactic acidosis is often subtle, accompanied only by nonspecific symptoms such as malaise, myalgias, respiratory distress, somnolence, and abdominal pain. Metformin-associated lactic acidosis was characterized by elevated blood lactate levels (>5 mmol/Liter), anion gap acidosis (without evidence of ketonuria or ketonemia), an increased lactate/pyruvate ratio; and metformin plasma levels generally >5 mcg/mL (see PRECAUTIONS ). Risk factors for metformin-associated lactic acidosis include renal impairment, concomitant use of certain drugs (e.g. carbonic anhydrase inhibitors such as topiramate), age 65 years old or greater, having a radiological study with contrast, surgery and other procedures, hypoxic states (e.g., acute congestive heart failure), excessive alcohol intake, and hepatic impairment. Steps to reduce the risk of and manage metformin-associated lactic acidosis in these high risk groups are provided (see DOSAGE AND ADMINISTRATION , CONTRAINDICATIONS , and PRECAUTIONS ) . If metformin-associated lactic acidosis is suspected, immediately discontinue metformin hydrochloride extended release tablets USP and institute general supportive measures in a hospital setting. Prompt hemodialysis is recommended (see PRECAUTIONS ) .
ADVERSE REACTIONS 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 * * Reactions that were more common in metformin hydrochloride extended release tablets USP - than placebo-treated patients. 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 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% to ≤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. Cholestatic, hepatocellular, and mixed hepatocellular liver injury have been reported with postmarketing use of metformin.