RiteMED Metformin HCl Warnings

Sustained-release tablet: Warning on Lactic Acidosis: Lactic acidosis is a rare, but serious (high mortality in the absence of prompt treatment), metabolic complication that can occur due to metformin accumulation. Reported cases of lactic acidosis in patients on metformin have occurred primarily in diabetic patients with significant renal failure. The incidence of lactic acidosis can be reduced by also assessing other associated risk factors such as poorly controlled diabetes, ketosis, prolonged fasting, excessive alcohol intake, hepatic insufficiency, and any condition associated with hypoxia.
Lactic acidosis is characterized by elevated blood lactate levels (>5 mmol/L), reduced blood pH, electrolyte disturbance 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 mcg/mL are generally found.
Lactic acidosis is usually accompanied by nonspecific symptoms such as acidotic dyspnea, vomiting, abdominal pain with muscle cramps, and/or a general feeling of malaise with severe fatigue. Hypothermia followed by coma, hypotension, and resistant bradyarrhythmias may be seen with marked acidosis. Instruct patients to immediately alert their physicians if these symptoms occur. Serum electrolytes, ketones, blood glucose, and if indicated, blood pH, lactate levels, and even blood metformin levels may be useful.
Lactic acidosis is a medical emergency that must be treated in a hospital setting. In a patient with lactic acidosis who is taking metformin, the drug should be discontinued immediately and general supportive measures promptly instituted. Because metformin HCl is dialyzable, prompt hemodialysis is recommended to correct the acidosis and remove the accumulated metformin. Such management often results in prompt reversal of symptoms and recovery.
Do not use metformin in patients with congestive heart failure receiving drugs such as digoxin and furosemide because of the risk of hypoperfusion and hypoxemia which may lead to lactic acidosis.