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Riomet

Generic Name: Metformin Hydrochloride (Tablet)
Drug Category: Biguanide
Litigation Alert Level: Medium
This drug has been approved for use by males and females over the age of 10 years old for a maximum duration of 29 weeks.

Approved Uses

Indicated as an adjunct to diet and exercise to improve glycemic control in adults and pediatric patients 10 years of age and older with type 2 diabetes mellitus.

There have been no clinical studies establishing conclusive evidence of macrovascular risk reduction with RIOMET or any other oral anti-diabetic drug.

If patients have not responded to four weeks of the maximum dose of RIOMET monotherapy, consideration should be given to gradual addition of an oral sulfonylurea while continuing RIOMET at the maximum dose, even if prior primary or secondary failure to a sulfonylurea has occurred.

If patients have not satisfactorily responded to one to three months of concomitant therapy with the maximum dose of RIOMET and the maximum dose of an oral sulfonylurea, consider therapeutic alternatives including switching to insulin with or without RIOMET.

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.

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. If metformin-associated lactic acidosis is suspected, immediately discontinue RIOMET and institute general supportive measures in a hospital setting. Prompt hemodialysis is recommended.

Hypoglycemia does not occur in patients receiving metformin alone under usual circumstances of use, but could occur when caloric intake is deficient, when strenuous exercise is not compensated by caloric supplementation, or during concomitant use with other glucose-lowering agents (such as sulfonylureas and insulin) or ethanol.

Elderly, debilitated, or malnourished patients, and those with adrenal or pituitary insufficiency or alcohol intoxication are particularly susceptible to hypoglycemic effects. Hypoglycemia may be difficult to recognize in the elderly, and in people who are taking beta-adrenergic blocking drugs.

RIOMET is contraindicated in patients with:

  • Severe renal impairment (eGFR below 30 mL/min/1.73 m2)
  • Acute or chronic metabolic acidosis, including diabetic ketoacidosis, with or without coma

The risk of metformin accumulation and metformin-associated lactic acidosis increases with the severity of renal impairment because metformin is substantially excreted by the kidney. Clinical recommendations based upon the patient’s renal function include:

  • Before initiating metformin hydrochloride, obtain an estimated glomerular filtration rate (eGFR)
  • Metformin hydrochloride is contraindicated in patients with an eGFR less than 30 mL/min/1.73 m2
  • Initiation of metformin hydrochloride is not recommended in patients with eGFR between 30 to 45 mL/min/1.73 m2
  • Obtain an eGFR at least annually in all patients taking metformin hydrochloride. In patients at risk for the development of renal impairment (e.g., the elderly), renal function should be assessed more frequently.
  • In patients taking metformin hydrochloride whose eGFR falls below 45 mL/min/1.73 m2, assess the benefit and risk of continuing therapy

Discontinue metformin hydrochloride tablets at the time of, or prior to, an iodinated contrast imaging procedure in patients with an eGFR between 30 and 60 mL/min/1.73 m2; in patients with a history of liver disease, alcoholism, or heart failure; or in patients who will be administered intra-arterial iodinated contrast. Re-evaluate eGFR 48 hours after the imaging procedure; restart metformin hydrochloride tablets if renal function is stable.

Decrease to subnormal levels of previously normal serum Vitamin B12 levels, without clinical manifestations.

In patients with decreased renal function, the plasma and blood half-life of metformin is prolonged and the renal clearance is decreased.

Nifedipine appears to enhance the absorption of metformin.

Insulin and insulin secretagogues (e.g., sulfonylurea) are known to cause hypoglycemia. Metformin hydrochloride may increase the risk of hypoglycemia when combined with insulin and/or an insulin secretagogue. Therefore, a lower dose of insulin or insulin secretagogue may be required to minimize the risk of hypoglycemia when used in combination with metformin hydrochloride.

Concomitant use of drugs that interfere with common renal tubular transport systems involved in the renal elimination of metformin (e.g., organic cationic transporter-2 [OCT2] / multidrug and toxin extrusion [MATE] inhibitors such as ranolazine, vandetanib, dolutegravir, and cimetidine) could increase systemic exposure to metformin and may increase the risk for lactic acidosis. Consider the benefits and risks of concomitant use.

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 RIOMET, the patient should be closely observed for loss of blood glucose control.

Topiramate or other carbonic anhydrase inhibitors (e.g., zonisamide, acetazolamide or dichlorphenamide) frequently causes a decrease in serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis. Concomitant use of these drugs with RIOMET may increase the risk for lactic acidosis. Consider more frequent monitoring of these patients.

Alcohol is known to potentiate the effect of metformin on lactate metabolism.

Discuss the potential for unintended pregnancy with premenopausal women as therapy with metformin hydrochloride may result in ovulation in some anovulatory women.

There are no adequate and well-controlled studies in pregnant women with metformin.

Limited published studies report that metformin is present in human milk.  Because the potential for hypoglycemia in nursing infants may exist, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

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Off-label Uses

• Use in patients under the age of 10. GoToSource

• Dosage greater than 2550 mg per day in adults and 2000 mg per day in pediatric patients (10 to 16 years of age). GoToSource

• Non small cell lung cancer. GoToSource

• Polycystic ovary syndrome. GoToSource

• Unexplained oligospermia and azoospermia. GoToSource

• Recurrent miscarriage. GoToSource

• Diastolic dysfunction of metabolic syndrome. GoToSource

• Congenital nephrogenic diabetes insipidus. GoToSource

• Obesity. GoToSource

• Acne. GoToSource

• Anti-aging. GoToSource

• Prediabetes. GoToSource

• Gestational diabetes. GoToSource

• Endometrial hyperplasia. GoToSource

Adverse Events

Lactic acidosis (too much acid in the body). GoToSource

Vitamin B12 deficiency. GoToSource

Hypoglycemia (low blood sugar). GoToSource

Metabolic encephalopathy (metabolic abnormalities adversely affecting brain function). GoToSource

Cognitive impairment. GoToSource

Litigation

Lawsuits filed for cognitive decline. 

The material contained in GoToPills is for informational purposes only and not intended to replace the judgment, evaluation and treatment of physicians, pharmacists and other healthcare providers. GoToPills does not provide medical advice, diagnoses or treatment. Always seek the advice of your physician or other qualified health provider regarding a medical condition or treatment.

 

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Site Last Updated March 29, 2024