Metformin prescribing information
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Comprehensive Overview of Metformin Prescribing Information
Benefits of Metformin
Metformin is primarily prescribed for managing type 2 diabetes mellitus due to its efficacy in lowering blood glucose levels without causing significant weight gain or hypoglycemia. Additionally, metformin has shown potential benefits beyond glucose control, including cardiovascular protection, anti-tumor effects, and neuroprotection. Early treatment with metformin is associated with reduced cardiovascular morbidity and total mortality in newly diagnosed type 2 diabetic patients.
Risks and Adverse Effects
The most common adverse effects of metformin are gastrointestinal issues, such as nausea, vomiting, and diarrhea. A significant concern historically has been the risk of lactic acidosis, particularly in patients with renal insufficiency or heart failure. However, recent analyses suggest that the risk of lactic acidosis is minimal. The FDA guidelines contraindicate metformin use in patients with serum creatinine concentrations ≥1.5 mg/dL in men and ≥1.4 mg/dL in women, although this is debated due to the use of estimated glomerular filtration rate (eGFR) as a more accurate measure of renal function.
Interactions and Necessary Prophylaxis
Metformin can interact with other medications, potentially increasing the risk of adverse effects. It is essential to monitor patients for interactions with drugs that can affect renal function or increase the risk of lactic acidosis. Prophylactic measures include regular monitoring of renal function and vitamin B12 levels, as long-term use of metformin can lead to vitamin B12 deficiency.
Administering and Informing
Metformin is available in immediate-release (IR), extended-release (XR), and delayed-release (DR) formulations. The DR formulation targets the lower bowel to leverage gut-based mechanisms of action, providing effective glycemic control with lower plasma exposure. Patients should be informed about the potential side effects, the importance of adherence to prescribed doses, and the need for regular monitoring of blood glucose levels and renal function.
Monitoring and Stopping
Regular monitoring of blood glucose levels, renal function, and vitamin B12 levels is crucial for patients on metformin therapy. If renal function deteriorates significantly, metformin should be discontinued to prevent the risk of lactic acidosis. Additionally, patients should be monitored for signs of gastrointestinal distress and other adverse effects.
Special Populations
Low-Income and Medicaid-Insured Patients
In low-income and Medicaid-insured patients with prediabetes, metformin prescribing is influenced by sociodemographic characteristics and comorbid conditions such as hypertension and obesity. However, the prevalence of metformin prescription in this population is less than 8%.
Pregnancy
Metformin is increasingly used in pregnant women with type 2 diabetes. Studies indicate that metformin, when added to insulin, can improve glycemic control, reduce maternal weight gain, and lower the required insulin dose. However, it may also result in a higher proportion of small-for-gestational-age infants.
Renal Insufficiency
For patients with mild-to-moderate renal insufficiency, the decision to continue metformin should be based on a careful assessment of renal function using eGFR rather than serum creatinine alone. Discontinuation should be considered if renal function declines significantly.
Conclusion
Metformin remains a cornerstone in the management of type 2 diabetes due to its efficacy, safety profile, and additional benefits beyond glucose control. However, careful consideration of patient-specific factors, regular monitoring, and patient education are essential to optimize its use and minimize risks.
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