What are the considerations for initiating metformin (Metformin) extended release in an elderly patient?

From the Guidelines

When starting an elderly patient on metformin XR, begin with a low dose of 500 mg once daily with the evening meal, then gradually increase to minimize gastrointestinal side effects, as recommended by the most recent guidelines 1. The target dose for most elderly patients is 1000-1500 mg daily, not exceeding 2000 mg daily. Before initiating therapy, it is essential to check renal function with eGFR, as dose adjustments are needed for eGFR below 45 mL/min/1.73m², and metformin is contraindicated if eGFR is below 30 1. Some key points to consider when prescribing metformin to elderly patients include:

• Monitoring renal function every 3-6 months during treatment 1
• Advising patients to take the medication with food, maintain adequate hydration, and temporarily discontinue metformin during acute illness, surgery, or procedures requiring contrast dye 1
• Being aware of common side effects, such as diarrhea, nausea, and abdominal discomfort, which often improve with time 1
• Considering the extended-release formulation, metformin XR, which allows once-daily dosing and causes fewer gastrointestinal side effects than immediate-release versions, improving adherence and tolerability in this population 1
• Periodically testing vitamin B12 levels in patients taking metformin long-term, as it may be associated with increased risk of vitamin B12 deficiency 1

From the FDA Drug Label

Age 65 or greater —The risk of metformin-associated lactic acidosis increases with the patient's age because elderly patients have a greater likelihood of having hepatic, renal, or cardiac impairment than younger patients. Assess renal function more frequently in elderly patients In patients at risk for the development of renal impairment (e.g., the elderly), renal function should be assessed more frequently. Limited data from controlled pharmacokinetic studies of metformin hydrochloride tablets in healthy elderly subjects suggest that total plasma clearance of metformin is decreased, the half-life is prolonged, and C max is increased, compared to healthy young subjects

Starting an elderly patient on metformin XR requires caution. The patient's renal function should be assessed before initiating metformin hydrochloride tablets, and more frequently than in younger patients, due to the increased risk of metformin-associated lactic acidosis in the elderly. The estimated glomerular filtration rate (eGFR) should be obtained, and metformin hydrochloride tablets are contraindicated in patients with an eGFR less than 30 mL/min/1.73 m^2.

• Monitor renal function: Assess eGFR at least annually in all patients taking metformin hydrochloride tablets, and more frequently in patients at risk for the development of renal impairment, such as the elderly.
• Assess the risk of lactic acidosis: Consider the patient's age, renal function, and other risk factors for lactic acidosis, such as hepatic impairment, cardiac impairment, and other medical conditions.
• Dose adjustment: Consider dose adjustment based on renal function, as metformin is substantially excreted by the kidney. 2 2

From the Research

Considerations for Starting Elderly Patients on Metformin XR

• When starting elderly patients on metformin XR, it is essential to consider their age, body habitus, and physical activity, as these factors play a role in the pathogenesis of hyperglycemia associated with diabetes mellitus 3.
• The use of metformin as a treatment should be avoided in patients over 80 years of age because of declining kidney function 3.
• Metformin is the drug of choice for initiating oral anti-diabetic drug therapy in most cases, and it is crucial to know how to start, titrate, and intensify metformin therapy in primary care 4.

Glycemic Control and Metformin

• Metformin can be used in combination with other medications, such as sulfonylurea, to achieve glycemic control in patients with type 2 diabetes 5, 6, 7.
• The addition of metformin to sulfonylurea therapy can reduce HbA(1c) levels and fasting plasma glucose in patients with inadequately controlled type 2 diabetes 5.
• Metformin plus sulfonylurea was associated with a significant reduction in LDL cholesterol 5.

Special Considerations for Elderly Patients

• Elderly patients with diabetes may have impaired physical function, an increased rate of injurious falls, and increased prevalence of pressure ulcers, amputations, and tuberculosis 3.
• Depression, impaired cognitive function, and lack of recognition of thirst and subsequent dehydration are essential factors to consider in the management of older diabetic patients 3.
• Care providers play a crucial role in the management of older people with diabetes mellitus, and glycemic control can be obtained with minimal side-effects in most older diabetics, including those patients in nursing homes 3.