Metformin is a commonly prescribed medication for managing type 2 diabetes. It helps the body use its own insulin more effectively and reduces the amount of glucose produced by the liver. Understanding potential interactions maintains its effectiveness and patient safety.
Prescription Medications to Be Aware Of
Metformin can interact with various prescription medications, potentially leading to altered blood sugar control or an increased risk of side effects like lactic acidosis. Lactic acidosis, a rare but serious condition, occurs when lactic acid builds up in the blood, and metformin use can increase its production while other factors can decrease its clearance.
Diuretics are drugs used to reduce fluid and treat high blood pressure. Some diuretics can raise blood sugar levels, making metformin less effective. Others, like carbonic anhydrase inhibitors, can increase the risk of lactic acidosis when combined with metformin.
Corticosteroids are anti-inflammatory medications that can increase blood sugar levels. This effect can counteract metformin’s glucose-lowering action, potentially leading to elevated blood glucose. If a corticosteroid is started or stopped while on metformin, blood glucose monitoring is recommended, and dosage may need adjustment.
Certain blood pressure medications, specifically Angiotensin-Converting Enzyme (ACE) inhibitors and Angiotensin Receptor Blockers (ARBs), may increase metformin’s effects and raise the risk of low blood sugar. This interaction is concerning when kidney function is impaired, as it can contribute to metformin accumulation and increase the risk of lactic acidosis.
Thyroid medications, such as levothyroxine used to treat hypothyroidism, can also have an impact. While the exact mechanism is not fully understood, some studies suggest that metformin can lower thyroid-stimulating hormone (TSH) levels, which might necessitate an adjustment in thyroid hormone dosage.
Over-the-Counter Drugs and Supplements
Non-prescription medications and dietary supplements can also interact with metformin.
Nonsteroidal anti-inflammatory drugs (NSAIDs) can affect kidney function. Since metformin is primarily cleared by the kidneys, impaired kidney function can lead to metformin accumulation, increasing the risk of side effects, including lactic acidosis.
Cold and flu remedies often contain ingredients that can interfere with blood glucose control and reduce metformin’s effectiveness. These medications may elevate blood sugar levels, requiring careful monitoring and potential adjustments to diabetes medication dosages.
Some dietary supplements and herbal remedies may affect blood sugar levels or interact with metformin’s actions. Certain supplements can increase the risk of low blood sugar when taken with metformin. Others may also lower blood glucose, potentially leading to hypoglycemia. Limited scientific data exists on herbal remedy interactions, so exercise caution.
Medical Procedures and Lifestyle Factors
Specific medical procedures and lifestyle choices can also influence how metformin affects the body.
Medical imaging procedures using iodinated contrast dyes require temporary discontinuation of metformin. Contrast dyes can cause temporary kidney strain, leading to metformin accumulation and increased lactic acidosis risk if kidney function is compromised. Metformin is typically withheld for 48 hours after the procedure and restarted once kidney function is confirmed normal.
Alcohol consumption is another lifestyle factor with metformin. Excessive alcohol intake increases the risk of lactic acidosis. Both metformin and alcohol can affect lactate metabolism, contributing to lactic acid buildup. Alcohol can also affect blood sugar levels, causing either low or high blood sugar, and can exacerbate gastrointestinal side effects and vitamin B12 deficiency associated with metformin.
When to Consult Your Doctor
Maintain open communication with healthcare providers regarding potential interactions. Always inform your doctor and pharmacist about all medications you are taking, including prescription drugs, over-the-counter remedies, vitamins, and herbal supplements. This helps them assess potential interactions and ensure your treatment plan is safe and effective.
Symptoms signaling a serious interaction, such as lactic acidosis, can be subtle and warrant immediate medical attention. These include:
Unusual weakness or tiredness
Severe muscle pain
Difficulty breathing
Stomach discomfort
Nausea
Vomiting
Unusual sleepiness
If any of these symptoms occur, seek emergency medical help.