Advanced hypoglycemic drug regimens: metformin combination therapy, advantages of sustained-release formulations, and the application of thiazolidinediones.

Why should underweight diabetic patients not take metformin?

Metformin can improve insulin resistance and also has lipid-lowering and weight-reducing effects, making it a first-line drug for obese type 2 diabetic patients. However, underweight patients should not take metformin because it suppresses appetite and reduces weight, leading to further weight loss, malnutrition, and weakened immunity.

What are the interactions between metformin and other drugs?
① When used in combination with insulin, its blood sugar-lowering effect is enhanced, therefore the dosage should be adjusted.

② When used with anticoagulants, it can enhance the anticoagulant effect, leading to bleeding tendency.

③ Long-term use can reduce intestinal absorption of vitamin B₁₂, resulting in decreased hemoglobin. ④ When used in combination with cimetidine, nifedipine, etc., severe stomach discomfort, extreme fatigue, weakness, muscle pain, dyspnea, chills, dizziness, and even bradycardia or arrhythmia may occur.

Does metformin increase the incidence of coronary heart disease? There is academic debate regarding whether metformin increases the mortality rate of diabetes. However, the UK Prospective Diabetes Study showed that metformin does not increase diabetes-related mortality. Metformin, used alone or in combination with other hypoglycemic agents, does not increase the incidence of myocardial infarction or stroke; in fact, it can reduce the incidence of cardiovascular disease, diabetes-related heart rate, and overall mortality in patients with type 2 diabetes.

Which hypoglycemic drugs can be used in combination with metformin? What are the effects?

① Metformin combined with sulfonylureas: This combination can control blood glucose in 60%–70% of type 2 diabetes patients with a baseline HbA1c of 9.0%, and can also reduce the risk of diabetes-related death.

② Metformin combined with alpha-glucosidase inhibitors: This combination can comprehensively control both fasting and postprandial blood glucose. Multicenter randomized double-blind controlled studies have shown that this combination can reduce HbA1c by 0.65%, lower fasting and postprandial blood glucose, and significantly reduce plasma insulin levels compared to placebo, without weight gain. This combination is safe and effective.

③ Metformin combined with thiazolidinediones: This combination not only improves glucose metabolism but also significantly reduces weight and blood pressure. Domestic reports indicate that for obese type 2 diabetes patients with a disease duration of more than 5 years, combined treatment with metformin and insulin can effectively control blood sugar, reduce body mass index, lower triglycerides and free fatty acids, and significantly improve insulin resistance.

④ Metformin combined with insulin: This not only enhances the hypoglycemic effect and reduces blood sugar fluctuations, but also reduces insulin dosage and alleviates insulin-induced weight gain. Studies have confirmed that only metformin can control weight while improving glycated hemoglobin. Combined use with insulin can reduce insulin dosage by 15%–100%, lower hyperglycemia by up to 30%, and prevent weight gain. Some domestic scholars have reported that combined use can also shorten the time to achieve target blood sugar levels.

What about the use of metformin in the elderly and diabetic patients over 10 years of age?

Whether metformin is suitable for the elderly remains controversial because age-related decline in glomerular filtration rate is very common, easily leading to drug accumulation in the body. Studies have shown that metformin treatment in elderly patients over 70 years of age with mild renal impairment did not increase serum lactate levels. This is because metformin itself does not increase lactate concentration in the body; tissue hypoxia is the initiating factor for lactic acidosis. Therefore, strict adherence to indications is crucial. In high-risk populations, treatment should begin with a low dose; for elderly patients and those with renal insufficiency, the initial and maximum doses should be only one-third of the normal range. Serum lactate levels should be closely monitored, and the medication should be discontinued if it exceeds 3 mmol/L. Therefore, good blood glucose control can still be achieved in the elderly with relatively good safety. Currently, metformin is approved by the US Food and Drug Administration for monotherapy in patients over 10 years of age, and in combination with sulfonylureas or insulin for patients over 17 years of age with type 2 diabetes.

What issues should be considered when using metformin clinically? ① Gradually increase the dose. General recommendations: If the dosage is 500mg, once daily, it can be taken with breakfast; if the dosage is 500mg, twice daily, one tablet each with breakfast and dinner; if the dosage is 500mg, three times daily, it can be taken twice daily (breakfast and dinner) or three times daily (breakfast, lunch, and dinner). The maximum daily dose of metformin should not exceed 2500mg. Considering the body size and weight of Chinese people, it is recommended that the maximum daily dose not exceed 2000mg.

② Taking it with meals can reduce gastrointestinal side effects.

③ Regularly check serum creatinine, liver function, and urine ketones.

④ If contraindications are found, discontinue use immediately.

⑤ Effects of other drugs, such as cimetidine (Cimicifuga), can reduce the renal excretion of metformin; drugs containing agar can reduce the absorption of metformin.

What are the advantages of metformin extended-release tablets?

Among biguanide oral hypoglycemic agents, metformin has been proven to be an effective treatment for patients with type 2 diabetes. The mechanism of action of metformin in controlling blood glucose in patients with type 2 diabetes is as follows: metformin enhances the sensitivity of the liver and peripheral tissues (especially skeletal muscle) to insulin, reduces hepatic gluconeogenesis, and promotes the absorption of glucose by peripheral tissues. Pharmacokinetic studies have shown that traditional metformin immediate-release tablets are mostly absorbed in the upper gastrointestinal tract, with only a small portion absorbed in the colon. As gastrointestinal motility slows down, the absorption range increases. The new formulation of metformin extended-release tablets swells after absorbing water, releasing the active drug through hydrated polymers, prolonging the residence time in the stomach, thus slowing down the absorption of the drug in the upper gastrointestinal tract, allowing for once-daily dosing. In healthy volunteers, by measuring the area under the concentration-time curve (AUC), the absorption rate of once-daily metformin extended-release tablets is similar to that of twice-daily metformin immediate-release tablets with the same total dose. The mean steady-state area under the curve (AUC) of 2000 mg metformin extended-release tablets once daily and 1000 mg metformin immediate-release tablets twice daily was the same (20.5 μg·h/ml), indicating that the once-daily metformin extended-release regimen is feasible and improves patient adherence, superior to traditional metformin immediate-release tablets. Reducing the frequency of dosing is more suitable for long-term medication adherence. Improving medication adherence in diabetic patients will lead to better blood glucose control and reduce the risk of long-term diabetes-related complications.