Does metformin affect blood pressure
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The Impact of Metformin on Blood Pressure: A Comprehensive Review
Introduction to Metformin and Blood Pressure
Metformin is a widely used medication for managing type 2 diabetes mellitus (T2DM). Beyond its glucose-lowering effects, researchers have investigated its potential impact on blood pressure (BP). This article synthesizes findings from multiple studies to provide a clear understanding of how metformin affects BP in various populations.
Metformin and Orthostatic Blood Pressure in Type 2 Diabetes
A study from the Copenhagen Insulin and Metformin Therapy (CIMT) trial examined the effects of metformin on cardiovascular autonomic neuropathy (CAN) in T2DM patients. The results indicated that metformin, when combined with insulin, increased the early drop in orthostatic blood pressure (OBP). Specifically, there was a significant increase in both systolic and diastolic BP drops compared to placebo, suggesting an adverse effect on OBP recovery1.
Metformin's Effect on Blood Pressure in Nondiabetic Patients
A meta-analysis of randomized controlled trials evaluated the impact of metformin on systolic blood pressure (SBP) and diastolic blood pressure (DBP) in nondiabetic patients. The pooled results showed a significant reduction in SBP by approximately 2 mmHg, particularly in patients with impaired glucose tolerance or obesity. However, no significant effect was observed on DBP2.
Postprandial Blood Pressure Modulation by Metformin
In patients with T2DM, metformin has been shown to attenuate the postprandial fall in BP. A study demonstrated that metformin reduced the hypotensive response to oral glucose intake, which was associated with increased glucagon-like peptide-1 (GLP-1) secretion and delayed gastric emptying. This suggests that metformin may help stabilize BP after meals in T2DM patients3.
Metformin and Salt-Induced Hypertension
Research on spontaneously hypertensive rats indicated that long-term metformin administration blunted the rise in BP caused by a high-salt diet. This effect was attributed to reduced sympathetic neural outflow, highlighting metformin's potential in managing salt-induced hypertension4.
Metformin in Hypertensive, Obese Women
A study involving obese, nondiabetic, hypertensive women found that metformin treatment significantly reduced BP, along with improvements in glucose and lipid metabolism. This suggests that metformin can contribute to a more favorable cardiovascular risk profile in this population5.
Mixed Results in Hypertensive Patients Without Diabetes
Contrary to some findings, a randomized clinical trial reported no significant reduction in BP in hypertensive patients without diabetes after metformin treatment. This trial used ambulatory blood pressure monitoring (ABPM) and found no difference between the metformin and placebo groups, indicating that metformin's BP-lowering effects may not extend to all hypertensive populations9.
Metformin and Endothelial Function in Diabetic Rats
In streptozotocin-induced diabetic rats, metformin treatment reduced BP and improved endothelial function. The study suggested that metformin's effects were mediated through enhanced nitric oxide availability and reduced oxidative stress, contributing to improved vascular health10.
Conclusion
The impact of metformin on blood pressure varies across different populations and conditions. While it shows promise in reducing systolic BP in nondiabetic patients with impaired glucose tolerance or obesity, and in managing postprandial hypotension in T2DM, its effects are not universally observed in all hypertensive individuals. Further research is needed to fully understand the mechanisms and identify the specific patient groups that may benefit most from metformin's BP-lowering properties.
Sources and full results
Most relevant research papers on this topic
Metformin may adversely affect orthostatic blood pressure recovery in patients with type 2 diabetes: substudy from the placebo-controlled Copenhagen Insulin and Metformin Therapy (CIMT) trial
Metformin combined with insulin may increase early drop in orthostatic blood pressure, potentially worsening cardiovascular autonomic neuropathy in type 2 diabetes patients.
RCT
Large Human Trial
Very Rigorous JournalEffects of metformin on blood pressure in nondiabetic patients: a meta-analysis of randomized controlled trials
Metformin effectively lowers systolic blood pressure in nondiabetic patients, especially in those with impaired glucose tolerance or obesity.
Meta-AnalysisVery Rigorous JournalMetformin attenuates the postprandial fall in blood pressure in type 2 diabetes
Metformin acutely reduces the hypotensive response to oral glucose in type 2 diabetes patients, potentially improving their cardiovascular profile.
RCT
Rigorous JournalMetformin attenuates salt-induced hypertension in spontaneously hypertensive rats.
Metformin effectively reduces blood pressure and heart rate in rats with high-salt diet-induced hypertension, enhancing its chronic depressor actions.
RCT
Animal StudyMetformin Improves Glucose, Lipid Metabolism, and Reduces Blood Pressure in Hypertensive, Obese Women
Metformin treatment improves glucose metabolism and reduces blood pressure in obese, nondiabetic, hypertensive women, leading to a more favorable cardiovascular risk profile.
RCT
Highly CitedThe effect of metformin on blood pressure, plasma cholesterol and triglycerides in type 2 diabetes mellitus: a systematic review
Metformin has a glucose-lowering independent effect on blood pressure and lipid profile in individuals with type 2 diabetes, potentially reducing macrovascular end-points and mortality.
Systematic ReviewHighly CitedEffect of Metformin on Blood Pressure
Metformin does not effectively lower blood pressure in non-diabetic individuals with mild hypertension, and does not affect insulin sensitivity.
RCTEffects of Vildagliptin and Metformin on Blood Pressure and Heart Rate Responses to Small Intestinal Glucose in Type 2 Diabetes
Vildagliptin reduces blood pressure and increases heart rate during intraduodenal glucose infusion in type 2 diabetes patients, while metformin increases heart rate without affecting blood pressure.
RCTVery Rigorous JournalEffect of metformin on blood pressure in patients with hypertension: a randomized clinical trial
Metformin did not reduce blood pressure, measured by ambulatory blood pressure monitoring, in hypertensive patients without diabetes.
RCTRigorous JournalMetformin reduces blood pressure and restores endothelial function in aorta of streptozotocin-induced diabetic rats.
Metformin treatment lowers blood pressure and restores endothelial function in streptozotocin-induced diabetic rats without significantly affecting blood glucose levels.
RCTAnimal StudyHighly Cited