Metformin with Glucomannan Interaction Details

Brand Names Associated with Metformin

Medical Content Editor Dr. Brian Staiger, PharmD
Last updated Nov 05, 2023

Interaction Effect

Increased risk of hypoglycemia

Interaction Summary

High-fiber or fiber-supplemented diets are recommended to patients with diabetes mellitus to decrease postprandial hyperglycemia, hence guar gum, pectin, and glucomannan have found increased use. Glucomannan, an unabsorbable polysaccharide, has been shown to decrease glyburide plasma concentrations by 50% . Glucose concentrations were found to be decreased despite the reduced absorption of glyburide . Insulin and hypoglycemic agent dose requirements were reduced in patients taking glucomannan . Glucomannan may slow gastric emptying, increase the viscosity of gastrointestinal contents, and act as a barrier to diffusion, which slows absorption of hypoglycemic agents and glucose . Blood glucose should be monitored closely in patients taking glucomannan concomitantly with antidiabetic agents.

Severity

Moderate

Onset

Rapid

Evidence

Probable

How To Manage Interaction

Absorption of antidiabetic agents may be decreased by glucomannan, yet blood glucose concentration may still be decreased by glucomannan. If possible, separate administration of glucomannan and antidiabetic agents by several hours. Monitor blood glucose levels closely to ensure that glucose levels are adequately controlled.

Mechanism Of Interaction

Additive hypoglycemic effect

Literature Reports

A) Coadministration of glucomannan and glibenclamide (glyburide) decreased glibenclamide concentration in 9 healthy male volunteers aged 21 to 47 years. Glibenclamide 2.5 milligrams (mg) was administered on day 1 without glucomannan, followed by concomitant administration with glucomannan 3.9 grams on day 2. Plasma glibenclamide concentrations were reduced by approximately 50% when coadministered with glucomannan. Glibenclamide plasma concentrations with glucomannan versus control were 31.7 +/- 24.5 ng/mL versus 76.4 +/- 25.0 ng/mL at 30 minutes (p less than 0.002); 51.3 +/- 35.5 ng/mL versus 120.9 +/- 56.0 ng/mL at 60 minutes (p less than 0.02); 60.0 +/- 38.8 ng/mL versus 117.4 +/- 53.1 ng/mL at 90 minutes (p less than 0.05), and 54 +/- 31.5 ng/mL versus 100.7 +/- 46.5 ng/mL at 150 minutes (p less than 0.005). Interestingly, plasma glucose concentrations were lower at 30 minutes in those receiving glibenclamide with glucomannan than in those receiving glibenclamide with control .

B) In 13 patients with diabetes supplemented with 3.6 grams or 7.2 grams glucomannan (konjac mannan) for 90 days, mean fasting blood glucose was reduced by 29% (p less than 0.025). Dose requirements of insulin or hypoglycemic agents were reduced, and withdrawn in some patients .

Metformin Overview

• Metformin is used alone or with other medications, including insulin, to treat type 2 diabetes (condition in which the body does not use insulin normally and, therefore, cannot control the amount of sugar in the blood). Metformin is in a class of drugs called biguanides. Metformin helps to control the amount of glucose (sugar) in your blood. It decreases the amount of glucose you absorb from your food and the amount of glucose made by your liver. Metformin also increases your body's response to insulin, a natural substance that controls the amount of glucose in the blood. Metformin is not used to treat type 1 diabetes (condition in which the body does not produce insulin and therefore cannot control the amount of sugar in the blood).

• Over time, people who have diabetes and high blood sugar can develop serious or life-threatening complications, including heart disease, stroke, kidney problems, nerve damage, and eye problems. Taking medication(s), making lifestyle changes (e.g., diet, exercise, quitting smoking), and regularly checking your blood sugar may help to manage your diabetes and improve your health. This therapy may also decrease your chances of having a heart attack, stroke, or other diabetes-related complications such as kidney failure, nerve damage (numb, cold legs or feet; decreased sexual ability in men and women), eye problems, including changes or loss of vision, or gum disease. Your doctor and other healthcare providers will talk to you about the best way to manage your diabetes.

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Definitions

Severity Categories

Contraindicated

These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.

Major

This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.

Moderate

This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.

Minor

While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.

Onset

Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.

Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.

Evidence

Level of documentation of the interaction.

Established: The interaction is documented and substantiated in peer-reviewed medical literature.

Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.

How To Manage The Interaction

Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.

It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.

Mechanism Of Interaction

The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.

Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.

Where Does Our Information Come From?

Information for our drug interactions is compiled from several drug compendia, including:

• Gold Standard Drug Database
• Micromedex
• Lexicomp
• DrugBank

The prescribing information for each drug, as published on DailyMED, is also used. 

Individual drug-drug interaction detail pages contain references specific to that interaction. You can click on the reference number within brackets '[]' to see what reference was utilized.

The information posted is fact-checked by HelloPharmacist clinicians and reviewed quarterly.