Biguanides: Uses, common brands, and safety info

Biguanides are a class of antidiabetic medications, sometimes referred to as non-sulfonylureas, used to treat Type 2 diabetes. Type 2 diabetes is a condition where the blood glucose levels are elevated, sometimes called hyperglycemia. Having glucose levels in your blood is very important. Your pancreas releases insulin which then helps get the glucose to the cells where your body needs it for energy. With Type 2 diabetes, your body’s insulin doesn’t function as it should or you may not have enough. The result is that too much glucose is left in your bloodstream. Type 2 diabetes is significantly different from type 1 diabetes, a condition where your pancreas does not release insulin. Type 1 diabetes patients are considered insulin-dependent and must be treated with insulin.

There are several classes of antihyperglycemic medication that treat Type 2 diabetes with different approaches. These include various types of insulin, biguanides, sulfonylureas, alpha-glucosidase inhibitors, thiazolidinediones DPP4 inhibitors, SGLT2 inhibitors, and GLP-1 analogs among others. Here we will discuss the types, actions, and safety of biguanides.

Other biguanides (combination drugs):

• Invokamet

• Qternmet XR

• Segluromet

• Synjardy

• Synjardy XR

• Trijardy XR

• Xigduo XR

What are biguanides?

Biguanides are a first-line treatment for Type 2 diabetes. They are very effective at making an impact on blood glucose control and are generally cost-effective. While biguanides do not stimulate the pancreas to make more insulin, they do help the body utilize the insulin it has to the best of its ability. Biguanides also decrease the amount of glucose produced by the liver. 

All available biguanides in the U.S. contain the same active ingredient (metformin), but each available formulation has a unique release mechanism within the body. There have been other biguanides. Phenformin was removed from the market in the 1970s due to the severe incidence of lactic acidosis and its effects on the kidney and cardiovascular function. Buformin is the active ingredient of other biguanides available in foreign markets. Biguanides are just one of many types of medications with different medications for treating Type 2 diabetes. 

There is another type of biguanide, known as proguanil, which is used in treatment-resistant malaria. It is typically used with other medications to treat malaria, but it is not used to treat Type 2 diabetes. Alternatively, metformin is not used to treat malaria.

How do biguanides work?

Biguanides’ mechanism of action works in three ways to help your body lower your blood glucose over time.

Biguanides’ mechanism of action works in three ways to help your body lower your blood glucose over time.

1. Biguanides increase cell transport of glucose in peripheral tissues such as adipose tissue and skeletal muscle. This is thought to be due to the improved binding of insulin caused by the biguanides. The end result is better glucose uptake by cells.

2. Biguanides decrease hepatic gluconeogenesis, the production of glucose by the liver. The result is less glucose in the bloodstream. 

3. Biguanides decrease the absorption of glucose in the intestinal tract. While this action leads to some of the most common side effects of biguanides, it lowers the amount of glucose absorbed into the bloodstream from the intestinal tract.

What are biguanides used for?

• Type 2 Diabetes Mellitus

• Hyperinsulinemia secondary to polycystic ovarian syndrome (PCOS)**

• Prediabetes**

• Gestational diabetes**

• Drug-induced obesity**

• Early puberty and menses**

**indicates off-label use of the drug

Who can take biguanides?

Can men take biguanides?

Men can safely take biguanides. Renal function should be evaluated before the initiation of biguanide therapy as they are primarily eliminated by the kidneys. Biguanides should not be used in men who have Type 1 diabetes or metabolic acidosis.

Can women take biguanides?

Women can safely take biguanides. As with men, renal function should be evaluated before the initiation of biguanide therapy as they are primarily eliminated by the kidneys. Biguanides should not be used in women who have Type 1 diabetes or metabolic acidosis. Premenopausal women who have insulin resistance and are not ovulating may resume ovulation on biguanide therapy. Appropriate contraception should be considered in these cases.

Can you take biguanides while pregnant or breastfeeding?

Biguanides are not recommended for routine use during pregnancy. Metformin is known to pass through the placenta and expose the fetus to therapeutic concentrations of the drug. In gestational diabetic mothers, metformin is a second-line treatment. Insulin is always the preferred agent, but in mothers who can not or refuse to administer insulin, metformin is the second choice agent to control blood sugars during pregnancy.

Biguanides do cross into the breastmilk. However, clinical trials have shown no effects on growth, motor, and social development in early life. Hypoglycemia, or low blood sugar, is a possibility, and the risks should be carefully considered before administering metformin to a breastfeeding mother.

Can children take biguanides?

Biguanides are approved in certain pediatric populations for limited purposes. For the treatment of Type 2 diabetes, children 10 years of age and older can use immediate-release metformin or the metformin oral solution. Children should not use the extended-release formulations of metformin. In off-label use, metformin is sometimes used to delay puberty and early menses in girls as young as 6 years of age.

Can seniors take biguanides?

Seniors can take biguanides. Kidney and liver function should be monitored to determine the safety and any necessary dose adjustments. 

Are biguanides safe?

Recalls

• Viona Pharmaceuticals Inc., Voluntary recall of Metformin ER due to presence of NDMA, June 2021

• Nostrum Laboratories, Inc., Voluntary recall of Metformin due to presence of NDMA, January 2021

• Sun Pharmaceutical Industries, Inc., Voluntary recall of Riomet ER due to presence of NDMA, September 2021

Restrictions

You should not take biguanides if you have ever had a hypersensitivity reaction to biguanides or metformin.

Biguanides are contraindicated in patients with metabolic acidosis. Metabolic acidosis is a risk factor for lactic acidosis. This can lead to metformin accumulation in the bloodstream, a toxicity that can be fatal.

Kidney function should be screened prior to initiating therapy by obtaining the estimated glomerular filtration rate (eGFR). This should be repeated annually, and therapy in a patient with an eGFR of less than 45 should be monitored closely. If the eGFR is less than 30, biguanides should not be used. 

Gastrointestinal side effects such as nausea, vomiting, and diarrhea are common during the initial stages of treatment with biguanides. However, if the incidence of gastrointestinal side effects starts or increases well after being stabilized on metformin, the etiology should be evaluated. This could indicate a change in absorption status and could be a risk factor for lactic acidosis. 

The manufacturer recommends caution when using biguanides in patients with congestive heart failure. Other options to treat Type 2 diabetes may be preferred in this instance.

Metformin may result in decreased vitamin B12 absorption. Your healthcare provider may monitor your labs and make suggestions for supplements if the level gets too low. 

Treatment of diabetes with biguanides or other diabetes drugs does not negate the need for regular diabetes care and check-ups regarding your feet, eyes, and kidneys. Diabetes can have dangerous effects on other organs and these should be monitored closely.

Type 2 diabetics who have other medical conditions which cause delayed emptying of the stomach may not be the best candidates for biguanide therapy as these conditions alter glucose control and absorption.

All diabetes medications carry the risk of having a hypoglycemic event, where your blood sugar actually gets too low from using the medication. This commonly presents as feeling weak, shaky, and dizzy. Patients taking medications that lower blood sugar should keep emergency items that can be used to quickly bring their sugar back up. These include glucose tablets or an injection known as glucagon. The American Diabetes Association recommends that you and your loved ones and caregivers be familiar in advance with administering glucagon in emergencies.

Are biguanides controlled substances?

No, biguanides are not controlled substances.

Common biguanides side effects

Serious adverse events:

• Lactic acidosis

• Megaloblastic anemia

• Hepatotoxicity

Common reactions:

• Diarrhea

• Nausea

• Vomiting

• Flatulence

• Asthenia

• Indigestion

• Abdominal pain and discomfort

• Anorexia

• Headache

• Metallic taste

• Rash

• Ovulation induction

• Weight loss

How much do biguanides cost?

Biguanides are available generically and are generally very cost-effective. Biguanides have been on the market for quite some time, and many of the brand-name formulations are no longer made in the U.S., though their generic equivalents are still available. A one-month supply of generic, immediate-release medication is as low as $4 with a coupon available from SingleCare. Glucophage XR, and brand name formulation of extended-release metformin, is about $80 out-of-pocket for a one-month supply with no insurance coverage. With SingleCare, you can get this same prescription for $4 as well.

Your insurance may have restrictions in place as to which version of biguanides they will cover. Your pharmacist can help you determine how to get the best possible price. SingleCare is a great resource for information and savings on your prescriptions, saving you up to 80%. Be sure to check SingleCare’s website for your best price.