Insulin Glargine

Primary Uses

Insulin glargine is prescribed to manage blood glucose levels in people with diabetes. It is a long-acting (basal) insulin that works slowly over about 24 hours to provide a steady level of insulin in the body.

Type 1 Diabetes

In people with type 1 diabetes, the body does not produce its own insulin. Insulin glargine is used in both adults and children to replace this missing hormone. It is typically used in combination with a fast-acting insulin injected before meals.

Type 2 Diabetes

In people with type 2 diabetes, the body either does not produce enough insulin or cannot use it effectively. Insulin glargine is used in adults to help maintain stable blood sugar levels throughout the day and night. It may be used alone or alongside other types of insulin or oral diabetes medications.

Important Considerations

• It is not used to treat diabetic ketoacidosis, which requires a fast-acting insulin treatment.
• It is meant for long-term management rather than immediate correction of high blood sugar spikes.

Mechanism of Action

Insulin glargine works by replacing the insulin that the body would normally produce. Insulin is a hormone that allows sugar (glucose) in the blood to enter cells, where it is used for energy.

This medication also helps manage blood sugar levels by:

• Helping muscle and fat tissues take up sugar from the blood.
• Preventing the liver from producing and releasing more sugar into the bloodstream.

Extended Release Profile

Insulin glargine is designed to be absorbed slowly after it is injected under the skin. Once it enters the fatty tissue, it forms tiny crystals that gradually dissolve and release the medicine into the bloodstream at a steady rate. This process allows the medication to work for a long duration, typically providing a consistent level of insulin for about 24 hours. Unlike some other types of insulin, it does not have a distinct peak in activity, which helps maintain stable blood sugar levels between meals and overnight.

Common Side Effects

The most common side effect of insulin glargine is hypoglycemia (low blood sugar). Other common side effects may include:

• Pain, redness, swelling, or itching at the injection site.
• Changes in skin feel or appearance at the injection site, such as thickening or small pits (lipodystrophy).
• Weight gain.
• Swelling of the hands and feet.
• Common cold symptoms, such as a runny nose or sore throat.

Serious Side Effects

Some side effects can be severe and require immediate medical care. These include:

• Severe low blood sugar: This can lead to dizziness, confusion, blurred vision, slurred speech, seizures, or loss of consciousness.
• Serious allergic reactions: Symptoms may include a rash over the whole body, trouble breathing, a fast heartbeat, sweating, or swelling of the face, lips, or throat.
• Low potassium levels (hypokalemia): This may cause muscle weakness, cramps, or an abnormal heart rhythm.
• Heart failure: When used with certain other diabetes medications called thiazolidinediones (TZDs), insulin glargine may increase the risk of heart failure. Symptoms include sudden weight gain, shortness of breath, or swelling in the ankles or feet.

Hypoglycemia

Low blood sugar (hypoglycemia) is the most common side effect of insulin therapy and can be life-threatening. The timing of hypoglycemia usually reflects the time-action profile of the insulin formulation. Changes in insulin regimen, meal patterns, or physical activity may increase the risk of low blood sugar.

Hypokalemia

All insulin products, including insulin glargine, cause a shift in potassium from the blood into the cells, which may lead to low potassium levels (hypokalemia). If left untreated, this can cause respiratory paralysis, heart rhythm problems, and death. Monitoring is particularly important for patients at risk, such as those using potassium-lowering medications.

Hypersensitivity Reactions

Severe, life-threatening, generalized allergy, including anaphylaxis, can occur with insulin products. If a serious reaction occurs, the medication should be discontinued immediately and medical treatment sought.

Medication Errors and Sharing

Insulin glargine pens or syringes must never be shared between patients, even if the needle is changed. Sharing poses a risk for transmission of blood-borne pathogens. Additionally, patients should always check the insulin label before injection to avoid accidental mix-ups between different types of insulin.

Fluid Retention and Heart Failure

When used in combination with thiazolidinediones (TZDs), insulin glargine may cause fluid retention and heart failure. Patients should be observed for signs such as shortness of breath, swelling of the ankles or feet, and sudden weight gain.

Renal and Hepatic Impairment

Patients with kidney or liver disease may require more frequent glucose monitoring and dose adjustments, as these conditions can change how the body processes insulin.

Pregnancy

Maintaining stable blood sugar levels is essential during pregnancy to reduce the risk of complications for both the parent and the developing baby. Insulin glargine is often used during pregnancy when insulin therapy is required to manage diabetes.

Available data from clinical studies and observational research have not identified a specific risk of major birth defects, miscarriage, or adverse outcomes associated with the use of insulin glargine during pregnancy. Because insulin requirements typically change throughout the course of pregnancy—often increasing during the second and third trimesters—frequent monitoring and dosage adjustments by a healthcare professional are necessary.

Breastfeeding

Insulin glargine is generally considered safe for use while breastfeeding. Insulin is a naturally occurring hormone in human milk, and any insulin glargine that passes into breast milk is likely to be broken down in the infant's digestive system rather than absorbed into their bloodstream.

Individuals who are breastfeeding may find that their insulin requirements change significantly compared to their needs before or during pregnancy. It is important to discuss blood sugar management and potential dosage adjustments with a healthcare provider during the postpartum period to ensure safety and effective glucose control.

Available Forms

Insulin glargine is a long-acting insulin provided as a clear, colorless solution for injection under the skin. It is available in the following delivery formats:

• Vials: Glass containers used with insulin syringes.
• Pre-filled Pens: Disposable, single-patient-use injector devices that contain a built-in reservoir of insulin.
• Cartridges: Units designed for use in specific reusable pen delivery systems.

This medication is intended for subcutaneous administration only and should not be used in insulin pumps or administered intravenously.

FDA Approval Status

Insulin glargine was first approved by the U.S. Food and Drug Administration (FDA) in 2000. It is indicated to improve glycemic control in both type 1 and type 2 diabetes mellitus. The approval covers:

• Adults with type 1 or type 2 diabetes.
• Pediatric patients with type 1 diabetes.

In addition to the original reference product, the FDA has approved follow-on biologics and biosimilar versions of insulin glargine. This includes the 2021 approval of the first interchangeable biosimilar insulin product, which allows for substitution at the pharmacy level under certain conditions.

Regulatory History and Safety Reviews

The FDA has conducted post-market safety reviews for insulin glargine. Between 2009 and 2011, the agency investigated a potential association between insulin glargine and an increased risk of cancer based on several published epidemiological studies. After a comprehensive review, the FDA concluded that the evidence did not show a clear link between the medication and cancer risk, and no changes to the clinical use of the drug were recommended.

Boxed Warnings and REMS

Insulin glargine does not have a boxed warning, and there is no Risk Evaluation and Mitigation Strategy (REMS) required for its distribution. Regulatory requirements focus on standard labeling to prevent medication errors, such as the risk of hypoglycemia and the prohibition of sharing insulin pens or needles between patients to prevent the transmission of bloodborne pathogens.

Factors Affecting Price

The price of insulin glargine is influenced by several factors, including the specific product version and how it is dispensed. Common factors include:

• Product Type: Insulin glargine is available as a reference brand and as several biosimilar or follow-on products. Biosimilars are highly similar to the original product and are often offered at a lower cost.
• Concentration and Delivery: This medication comes in different concentrations (such as U-100 or U-300) and delivery formats, including multi-dose vials and prefilled injection pens. The cost may differ between these options.
• Insurance Coverage: Most insurance plans include at least one version of insulin glargine on their formulary, but the preferred brand and the associated copay can vary significantly between plans.

Financial Assistance

Many manufacturers provide savings programs or patient assistance for those who meet specific eligibility requirements. Patients may also find price differences between various retail pharmacies.