Insulin Interchanges and Formulary Considerations

Background

According to the Centers for Disease Control and Prevention (CDC), 30.3 million Americans, 9.4% of the U.S. population, are living with diabetes.1 The total direct and indirect costs associated with diagnosed diabetes in the U.S. in 2012 were $245 billion, according to the American Diabetes Association (ADA).2 Direct medical costs were estimated to be $176 billion, with prescription medications, including insulin, and diabetes supplies accounting for 18% and 12%, respectively, of the direct medical costs.2

These economic realities are increasingly complicating the ultimate goal of health systems: delivering excellent and individualized patient care. Health-care professionals now have more choices than ever available to formulate a patient-specific insulin regimen. They are tasked with designing a regimen that satisfies the patient, provider and payor.

From an outpatient perspective, providers theoretically have all insulin options available for them to prescribe. Prescribers must consider the many variations in prescription benefits, including high deductibles, out-of-pocket maximums, gaps in prescription coverage and changes in prescription formularies.

Conversely, inpatient considerations are driven by the cost of a medication and contractual agreement to purchase the medication from a wholesaler. Patients admitted to the hospital may be on a variety of diabetes medications as an outpatient, including insulin U-100, other concentrated insulin, mixed insulin combinations, or fixed-dose-combination medications such as glucagon-like peptide 1 (GLP-1) agonist/basal insulin. This presents a challenge to health-care professionals in a hospital setting, who are restricted to a limited insulin formulary. Inpatient providers may have limited knowledge of or experience with new insulin products, and there is often a lack of definitive reference material to aid the prescriber to make a conversion. Even when definitive product conversion is available, it may be further confounded by changing caloric intake and physiologic stress response during an acute illness.

In acknowledgment of the above realities, our institution decided to create an insulin interchange document for our health system. This Pharmacy and Therapeutics Committee-approved document compares all possible insulin products a patient may utilize prior to hospital admission, insulin conversions, as well as dosing considerations when making an insulin change. This is not a static document and is subject to constant revision as new products become available, hospital formulary changes and additional clinical guidance becomes available.

Insulin Interchanges and Formulary Considerations Table 2

Our document separates all available insulin products on the U.S. market into categories based on onset of action. Tables 1 and 2 reference the available products and indications. There are recommendations and comments associated with each conversion that are based on information found in the package inserts of the products as well as a review of current literature.3-13 Table 3 includes conversion information from a non-formulary product to a formulary product and the complementary conversion as well. These additional conversion recommendations help to make this document useful to other institutions and help to keep the document relevant in the future as the formulary at our own institution is updated.

Insulin Interchanges and Formulary Considerations Table 3 Part 1

Insulin Interchanges and Formulary Considerations Table 3 Part 2

Types of insulin

There are many formulations of insulins available in the U.S. market. Typical outpatient regimens consist of basal insulin, basal/bolus insulin with and without a correction scale, or a fixed-dose basal insulin/GLP-1 agonist.

Insulin conversion

When converting insulins, the goal of the patient care team is to find the insulin and dosage regimen that best helps the patient obtain or maintain euglycemia. Patient and clinical factors that affect the ability to maintain euglycemia include patient’s dietary intake, anticipated surgeries or procedures during the hospital stay, physiologic response to stress and medication-induced hyperglycemia. The following insulin conversion examples are recommendations based solely on identifying an appropriate dose to maintain euglycemia in an otherwise healthy individual. Additional dose adjustments may be necessary.

Conclusion

Insulin regimens and insulin dosing are becoming increasingly complicated as new products become available, new trial data are released related to existing insulin products, and institutional and insurance formularies change. When delivering care to patients with diabetes, there is never one perfect solution applicable to all patients. Health-care professionals can use their time more efficiently when the information they need in order to provide excellent patient care is accessible and concise. This document may assist health-care providers to balance therapeutic needs with economic realities to deliver sustainable and high-quality care.

Access additional resources and practical information to enhance the care and treatment of your diabetes patients.

Joshua GaborcikAbout our experts: Mark Albright,
PharmD candidate 2019, The Ohio State University College of Pharmacy

Joshua W. Gaborcik, PharmD, BCPS, specialty practice pharmacist–Internal Medicine, The Ohio State University Wexner Medical Center

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