Overview of Currently Available Insulin Delivery Systems

Since the discovery of insulin in 1921 and the technological advancements of insulin therapy, the survival trajectory of individuals with diabetes has dramatically changed. Patients with Diabetes Mellitus 1 (DM1) and, as pancreatic beta cells progressively fail as seen in Diabetes Mellitus 2 (DM2), require insulin as an integral part of their pharmacological disease management regimen. In vivo, there are a multitude of processes that are designed to maintain euglycemia. Although an over-simplification of a complex, dynamic process, normal physiologic insulin secretion has both a basal (fasting state in which beta cells of the pancreas continuously secrete small amounts of insulin) and a bolus (post meal, larger amount of insulin secretion) mechanism. Understanding this balance is paramount to an insulin-dependent diabetic’s survival as both insufficient and excess insulin can have life-threatening implications. Exogenous insulin methods have been developed to mimic the physiological pattern of endogenous insulin secretion to maintain near-normal levels of glycemia. Although it has well-known health benefit outcomes for patients with diabetes, insulin injections were notoriously not easily accepted by patients due to discomfort, social stigma, and hypoglycemic risk (Tandon et al. Indian J Endocrinol Metab. 21(4):600–17, 2017). However, given the surge of advancements available on the market today, compliance has increased. Innovations in insulin delivery have allowed persons with insulin-dependent diabetes to choose from an array of treatment methods to find one that best suits them and their lifestyle. Insulin-dependent diabetes mellitus and preventing its long-term complications, such as retinopathy, nephropathy, and neuropathy, has been a driving force behind the innovations in insulin delivery systems (Nathan et al. N Engl J Med. 353(25):2643–53, 2005). The Diabetes Control and Complication Trial (Nathan et al. N Engl J Med. 329(14):977–86, 1993) and its long-term follow-up study, the Epidemiology of Diabetes Interventions and Complications Study (Epidemiology of Diabetes Interventions and Complications (EDIC) Research Group. Diabetes Care 22(1):99–111, 1999) have shown the positive effects of intense glycemic control on microvascular and macrovascular complications in diabetes. As outlined in the American Diabetes Association Standards of Care in Diabetes 2023, when choosing the type of insulin delivery for a patient, it is paramount that the regimen is individualized with the person’s specific needs, preferences, and skill level as integral parts of the decision-making process. In addition, it is important to ensure that the patient and/or caregiver undergo initial and ongoing education, training, and evaluation of techniques throughout the use of the insulin delivery system (El Sayed et al. Diabetes Care. 46(Suppl. 1):S111–27, 2023). In this section, we will explore the history of and currently available insulin delivery systems and understand the mechanisms in which they strive for good glycemic control with minimal hypoglycemia events to prevent diabetic complications and mimic physiologic insulin release.