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What is Insulin Lispro?
Insulin lispro is a fast-acting insulin analogue used to treat diabetes. It was one of the first insulin analogues developed as an alternative to regular human insulin for improved postprandial glycemic control.
Chemical Structure and Mechanism of Action
Like human insulin, insulin lispro is composed of 51 amino acids arranged in two chains – an A chain and a B chain – that are linked together by disulfide bonds. However, insulin lispro differs from human insulin in its amino acid sequence at positions 28 and 29 of the B chain. Specifically, the amino acids proline and lysine are reversed. This minor change results in insulin lispro having a faster absorption profile after subcutaneous injection compared to regular human insulin. Once injected, insulin lispro rapidly dissociates from the injected zinc complex and monomers quickly absorb into the circulation from the subcutaneous tissue.
Clinical Studies on Efficacy
Several randomized controlled trials have demonstrated insulin lispro’s efficacy in improving postprandial glycemic control compared to regular human insulin. In one such study involving 60 patients with type 1 diabetes, insulin lispro achieved a lower 2-hour postprandial blood glucose levels after a standardized meal compared to regular human insulin (165 mg/dL vs. 190 mg/dL). Hemoglobin A1c levels were also modestly but significantly lower with insulin lispro use over the 24-week study period. Additional studies corroborated these findings and also found insulin lispro to be well-tolerated with a safety profile similar to regular human insulin.
Dosing Considerations
Due to its rapid absorption profile, insulin lispro should be injected 15 minutes before or within 15 minutes after starting a meal. This timing closely mimics the body’s natural insulin response to food intake. In contrast, regular human insulin should be injected 30-45 minutes before eating. Insulin lispro’s more rapid onset of action also allows for more flexibility in meal planning compared to regular human insulin. As with other insulins, the dose needs to be individualized based on factors like the carbohydrate content, timing, and composition of meals as well as the individual’s glucose levels and insulin sensitivity. Self-monitoring of blood glucose is crucial to guide dosage adjustments.
Availability, Administration and Storage
Insulin lispro comes in a rapid-acting formulation available under the brand name Humalog. It is supplied as a clear solution in vials or pre-filled insulin pens for subcutaneous administration via injection. Similar to other insulins, it should be stored in the refrigerator between 36-46°F and protected from light once the bottle is opened. Unused insulin should be discarded after 28 days even if it still appears clear. Insulin lispro may also be mixed with insulin lispro protamine suspension for a longer-acting effect when taken as part of a basal-bolus regimen.
Special Considerations in Patients with Diabetes
Insulin lispro offers an option for patients looking for an ultra-rapid acting insulin that more closely mimics the body’s normal physiological response to meals. While it does provide modestly better postprandial glucose control versus regular human insulin, strict attention to injection timing, meal consistency, and ongoing glucose monitoring is still required to minimize hyper- and hypoglycemia risks. Injection site rotation is also recommended to prevent lipohypertrophy from frequent injections. As with any insulin therapy, patients should receive nutrition and diabetes education to properly incorporate insulin lispro into their overall self-management. With appropriate guidance, insulin lispro has become a valuable tool for optimizing glycemic control in both type 1 and 2 diabetes.
Conclusion
In summary, insulin lispro was one of the earliest insulin analogues developed as an improvement over regular human insulin. Its chemical modification results in a faster absorption profile that more closely mirrors the body’s innate insulin release in response to meals. Well-designed clinical studies have confirmed insulin lispro’s modest benefits in postprandial glucose control compared to regular human insulin. Over two decades of clinical experience has proven insulin lispro to be a generally well-tolerated and effective treatment option for prandial glycemic management. With adherence to principles of flexible dosing, timing, self-monitoring and education, insulin lispro can help diabetes patients achieve their individualized glycemic targets.
