Insulin in the Treatment of Diabetes Mellitus

Exogenous insulin is used in the treatment of diabetes, primarily type 1, to supplement deficient insulin creation in pancreatic beta cells. Exogenous insulin is injected and acts similarly to its endogenous counterpart, helping to normalize glucose levels and metabolism. Insulin works mechanistically by activating glucose transporters in the cell membrane to cause uptake of glucose into the cell. Most commonly, insulin is injected subcutaneously with a syringe or through a pump that allows automation of insulin injection. This allows the medication to bypass the digestive system as it can interfere with insulin delivery. Still however, there are other factors to be considered in drug delivery. Increases in temperature, exercise, and local massage can increase absorption, while decreased temperature and lipohypertrophy can decrease absorption.[1]

With insulin therapy, the goal is to mimic the endogenous release of insulin. Different preparations of biosynthetic insulin are available to do so, and are classified by their onset, peak and duration.  Rapid-acting insulins, such as Lispro, Aspart, and Glulisine, are quickly absorbed, with a faster onset and higher peak[1]. They are administered before or after meals to account for the high influx of glucose, to mimic endogenous insulin[2][3][4]. Intermediate and long-acting insulins, such as insulin Zinc, Isophane and Glargine, are absorbed slower, with a prolonged onset and lower peak[1]. They are advantageous in maintaining a constant background level of insulin throughout the day or night, and in between meals[5]. Mixtures of various types can also be tailored for specific cases to optimize glycemic control and minimize injections[1]. Dosage is not uniform when being prescribed and is highly variable to individual requirements. Once injected, insulin is absorbed rapidly and is metabolized by the liver, spleen, kidneys and muscles[6].

Therapists should be of aware of the adverse effects that patients might experience to provide increased quality of care. Hypoglycemia, or low blood sugar, can occur with missing meals, intense exercise, or an excessive dose of insulin. The patient will present with extreme hunger, fatigue, irritability, cold sweats, trembling hands, intense anxiety, and confusion. Diabetic ketoacidosis can occur with non-intake of insulin. The patient will exhibit polyuria, nausea, vomiting, and abdominal pain. This is a medical emergency as it can lead to shock, coma, or death[7]. If an insulin pump is being used, it needs to be closely monitored to ensure it is working properly as improper amounts of insulin administration can lead to the aforementioned side effects. With repeated injections, there is a possibility of injection site irritation or hypersensitivity[7]. Physical Therapists must be familiar with possible symptoms as to monitor for signs of adverse effects.

Polypharmacy needs to be observed as well. Insulin can have drug interactions with other prescription drugs that can impact insulin’s effectiveness. Beta blockers, Clonidine and Reserpine can hide signs of hypoglycemia. Corticosteroids, thyroid supplements and estrogens increase the needs for therapy. Alcohol, MAO inhibitors, and ACE inhibitors decrease the need for insulin. Glucosamine can also make blood glucose control more difficult[6].

Vials should be refrigerated and the patient should inspect the bottle for any changes in the serum as well as checking the expiration date before use as that can decrease drug potency. Patients should consider keeping a spare vial of insulin with them in case of emergency.[8]

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References

  1. 1.0 1.1 1.2 1.3 Donner, T. (2015). Insulin–pharmacology, therapeutic regimens and principles of intensive insulin therapy.
  2. Cox SL. Insulin glulisine. Drugs Today. 2005;41:433–440.
  3. Oiknine R, Bernbaum M, Mooradian AD. A critical appraisal of the role of insulin analogues in the management of diabetes mellitus. Drugs. 2005;65:325–340.
  4. Vazquez-Carrera M, Silvestre JS. Insulin analogues in the management of diabetes. Methods Find Exp Clin Pharmacol. 2004;26:445–461.
  5. Davis SN. Insulin, oral hypoglycemic agents, and the pharmacology of the endocrine pancreas. In: Brunton LL, et Al, eds. The Pharmacological Basis of Therapeutics. 11th ed. New York: McGraw-Hill; 2006.
  6. 6.0 6.1 Ciccone, C. D. (2013). Davis's Drug Guide for Rehabilitation Professionals. Philadelphia: F.A. Davis Company.
  7. 7.0 7.1 Alotaibi, A., Al Sultan, B., Buzeid, R., Almutairi, M., Alghamdi, E., Aldhaeefi, M., & Albareqi, M. (2018). An overview of insulin therapy in pharmacotherapy of diabetes mellitus type I. International Journal Of Community Medicine And Public Health, 5(3), 834-838.
  8. American Diabetes Association. (2003). Insulin administration. Diabetes care, 26(suppl 1), s121-s124.