Is Inhaled Insulin A Viable Alternative For Patients With Diabetes?

By Jennifer Pahira and John S. Steinberg, DPM

     According to the International Diabetes Federation (IDF), diabetes affects more than 230 million people worldwide and is expected to affect 350 million by 2025. Controlling blood glucose levels via subcutaneous injections of insulin has been a key clinical intervention for many people. While injected insulin has proven to be a reliable intervention, it is met with significant resistance by patients who want to avoid the stigma and pain associated with this therapy.

     Over the years, extensive research has been conducted in an effort to develop a less invasive and more patient-satisfactory means of insulin delivery. The approval of inhaled insulin could prove to be the first of many milestones in an attempt to make treatment delivery more acceptable to the patient.

     In January, the FDA approved Exubera (manufactured by Pfizer in collaboration with Nektar Therapeutics) for adults with type 1 or type 2 diabetes in both the United States and Europe. Exubera is short-acting inhaled insulin and can be absorbed faster than subcutaneous injection of insulin. The insulin comes in an inhaler weighing about 4 oz. It can be stored at room temperature and has a 24-month shelf life. The Exubera inhaler produces a cloud of insulin powder in a clear chamber visible to the patient. The insulin powder passes rapidly into the bloodstream to regulate the body’s blood sugar levels. Patients should take it before meals.1

     Historic difficulties in the development of an oral or inhaled insulin have included getting the insulin past the acidity of the stomach and digestive enzymes in the intestines, and opening the intestine for insulin transportation. Inhaling the insulin through the nose was ruled out because too much insulin was needed to pass through the mucus membranes. (In order to deliver 10 units into the blood, the patient must inhale 100 units.) Another detriment was the fact that enhancing transportation of the insulin with chemicals resulted in irritation of the nasal passages. This research concluded that inhaling the insulin directly into the lungs through the mouth would have the most potential.

     Inhale Therapeutic Systems has worked to create an insulin particle that would meet the needs of inhalation through the mouth. The particle developed is small enough to be inhaled and flow past the throat into the lungs but is large enough that the patient does not exhale the particles back into the air. One issue that is still under investigation is the precise control of how much insulin the patient is taking in. Precision is critical for all patients with diabetes. Therefore, long-acting insulin is still necessary for basal coverage of insulin requirements.

What The Research Reveals

     Although inhalation directly into the lungs seems to be a promising new clinical approach for insulin delivery, there are some concerns regarding the long-term effects of growth protein inhalation on the lungs.

     However, in a 2004 study conducted by Pfizer Global Research and Development, investigators noticed similar improvements in hemoglobin A1c levels and average changes in pulmonary function in separate patient groups taking inhaled or injected insulin. Overall, patients reported increased comfort and ease of use with inhaled insulin as compared to injection.

     Another study reported in the Archives of Internal Medicine confirmed similar results in people with type 2 diabetes who took either a combination of short-acting inhaled insulin and long-acting injected insulin, or took injected insulin alone. Researchers concluded that the addition of one to two pre-meal inhalation doses improved glycemic control without the need for additional subcutaneous injections.2

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