The Future of Inhaled Insulin Therapy

Diabetes is a destructive disease that kills thousands each
year in the United States and disables thousands more, and its incidence has
been rising dramatically. Glycemic control is imperative to forestall
complications; however, it can be difficult for patients to achieve glycemic
goals. Many persons with diabetes will require insulin therapy to obtain
glycemic goals. Clinicians and patients are sometimes apprehensive about
starting insulin therapy for various reasons. Several inhaled insulin products
are in development, including the AIR and Technosphere Insulin systems, although
one product (Exubera) was recently removed from the market because of
disappointing sales and the development of another product (AERx) was recently
discontinued. Inhaled insulin may be an alternative therapy and because of added
convenience may improve patient adherence. (Drug Benefit Trends. 2008;20:63-70)

 

Diabetes is a leading cause of blindness, end-stage renal disease, neuropathies, and peripheral vascular disease, which can result in amputation. Persons with diabetes have as high a risk of a cardiovascular event as persons without diabetes who have had such an event.^1,2 In addition to being the sixth leading cause of death in the United States, diabetes is a national epidemic: approximately 16 million US persons have received a diagnosis of diabetes, and an additional 6 million US persons are believed to have undiagnosed diabetes.³

Tight glycemic control is imperative to reduce the risk of complications associated with type 1 and type 2 diabetes.^4-7 The American Diabetes Association recommends a glycosylated hemoglobin (A_1C) level below 7% minimally, and as close to 6% as possible if this level can be achieved without significant adverse effects.⁸ Glycemic control reduces the risk of microvascular disease (retinopathy, neuropathy, nephropathy) and shows a trend to reduce the risk of macrovascular events.⁹ However, glycemic control is difficult to achieve, as evidenced in clinical trials^4-6 and in clinical practice.^10,11 Insulin therapy is required to meet these goals in many patients, but multiple daily injections of insulin are perceived adversely by patients and clinicians alike.^12,13

Insulin is a polypeptide that is denatured in the GI tract when taken orally; therefore, intravenous or subcutaneous administration is necessary. Patients are required to receive multiple doses of insulin parenterally. Since the advent of insulin therapy, alternative delivery routes and systems have been investigated. Pulmonary delivery is ideal because insulin can diffuse into the bloodstream at the level of the alveoli.

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