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Inhaled Insulin Seems Safe, Effective

Kate Traynor

Two new studies show that people with diabetes may be able to substitute large doses of inhaled insulin for small injections, at least before meals.

Patients with type 1 or type 2 diabetes inhaled a dry-powder insulin product before meals but used an injection of long-acting insulin at bedtime. Inhalation of insulin did not interfere with the study participants’ lung function, and none of the patients who used the inhaled insulin had a serious adverse event.

Serum levels of hemoglobin A1C decreased in response to inhaled insulin during the two studies, indicating that control of a patient's glucose level improved with treatment. This control was achieved with a high dosage of inhaled insulin—about 12 to 15 mg/day.

These findings come from two 12-week studies conducted by a single research group. One study, which was reported in the Feb. 3 issue of Lancet, presented findings from a randomized trial comparing the ability of inhaled and injectable forms of insulin to control blood glucose levels in patients with type 1 diabetes. The other report, published in the Feb. 6 Annals of Internal Medicine, described an uncontrolled trial of the safety and efficacy of inhaled insulin in adults with type 2 diabetes.

Thirty-five patients in the type 1 diabetes study and all 26 adults who enrolled in the type 2 diabetes study inhaled dry-powder insulin before eating each meal. Each study participant who used inhaled insulin also self-administered a single subcutaneous dose of ultralente insulin at bedtime.

There was no control group for the type 2 diabetes study. The type 1 diabetes study included a control group of 37 patients who injected themselves with a subcutaneous dose of insulin two or three times each day. One patient in the control group found compliance with required clinic visits difficult and withdrew from the study.

Dry-powder recombinant insulin was provided as blister packs containing 1 or 3 mg of the drug. Patients used a hand-held device to deliver insulin doses in one or two inhalations. According to the researchers, the lungs absorb about 3 units of insulin for each milligram of drug inhaled. All study participants adjusted their insulin dosages to maintain a blood glucose level of 100 to 160 mg/dL.

Despite the absence of serious adverse events, 94 percent of the people with type 1 diabetes who used inhaled insulin had at least one hypoglycemic episode during the study. Eighty-four percent of the patients in the control group had one or more episodes of hypoglycemia. The percentage of type 1 diabetes patients who had at least one severe episode of hypoglycemia, 14 percent, was the same in the inhaled and injected insulin groups.

In the type 2 diabetes study, none of the patients who used inhaled insulin had a severe episode of hypoglycemia during the trial, though 69 percent had one or more episodes of mild or moderate hypoglycemia. The lack of a control group prevented the researchers from comparing the frequency of hypoglycemic attacks between users of inhaled insulin and people who controlled their type 2 diabetes with insulin injections or other methods.

The adults who completed the type 1 diabetes study were, on average, 35 to 40 years old and had a body mass index of 24–26 kg per square meter. Patients who participated in the type 2 diabetes study were 51 years old on average and had an average body mass index of 30–33 kg per square meter. Only patients whose blood sugar was controlled by two or three daily insulin injections were eligible for either study. Except for having a diagnosis of diabetes, all study participants were in good overall health.

Funding for both studies was provided by Pfizer Inc., manufacturer of the dry-powder recombinant insulin.