(This article first appeared in the January/February 2005 edition of DIABETES HEALTH MONITOR. Reprinted with permission.)
Injected insulin was first used to treat diabetes in 1922. Since then, scientists
have learned much more about insulin's chemical structure. Their knowledge has
allowed them to tweak the insulin molecule and develop a variety of insulin
treatments, such as intermediate-acting preparations.
Now another milestone appears within reach: Inhaled insulin is undergoing clinical
studies that may lead to U.S. Food and Drug Administration (FDA) approval. This
option would benefit people with type 1 diabetes, who can't survive without
insulin therapy. It would also be a consideration for people who have type 2
diabetes, many of whom require insulin as the disease progresses.
Proof-of-concept studies
The road to FDA approval of a new medication -- or, in this case, a new delivery
system -- is a long one. But two recent "proof-of-concept" studies
have certainly helped inhaled insulin cover some distance by showing the product
can indeed improve blood glucose control in people with type 2 diabetes.
Insulin with diabetes pills.
The first study involved 68 adults with poorly-controlled type 2 diabetes. Their hemoglobin A1c levels (reflecting average blood glucose levels over the previous two to three months) ranged from 8.1% to 11.9%. The American Diabetes Association holds that an A1c of less than 7% represents adequate blood glucose control. All study participants had been taking oral diabetes pills -- a sulfonylurea drug such as DiaBeta (glyburide), Glucotrol (glipizide), or Amaryl (glymiperide), and/or Glucophage (metformin).
Why weren't pills alone sufficient? As type 2 diabetes progresses, the pancreas produces less and less insulin. Diabetes pills either rev up insulin production or increase insulin's ability to help glucose enter cells from the bloodstream. But the pills can't do their job if the insulin-producing cells can't do theirs.
The study participants were randomly assigned to use either the new dry-powder inhaled insulin plus their regular diabetes pills or their regular pills alone. Those in the insulin group (32 people) inhaled 1 milligram (mg) or 3 mg of insulin before their three daily meals. This was the equivalent of approximately three units and nine units, respectively, of inhaled regular insulin.
After 12 weeks, A1c Values fell by 2.3% in the inhaled-insulin-plus-pills group; in the pills-only group (36 people), values fell by just 0.1%. Moreover, 11 people in the insulin group (34%) saw their A1c level fall to 7% or lower. Nobody in the pills-only group achieved that level.
Injected insulin comparison.
Another 12-week study that was carried out in Europe compared inhaled insulin with injected insulin in 107 people with type 2 diabetes. Both forms of insulin were the fast-acting human type. The inhaled insulin was delivered by the AERx insulin diabetes management system, which is designed to send an aerosol (spray) of liquid insulin deep into the lungs.
Participants were randomly assigned to one or the other form of insulin. The inhaled-insulin group members took their doses just before meals, while the injected-insulin group members took theirs 30 minutes before meals. Doses were first based on the participants' previous insulin requirements and then adjusted, if necessary. Both groups of participants also injected NPH insulin in the evening.
At the study's end, A1c levels were approximately 7.8% in both groups. This demonstrated that inhaled insulin was as effective as the injected version.
Lung issues: None
Inhaled insulin enters the millions of tiny, thin-walled air sacs (alveoli) in the lungs. It can easily pass through the permeable walls of the alveoli into the bloodstream. There, it gets right to work on controlling the blood glucose.
Neither of the studies found any lung problems arising during the 12 weeks
from the use of inhaled insulin. Longer studies are now under way. And, a still-unpublished
two-year study compared inhaled insulin (Exubera) plus a diabetes pill with
a pill alone in 1,000 people with type 2 diabetes.