Diabetics who inject themselves with insulin several times a day are eager for news about inhaled insulin, which has been in clinical trials in the United States for several years. They’ll be glad to hear that inhaling insulin, rather than injecting it, may not be too far in the future.
The results of several studies were presented at the scientific sessions of the American Diabetes Association in San Antonio, Texas. Several reported on the bioavailability of inhaled insulin — how quickly it becomes available for the body to use — and several more reported on effectiveness and patient satisfaction when used by those with type 1 and type 2 diabetes.
More than one device has been developed, but basically, the inhalers work like asthma inhalers. In one system, dry insulin powder is put into the device and breathed into the lungs, where it quickly enters the blood stream. In another, liquid insulin is used in the inhaler.
An international group of researchers led by Tim Heise and Klaus Rave, both of Mainz, Germany, presented findings from their studies with healthy volunteers. Each of 12 subjects received insulin three ways: using the inhaler with powdered insulin, using a normal injection method, and intravenously. The researchers report that inhaled insulin, as expected, showed a faster onset of action than regular insulin, and took about the same time to peak in the blood as intravenous insulin.
These researchers also reported that the action of inhaled insulin is dose-dependent — that is, when subjects inhaled larger amounts of insulin, measurements of insulin in their blood showed corresponding increases.
Another group of researchers led by Robert Fishman of Sunnyvale, California, tested a liquid insulin inhaler with 12 healthy volunteers, comparing this to injection. They also report that the inhaled insulin was absorbed more quickly than when injected under the skin.
These findings came from studying inhaled insulin in healthy participants, but researchers also presented findings from the clinical trials that have been using inhaled insulin to actually treat diabetes.
A group of researchers led by Joseph Cappelleri and Robert Gerber of Groton, Connecticut, reported that when 56 adult patients with type 2 diabetes were randomized to receive either inhaled insulin or insulin injections for 12 weeks, both groups maintained blood glucose control. But on a measure of patient satisfaction, the patients using the inhaler scored much higher. In particular, they found the inhaler easier to use, more comfortable, and more convenient than injections.
This same group also reported on 70 patients with type 1 diabetes. At the end of their 12 week clinical trial, in which half had taken inhaled insulin and half injections, the patients were offered the opportunity to continue therapy with either method for another year. Eighty one percent of those in the inhaler group and 79 percent of those in the injection group, chose to use the inhaler for the year. These patients reported significantly greater satisfaction with their treatment than the patients that chose to use injections for the year. In addition, those from the original inhaler group who chose to switch back to injections tended to have lower satisfaction scores after they made the switch. Patients from the injection group who switched to the inhalers, on the other hand, had significantly higher satisfaction scores after the switch. Again, all of the patients were able to maintain good blood sugar control.
“These data suggest that [inhaled insulin] is preferred over [injected insulin] and results in better patient satisfaction… not only in the short-term, but also during long-term treatment to at least one year. Improved satisfaction may, in clinical practice, increase willingness of patients to initiate and comply with insulin therapy and hence achieve better glycemic control,” the researchers concluded.
Another report, presented by William Cafalu of Burlington, Vermont, also said that inhaled insulin appears to be both safe and effective over the long term as well as for short periods. Again, patients with type 1 or type 2 diabetes who had completed any one of three 12-week clinical trials were offered the chance to use the inhaler for two years. These patients had good blood sugar control and normal lung function over this longer period.
“These results suggest that the clinical efficacy and pulmonary safety of [inhaled insulin], shown previously in short-term trials, are sustained long-term,” the researchers concluded.
Overall, the research presented at the ADA sessions suggests that inhaled insulin is both safe and effective, allowing those with either type 1 or type 2 diabetes to control their blood sugar without causing any lung problems.
Because it’s faster-acting than injections, researchers suggest that it will be particularly helpful for those who take insulin just before eating — they won’t have to wait as long, and it’s much more convenient, especially in public.
Inhaled insulin is still in clinical trials, but if its safety and effectiveness continue to be shown in future studies, patients with diabetes can look forward to a much easier way to take their insulin in the future.
Editorial Commentary: The goal of treating diabetes, whether type 1 or type 2, is to maintain normal blood glucose levels over time. For many this means giving insulin injections. Although giving injections is relatively painless with shorter, smaller needles, many patients still dislike performing this task. Inhaled insulin has been developed as a means to avoid insulin injections while still providing adequate amounts of insulin for the body to use. In the clinical trials that have been performed thus far, inhaled insulin appears to be effective and well accepted by patients. Many prefer it to injections. I look forward to using this technology in my patients when it becomes available. However, there are several caveats. First, patients must still test their blood sugar levels to monitor their diabetic control. For many, the task of pricking their fingers is far more painful than giving insulin injections. Second, this is a new treatment and with any new medication there are potential risks. Doses of insulin that are inhaled into the lungs are far greater than those given by injection. Although we have data on small numbers of patients followed for up to two years, it is unknown what the effect of insulin on lung tissue will be after 5 or 10 years of use. Therefore, it will be important to follow patients over time on inhaled insulin to be sure that their lung function remains consistently normal. Third, inhaled insulin is relatively short acting, so an injection or two of longer acting insulin may still need to be given. With these considerations in mind, for some patients, inhaled insulin will provide a welcome relief from the need to give daytime insulin injections.