Implantable Pump Progress

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MiniMed Technologies’ implantable insulin pump (IIP) has shown to be an effective alternative to multiple dose injection (MDI) therapy.

Contrary to a previous study published in the August 1996 issue of Diabetes Care, the results reported from this study, sponsored by the U.S. Department of Veteran’s Affairs (VA), have been extremely positive. Dr. Christopher D. Saudek of Johns Hopkins University Medical Center and leader of both studies, reports, “This landmark study…is the first large-scale attempt to compare the effectiveness of the IIP to MDI. The pump proved to be successful in reducing the occurrence of hypoglycemia, eliminated weight gain and actually improved the quality of life for participating diabetic patients.”

Dr. Duckworth, co-leader of the study from the Omaha VA Medical Center, told DIABETES HEALTH that while IIP therapy is known to have positive effects on kidney and eye problems, this study was undertaken to see if “the method of (insulin) delivery has effects on future complications like cardiovascular problems in type 2 and I diabetics.”

High levels of insulin in the blood can cause cardiovascular problems. Dr. Duckworth explained that the insulin pump could remedy this problem by using less insulin in a more effective way, releasing small amounts as the body needs it rather than loading the body up with large amounts at one time as injections do.

The study, reported in the October issue of the Journal of the American Medical Association, showed the IIP offered several advantages over MDI. According to the study, the pump reduced the number of clinical insulin reactions by 68 percent and eliminated the weight gain that is commonly associated with MDI therapy. The test subjects on the pump lost an average of two or more pounds, compared to the MDI subjects who gained an average of 0.8 pounds. In addition the study claimed that IIP therapy also left patients reporting a far greater level of satisfaction and an improved sense of quality of life.

The difference between this study and the one published in the August 1996 issue of Diabetes Care, and reported in the November/December issue of DIABETES HEALTH, is the finding that the pump delivered insulin at a constant rate similar to that of a normal pancreas. By comparison, the report published in August claims that the MiniMed pumps suffered from a 74 percent underdelivery incidence rate.

Dr. Duckworth told DIABETES HEALTH that these problems were “entirely related to the insulin.” He explained that insulin has the natural tendency to aggregate in the blood stream and that every possible precaution needs to be taken in its preparation to prevent this from happening. Jerry Greg, president of MiniMed, told DIABETES HEALTH that Hoechst Marion Roussel, the producer of the insulin used in their pumps, has remedied the problem with “improvements to the system.” Dr. Duckworth explained these improvements as “a very minor change in the (insulin’s) preparation procedures.”

The studies also differed in whom they tested. According to Greg, the VA study was performed on people with type 2 diabetes (who are rarely prescribed with external pumps), and the study published in August was performed on type Is.

According to Dr. Duckworth the findings regarding insulin delivery would be the same for type Is and type 2s. He went on to explain that type 2s were studied because there were so few type Is in the VA system. He also agreed that a pump failure would be less dangerous for a type 2.

In the VA study patients all reported that they were “overjoyed” at the freedom the pumps provided. As Dr. Duckworth said, “…they (subjects in the test) could manage their diabetes without the disease controlling them.”

Also of interest is the use of VA facilities for studies such as this one. The VA has 173 medical centers across the nation under one administrative system. This puts them in an especially good position to evaluate large numbers of patients and produce scientifically valid results. There are currently almost 100 cooperative studies underway at VA medical centers involving more than 100,000 subjects.

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