Byetta & Pancreatitis was a subject that was brought up and mostly pursued by brokerage houses on Wall Street who were 'short' shares of AMLN. After studying the FACTS it is apparent that there is a LOWER indication of pancreantitis in Byetta users than in the overall diabetic or obese population.
The incidence rate of pancreantitis is actually LOWER in Byetta users. I am venturing a guess you were misinformed by a GP or uneducated endo.
According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) about 80,000 cases of acute pancreatitis occur in the United States each year. That is a rate of about one case per 3750 persons. Thirty cases of acute pancreatitis would be expected in the general population for every 112500 person years. The first question is, for how many person years has Byetta been used? Then based on that number, what would be the expected number of acute pancreatitis cases?
It might be possible to make an accurate estimate of Byetta person-year usage based on the total scrip data. Those data indicate that about 200,000 people were using Byetta as of January 1, 2006, and that about 450,000 people are now using it. That gives about 600,000 patient years of experience with Byetta since launch. Using the rate of acute pancreatitis in the general population, about 160 cases of pancreatitis would have been expected in a random sampling of this size.
However, pancreatitis is more prevalent among diabetics than the general population, and studies have also found that obesity increases the risk of pancreatitis by about ten percent for each 5 units of BMI, and also increased risk of other pancreas-related disorders (1,2,3). Considering the use pattern of Byetta, and its beneficial side effect weight loss along with the problem of obesity in diabetes, it is safe assume that a large factor in prescribing Byetta is weight loss, and that the average BMI of Byetta users is much higher than the target of 21-25. An average BMI of 35 would give a composite increased risk based on obesity alone of 20 percent, and about 192 cases of acute pancreatitis would have been expected. Diabetes itself also increases the risk of pancreatitis, so it is clear that a reported number of thirty during the period since Byetta launch is far below the expected levels and supports the notion that Byetta has an overall protective effect against pancreatitis among diabetics.
Adding to that is the fact that many other drugs contribute to pancreatitis risk, including many that are commonly prescribed for diabetes. According to a Swedish study (2) the use of glyburide (Micronase, a sulfonylurea drug) increase the risk of pancreatitis by two and a half fold. This effect was noted as early as 1975 with another sulfonylurea drug, tolbutamide (4). Since the initial approval for Byetta was for use in conjunction with metformin and/or sulfonylurea drugs it is certain that many Byetta users were using other drugs that increased their risk. Thus well over 200 cases of pancreatitis should have occurred among Byetta users so far.
Also in the FDA report is data that not all of the pancreatitis sufferers had a quick recovery, although most did. About 80 percent recovered without further intervention, which is about the overall recovery rate according to the NIDDK, so this does not point to any added risk of a poor prognosis. In addition, obesity is not just a risk factor of developing pancreatitis, but also in the severity of the disorder (5), and again with a prevalently obese cohort using Byetta the rate of recovery is not alarming.
Could Byetta be a contributing factor in some cases of pancreatitis? It is entirely possible, but the overall risk benefit analysis seems weighted in Byetta’s favor. The reported occurrence of pancreatitis was much lower in diabetics using Byetta than would have been expected considering just the added risk due to diabetes and obesity. Other drugs such as Orlistat (6), used to treat obesity, and Captopril (7), used to treat high blood pressure, for example, could also increase the risk in some persons. Only by a full understanding of all these potential contributing factors can Byetta be accurately assessed vis a vis pancreatitis. More needs to be known, yet at this stage it seems it is better to use Byetta than not to.
Finally, what could this mean for Byetta LAR? It is too early to tell how that program might be effected, but consider the only published case study of a person effected by pancreatitis while using Byetta (8). The patient developed symptoms of pancreatitis very soon after initiating Byetta treatment, and then was removed from all drug treatment, including other drugs that have a known effect of increasing pancreatitis risk. The case resolved itself quickly with no need for intervention. Although pancreatitis recurred after Byetta was reintroduced, the authors conclude that the other drugs cannot be ruled out as contributory. Thus, all that can be said is an association between Byetta use in this case and pancreatitis, not a cause and effect relationship. As for Byetta LAR, patients would likely not begin incretin therapy with the long acting version. It would be more prudent regardless of a potential pancreatitis issue to start with a low dose of Byetta, and titrate it to allow the patient to acclimate to the therapy. Only then would Byetta LAR be introduced, and by then it would be unlikely that an adverse event would occur.
Scott