Problems associated with human insulin are rare
Pure pork insulin still is available
For decades, diabetics who needed insulin had several options open to them, among them mixed-beef and pork-based insulin.
Since manufacturers stopped making the mixed insulin in the United States about a year ago and stockpiles are now nearly completely depleted, there have been some reports that patients switching to human insulin have difficulty in maintaining glycemic control. Some of those patients say they have experienced hypoglycemic unawareness: occasions when they are unable to recognize when their low blood sugars may be causing cognitive impairment.
However, pure pork insulin is still available for those who feel they cannot tolerate the human-based insulin. One news report in the Journal of the American Medical Association earlier this year chronicled the story of a man who had used beef/pork-based insulin for 32 years and when he switched to human-based insulin, suffered what he called episodes of extreme hypoglycemic unawareness.
However, some experts in the field downplay those reports. "Hypoglycemic unawareness was first reported in 1923, shortly after the discovery of insulin," says John Holcombe, MD, senior clinical research physician for Eli Lilly and Co. in Indianapolis. "It has to do with the duration of the disease, usually for Type 1 diabetics, not the type of insulin that is used. Ask patients, Is there’s a difference in unawareness?’ and they say, Yes.’ But switch them to a blinded trial, and they can’t tell the difference," says Holcombe.
He notes that the U.S. Food and Drug Admini-stration has looked into the issue of hypoglycemic unawareness as far back as 1991, and the advisory committee said there was no difference in the incidence of such problems with the varying types of insulin.
In fact, Holcombe points out, human-based insulin is now the world standard and offers the benefit of less-frequent allergic reactions and avoidance of tissue changes at the site of injection.
He adds that many patients on insulin continue to purchase their insulin for years without seeing a doctor and may only now become aware they can no longer obtain the medicine they have used for decades — with some resulting apprehension. Many patients received standing prescriptions years ago and, unless the doctor designates a specific number of refills, there is no particular requirement for them to see a physician in order to keep getting insulin. Most recently diagnosed patients are much more closely monitored, but Holcombe theorizes that some long-time diabetics who are unable to find animal-based insulins may not have seen a doctor for their diabetes in years.
Many endocrinologists agree that human-based insulin has been beneficial to their patients, but warn that human insulin works faster than animal-based insulin, and its time of action may be shorter, so patients may need to monitor more frequently.
"My general feeling is that hypoglycemic un-awareness is not a problem with my patients," says John Miles, MD, an endocrinologist practicing at St. Luke’s Hospital and a professor of med-icine at the University of Missouri in Kansas City. He suggests that some patients are resistant to change, and now with the dwindling availability of animal-based insulin, some many be feeling insecure. "I don’t think patients should lose sleep over this. I consider the human-based insulins as great progress."
Hundreds of patients Miles has treated have made the switch easily, and "people aren’t telling us they have a problem," he says. A few patients have reported a mild skin reaction at the injection site, which seems to disappear after a couple of weeks, he adds.
The two U.S. manufacturers of insulin, Eli Lilly and Co. of Indianapolis and Novo Nordisk of New York City, still produce pure pork insulin, but both companies say the more than 98% of their market is for human insulin.
Novo spokeswoman Susan Jackson says the company intends to continue producing the pork-based insulin "as long as there is a real need for it."
While virtually all new diabetic patients are placed on human insulin, Holcombe says animal-based insulins may be necessary for small numbers of patients who have allergic reactions to human insulins. Eli Lilly issued a similar statement.
Both companies have phased out their animal-based insulins from the market in the 15 years since human insulin became widely available. But they say that recombinant human insulin, which is virtually identical to the natural insulin produced by the human body, is a far superior therapy.
Many diabetics have found particular comfort in the introduction of lispro insulin. Because of the chemical reversal of the positions of two amino acids in the human insulin molecule, lispro mimics the body’s natural rapid insulin output after a meal more closely and allows a person with diabetes to inject insulin immediately before beginning to eat.
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