Human vs. Beef/Pork Insulin

The following is an adaptation of a position statement that originally appeared in the June 1995 edition of Canadian Diabetes, a publication of the Canadian Diabetes Association's Clinical & Scientific Section. The findings of the "Quebec Committee" that studied the questions surrounding the discontinuation of a brand of beef/pork insulin are presented below. Your questions and comments are welcome.

What place does beef/pork insulin have in treating diabetes? And what happens when people switch from animal to human insulins?

Those were two of the questions raised in early 1995, when Novo Nordisk Canada Inc. decided to stop producing beef/pork insulin, effective June 30, l995. The only other Canadian company making beef/pork insulin, Eli Lilly Canada Inc., announced it would continue to do so, at least until 1999.

The Association of Endocrinologists of Quebec, in cooperation with the Order of Pharmacists of Quebec, responded to this news by forming an ad hoc committee. Its role: to evaluate the place of beef/pork insulin, and to make recommendations for the best ways of transferring from one type of insulin to another.

One quarter use animal insulin

According to estimates provided by the insulin-making companies, about 24 percent of diabetes patients across Canada use animal insulins. That ranges from 18 percent in Quebec to 30 percent in New Brunswick/Prince Edward Island.

In the way their molecules are structured, human insulin differs from pork insulin by a single amino acid, and from beef insulin by three amino acids. What does that mean? For one, it means that human insulin dissolves in water more easily than pork insulin and gives rise to less antibodies than beef insulin. Here are some other ways the properties of each type of insulin influence how they're handled in the body:

  1. Human insulin is absorbed quickly, and is active for a shorter period.

  2. The presence of insulin antibodies could slow the action of animal insulins, especially beef.

Since highly purified animal and human insulins have come on the market, certain problems have all but disappeared (such as allergies, the loss of fatty tissue where injections occur, and resistance to the effects of insulin). Less than five percent of people who use insulin suffer these problems.

Pros and cons

Overall, changing to human insulin means little difference in controlling diabetes, though some patients who have poor control using animal insulin may benefit.

Switching from animal to human insulin often means only small changes in the dosage. About 15 percent of the people who switch, however, may require significant dosage adjustments.

Compared to animal insulin, human NPH insulin (an intermediate-acting insulin preparation) has a shorter action period. Therefore, patients who had required just a single morning injection using animal insulin may need a second NPH injection later in the day.

Patients who were previously on NPH twice a day may also have to shift their injection from supper to bedtime. This avoids low blood sugar at night and high blood sugar in the morning.

For the same reason, injections of long-acting forms of human insulin (Ultralente) may have to move from the morning to the evening.

One advantage of human insulin over animal insulin is its availability in cartridges for use in pen injectors. That simplifies treatment for people who must have several injections, and may be much easier for older patients or those with sight problems.

The main complication of insulin treatment is low blood sugar (hypoglycemia). Recognizing the signs early is the best defense against any impact on the nervous system or comas. Some 30 percent of patients on insulin will have at least one hypoglycemic coma in their lifetime, and three percent will have recurring comas. As well, 10 percent will have a severe hypoglycemic reaction each year.

Does low blood sugar increase after switching to human insulin? That controversy hasn't been resolved. Most studies don't show any difference in the frequency, impact, or awareness of low blood sugar between people on animal and human insulin. Any reported differences are small, and their meaning is questionable. The introduction of human insulin also hasn't increased the incidence of sudden death in people with diabetes under age 50.

Overall, then, there doesn't seem to be a case that low blood sugar is any worse for patients on human insulin. Anecdotes and observations from doctors show that on animal insulin some patients, better controlled, can recognize on their low blood sugar more easily, or feel more confident about their treatment. It is recommended by some that more studies are needed on this subject and that animal insulins should remain available until further studies are completed.

The bottom line:

After reviewing the evidence, the ad hoc committee came up with a list of recommendations and a protocol for switching insulins, which the Association du Diabete du Quebec and the Canadian Diabetes Association's Clinical & Scientific Section endorsed.

The key recommendations include:

Patients who can control their diabetes well with beef/pork insulin should continue on it. Sometimes, switching to human insulin means increased injections. If patients are under control with beef/pork insulin and don't want more injections, that's another reason for staying with animal insulin.

Patients who believe they can feel low blood sugar better on animal insulin can try returning to it.

The small percentage of patients on animal insulin who have the problems mentioned earlier (allergies, losing fatty tissue at injection sites, resistance to insulin's effects) should switch to human insulin.

In cases where insulin is needed only intermittently, human insulin is better.

Who can decide on changing the type of insulin? That should be left to the endocrinologist or the treating physician. Except in emergencies, pharmacists are not authorized to exchange human insulins for beef/pork insulins. Unless their reasons are justified, medical professionals also shouldn't pressure patients to switch from animal to human insulins.

With that in mind, the ad hoc committee suggested that when switching insulins:

  1. All transfers should be medically supervised.

  2. Patients must receive detailed information about how the change will occur.

  3. To effectively adjust the doses of insulin, patients must temporarily do more self blood sugar testing more often. If not, closer medical follow-up is required.

  4. Patients who were previously on animal insulin should lower the initial dose of human insulin by 10 to 20 percent.

  5. Patients can use the same dosage schedule if switching from Novo Nordisk's animal insulin to Eli Lilly's animal brand of insulin.

Adapted from the Report of the Ad Hoc Committee on Beef-Pork Insulins by Nahla Aris-Jilwan MD, Pierre Malheux MD, Tina Kader MD, Alain Boisvert B.Pharm, DPH, MSc, and Sara Meltzer MD. Adapted by Stuart Foxman

This page was added on June 6th, 1996.

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