The Committee reviewed an application submitted by the Patient Association for the Preservation of Natural Animal Insulin Switzerland, Bern, Switzerland, the Insulin Forum Switzerland, Bern, Switzerland, the Insulin Dependent Diabetes Trust International, Northampton, England, and the Swiss Tropical Institute, Swiss Centre for International Health, Basel, Switzerland, for the inclusion of intermediate amorphous (100%) porcine insulin suspension (insulin "semilente"). Comments on the application were received from The Diabetes Programme, Division of Noncommunicable Diseases and Mental Health, WHO.

The Committee noted that the Model List currently includes an intermediate-acting and a short-acting (soluble) insulin, but that neither the origin (i.e. human or animal) nor the type (i.e. zinc suspension or isophane insulin) are specified. Arguments for the inclusion of the intermediate-acting "semilente" form were summarized as follows:

- it has more favourable pharmacokinetic properties than other intermediate-acting insulins and the incidence of both nocturnal hypoglycaemia and early morning hyperglycaemia is lower;

- it is the only prompt intermediate-acting insulin with added zinc ions and not bound to fish protamine;

- human insulins were introduced without any proof of superiority over animal insulins;

- some patients present loss of hypoglycaemia warning symptoms after transfer to human insulin;

- animal insulins are cheaper than the corresponding human insulins.

The Committee agreed that a number of points regarding the introduction of human insulins merit attention:

- human insulins were introduced without any proof that they are less immunogenic than animal insulins;

- the number of patients participating in randomized trials has been limited (2156 in the recent Cochrane Review (17)) and the mean duration of such trials short (5.8 months);

- the frequency of insulin resistance has not been assessed.

Furthermore, the transfer to human insulins has been associated with a higher risk of severe hypoglycaemia in some studies; however, this finding is not universal. According to the Cochrane Review, the frequency of hypoglycaemic episodes is similar with both types of insulins (17).

In the light of the conclusion of the 2003 Cochrane Review, namely that there are no clinically relevant differences between animal and human insulins (17), the Committee concluded that the choice between the two types of insulin should be made on the basis of cost. Noting that intermediate-acting insulin was already on the Model List, the Committee further concluded that insufficient evidence had been presented to justify a decision to single out a species-specific insulin.