Veterinary Medicine - May 2008 - (Page c9) Using porcine zinc insulin suspension in the management of canine diabetes mellitus David Bruyette, DVM, DACVIM Medical Director VCA West Los Angeles Animal Hospital Los Angeles, Calif. Vetsulin (porcine insulin zinc suspension, Figure 1, page 10) is the rst FDAapproved veterinary product indicated for the reduction of hyperglycemia and hyperglycemia-associated clinical signs in dogs with diabetes mellitus. It is registered in 24 other countries as Caninsulin and has been used since 1990. Vetsulin is supplied as a sterile injectable suspension in multidose vials containing either 2.5 ml or 10 ml of 40 U/ml (U-40) porcine insulin zinc suspension.Vials are supplied in cartons of one 10-ml vial and cartons of 10 2.5-ml vials and should be kept refrigerated. It is recommended to replace opened vials on a monthly basis. Pharmacokinetics Vetsulin is a sterile, aqueous suspension of puri ed porcine insulin. It contains 40 U/ml, consisting of 30% amorphous and 70% crystalline zinc insulin in a neutral bu er at a pH of 7.35.Vetsulin is a lente, or intermediate-acting, insulin. In dogs, the amorphous fraction has peak activity approximately four hours after subcutaneous administration, and its e ects last for about eight hours. Thereafter, the e ect is maintained by the crystalline fraction, which has a slower onset of action and peak e ects around 11 hours following the injection (Figure 2, page 12). Afterward, the e ect gradually declines to zero. Vetsulin should not be diluted because the amount of soluble insulin is increased by the aqueous diluent used, which results in an alteration of the pharmacokinetics. With a larger aqueous fraction and smaller crystalline fraction, a decrease in the crystalline portion responsible for the second peak of insulin activity would occur. As porcine insulin,Vetsulin has the same amino acid sequence as canine insulin. This may help decrease the risk of anti-insulin antibody development, which may interfere with the action of the insulin. In a recent study, the presence of anti-insulin antibodies was determined by ELISA in serum samples from 30 diabetic dogs receiving bovine insulin therapy and 30 normoglycemic dogs.1 Twenty of the diabetic dogs had signi cant reactivity to both bovine (heterologous) and porcine (homologous) insulin compared with control dogs. In contrast, researchers saw no signi cant di erence between the two populations in reactivity to canine distemper virus or canine thyroglobulin. The high degree of correlation between anti-bovine insulin and anti-porcine insulin antibodies suggested cross-reactivity, which was conrmed by performing a competition ELISA, which showed antibody binding to bovine insulin inhibited by pre-incubating serum with porcine insulin. 9 c12
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