A physiologic additive for dissolving insulin crystals for parenteral application has been found. Insulin crystals are relatively insoluble in simple aqueous solutions. They will dissolve, however, in highly acidic solutions, but these are not suitable for parenteral use. Both neutral and acid pH insulin solutions have a tendency for the dissolved hormone to reaggregate. Notwithstanding possible changes in biologic activity, such formed aggregates must be prevented because they interfere with the flow in portable insulin delivery devices and result in the loss of glycemic control. The addition of 1.5% autologous serum to the aqueous diluent for insulin has eliminated these difficulties and increased by 37% the apparent biologic activity of insulin solutions prepared in this way. With this additive, continuous uninterrupted intravenous insulin infusion has provided near ideal blood glucose control in four pancreatectomized dogs for 5 mo and four patients with juvenile-onset diabetes for 18–23 days. Serum apparently contains factor(s) that promote the dissolution of insulin and prevent the formation of peptide aggregates in dilute solutions.

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