GB860515A - Improvements in or relating to insulin preparations - Google Patents

Abstract

Aqueous injectable insulin crystal suspensions having a protracted effect are prepared by suspending, in an aqueous medium, insulin crystals originating from ox or calf pancreas and having a rhombohedral structure and the form of twin crystals, "stars" or deformed rhombohedrons. The suspension is given a pH of about 7 (6.5 to 7.5), the content of crystallization promoting metals, viz. zinc (preferred), cadmium, cobalt, nickel and copper being adjusted so that the suspended insulin crystals contain less than 0.25 milliequivalent thereof per gram of the dried crystals at pH 7.0 of the suspension medium. Pre-prepared crystals may be suspended in an injectable medium to produce preparations according to the invention or, alternatively, the insulin may be crystallized under sterile conditions in a crystallization medium which is suitable for injection and to which water, isotonics, and preservatives may be added. Preferably, the aqueous medium does not contain substances, e.g. buffers which form complexes or slightly soluble compounds with the free metal ions, in which case the total amount of metal ions in the suspension is not allowed to reach 13 X A X 10-3 milliequivalents/litre, A being the number of international units of insulin per ml. If a more pronounced initial effect is required, a solution at the same pH of insulin derived from pig pancreas may be added. Specification 840,870 is referred to.