A combined rapid acting-
long acting insulin formulation has been developed wherein the pH of the
rapid acting insulin is adjusted so that the
long acting glargine remains soluble when they are mixed together. In the preferred embodiment, this injectable
basal bolus insulin is administered
before breakfast, provides adequate bolus
insulin levels to cover the
meal, does not produce
hypoglycemia after the
meal and provides adequate
basal insulin for 24 hours. Lunch and dinner can be covered by two bolus injections of a fast acting, or a rapid acting or a very
rapid acting insulin. As a result, a patient using intensive insulin therapy should only inject three, rather than four, times a day. Experiments have been performed to demonstrate, the importance of the addition of specific acids to hexameric insulin to enhance speed and amount of absorption and preserve bioactivity following dissociation into the monomeric form by addition of a chelator such as EDTA. As shown by the examples, the preferred acids are aspartic, maleic, succinic, glutamic and
citric acid. These are added in addition to a chelator, preferably
ethylenediaminetetraacetic acid (EDTA). The results show that the
citric acid formulation was more effective at dropping the blood glucose rapidly than the identical rapid acting formulation prepared with HCl in swine. Charge masking by the polyacid appears to be responsible for rapid insulin absorption. EDTA was not effective when used with
adipic acid,
oxalic acid or HCl at hastening the absorption of insulin. These results confirm the results seen in clinical subjects and patients with diabetes treated with the
rapid acting insulin in combination with
citric acid and EDTA.