The subcutaneous absorption of human and bovine ultralente insulin formulations.

The subcutaneous absorption of 125I-labelled semisynthetic human ultralente insulin was compared with that of 125I-labelled beef ultralente in eight insulin-dependent diabetic patients using a balanced cross-over design. In randomized order, 6 U of human ultralente was given in the thigh and in the abdominal wall while 24 U was given in the contralateral thigh and 6 U of bovine ultralente in the abdominal wall. On a second occasion the injection sites of human and bovine ultralente were reversed. Human ultralente was absorbed significantly faster than bovine ultralente. Thus, the 50% disappearance time of the radioactivity in the thigh was 15 +/- 3 h versus 44 +/- 9 h for the high dose, and 13 +/- 2 h versus 21 +/- 5 h for the small dose for human and bovine ultralente, respectively. Correspondingly, values for the abdomen (6U) were 9 +/- 1 h and 16 +/- 2 h. The difference between the absorption rates for 6 U and 24 U was statistically significant for bovine ultralente only. Human ultralente, but not bovine ultralente showed faster absorption from the abdomen than from the thigh. The absorption rate of human ultralente insulin, though faster than bovine ultralente insulin, makes it suitable as the basal insulin preparation for multiple insulin injection regimens.