ABSORPTION OF RAPID-ACTING INSULIN IN OBESE AND NONOBESE NIDDM PATIENTS

OBJIECTIVE-To study the absoprtion rate of rapid-acting insulin from s ubcutaneous injection sites in nonobese and obese non-insulin-dependen t diabetes mellitus (NIDDM) patients. RESEARCH DESIGN AND METHODS-Ten nonobese and 10 obese NIDDM patients (body mass indexes 24.1 +/- 0.4 a nd 31.4 +/- 0.8 kg/m(2), respectively) received four subcutaneous inje ctions of I-125-labeled rapid-acting insulin (Actrapid Human, 5 U). th ree in the abdominal wall above, lateral to, and below the umbilicus; and one in the thigh. The depth of the subcutaneous fat layer was meas ured using ultrasound techniques. The residual radioactivity was monit ored externally for 270 min. RESULTS-The disappearance half-life of I- 125-insulin was between 4 and 6 h from all injection sites, with the e xception of the upper abdominal area in the nonobese subjects, where i t measured similar to 3 h. The residual radioactivity did not differ b etween nonobese and obese patients measured from any of the sites. In the nonobese group, the most rapid absorption of I-125-insulin was fou nd from the upper abdominal area and the slowest from the thigh. In th e obese group, the absorption rates did not differ between sites. No c orrelation was found between the depth of the fat layer and the residu al radioactivity when measured at any site. CONCLUSIONS-Our results in dicate that the absorption of rapid-acting insulin is markedly slow in both obese and nonobese NIDDM patients compared with IDDM patients an d healthy subjects studied previously. In the nonobese group, the most rapid absorption of I-125-insulin is obtained after injection into th e upper abdominal area. Inter- and intraregional differences are small in the obese patients. Consequently the choice of injection site is o f little importance in this group.