title: Intra-individual variability of the metabolic effect of inhaled insulin together with an absorption enhancer.
abstract: OBJECTIVE
  To study the metabolic effect and the variability of the effect elicited by inhalation of 87.2 U insulin powder combined with an absorption enhancer. The metabolic effect was compared with that of 10.2 U regular insulin injected subcutaneously and of 5.5 U regular insulin given intravenously
  
  
  METHODS
  In this single-center open euglycemic glucose clamp study 13 healthy male volunteers received 5 insulin administrations on separate study days: once as an intravenous dose, once as a subcutaneous injection, and 3 times by inhalation, in randomized order. Glucose infusion rates (GIRs) necessary to keep blood glucose concentrations constant at 5.0 mmol/l were determined over an 8-h period after administration.
  
  
  RESULTS
  After inhalation of the insulin powder aerosol, the onset of action was substantially more rapid than after subcutaneous insulin injection, and maximal action was reached earlier (86+/-47 vs. 182+/-53 min, P<0.0001). The maximal glucose infusion rate after inhalation of insulin was comparable to that after subcutaneous insulin injection (9.2+/-2.6 vs. 8.8+/-2.8 mg x kg(-1) x min(-1), NS). The metabolic effect in the first 2 h after inhalation was significantly greater than that after subcutaneous insulin injection (amount of glucose infused: 0.88+/-0.25 vs. 0.59+/-0.20 g x kg(-1) x 120 min(-1), P<0.0001). However, the total metabolic effect after inhalation and subcutaneous injection was comparable (2.50+/-0.76 vs. 2.56+/-0.69 g x kg(-1) x 480 min(-1), NS). The relative bioefficacy of inhaled insulin calculated in relation to the data from the subcutaneous insulin application was 12.0+/-3.5% (absolute bioefficacy 10.1+/-3.1%) but was highest in the first 2 h after application (18.5+/-3.7%; absolute bioefficacy 8.2+/-4.1%). The intraindividual variability of the metabolic response induced by insulin inhalation was 14+/-9% for the maximal glucose infusion rate, 15+/-10% for the time-to-maximal effect, and 16+/-12% for the total amount of glucose infused.
  
  
  CONCLUSIONS
  This feasibility study shows that inhaled insulin with an absorption enhancer has a pronounced metabolic effect compared with the results of a previous study of inhaled insulin without an enhancer. The intraindividual variability of the metabolic effect was comparable with that of inhaled and subcutaneously injected insulin.
authors.affiliation: Department of Metabolic Diseases and Nutrition, World Health Organization Collaborating Centre for Diabetes, Heinrich-Heine-University Düsseldorf, Germany. lutz.heinemann@profil-research.de
authors.forename: L
authors.initials: L
authors.lastname: Heinemann
authors.forename: W
authors.initials: W
authors.lastname: Klappoth
authors.forename: K
authors.initials: K
authors.lastname: Rave
authors.forename: B
authors.initials: B
authors.lastname: Hompesch
authors.forename: R
authors.initials: R
authors.lastname: Linkeschowa
authors.forename: T
authors.initials: T
authors.lastname: Heise
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D019540:Area Under Curve; D001786:Blood Glucose / Q000378:metabolism*; D018592:Cross-Over Studies; D015309:Glucose Clamp Technique; D006801:Humans; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D007328:Insulin / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male
chemical_list: D001786:Blood Glucose; D007328:Insulin