Study objectives: To determine the efficacy of the lung as an alternative route of delivery for insulin in controlling glucose below diabetic levels (11.2 mmol/L) 2 h after the ingestion of a meal in patients with type 2 diabetes mellitus.
Design: Single-blinded, nonrandomized, placebo-controlled pilot study consisting of two visits.
Setting: A primary care facility.
Patients: Seven patients with type 2 diabetes mellitus.
Interventions: On the first study visit, fasting glucose levels were normalized. Then, patients inhaled 1.5 U/kg insulin by aerosol into the lungs 5 min before ingesting a test meal. On the second visit, patients inhaled placebo aerosol 5 min before ingesting the same meal. On both visits, plasma samples were collected and analyzed for glucose levels for 3 h during the postprandial state.
Measurements and results: No one coughed after inhalation of insulin aerosol or demonstrated hypoglycemia. During the postprandial period, glucose levels were significantly lower at 20 min (5.12 ± 1.08 mmol/L), 1 h (7.87 ± 0.73 mmol/L), 2 h (8.05 ± 1.24 mmol/L) and 3 h (7.50 ± 1.43 mmol/L) following inhalation of insulin than when the placebo was used. Data for the placebo were 10.36 ± 1.23 mmol/L at 20 min, 14.0 ± 1.68 mmol/L at 1 h, 16.18 ± 1.45 mmol/L at 2 h, and 14.37 ± 2.11 mmol/L at 3h (for all comparisons, p < 0.05). On the insulin visit, glucose levels were < 11.2 mmol/L 2 h after the meal in six of seven patients. None attained this level at the placebo visit. In addition, glucose levels were within the normal postprandial range of < 7.84 mmol/L in four of seven patients 2 h after eating on the insulin visit.
Conclusions: These results suggest that, once plasma glucose levels are normalized, postprandial glucose levels can be maintained below diabetic levels by delivering 1.5 U/kg insulin into the lungs 5 min before the ingestion of a meal.