Context: Hypoglycemia-associated autonomic failure (HAAF), defined as blunting of counterregulatory hormone and symptom responses to recurrent hypoglycemia, remains a therapeutic challenge in diabetes treatment. The opioid system may play a role in HAAF pathogenesis since activation of opioid receptors induces HAAF. Blockade of opioid receptors with intravenous naloxone ameliorates HAAF experimentally yet is not feasible therapeutically.
Objective: To investigate the effects of opioid receptor blockade with intranasal naloxone on experimentally induced HAAF.
Design: Randomized, double-blinded, placebo-controlled crossover study.
Setting: Academic research center.
Participants: Healthy nondiabetic volunteers.
Interventions: Paired 2-day studies, 5 to 10 weeks apart, each consisting of 3 consecutive hypoglycemic episodes (hyperinsulinemic hypoglycemic clamps, glucose nadir: 54 mg/dL): 2 on day 1 with administration of intranasal naloxone vs placebo, followed by the third episode on day 2.
Main outcome measures: Differences in counterregulatory hormones responses and hypoglycemia symptoms between first and third hypoglycemic episodes in naloxone vs placebo studies.
Results: Out of 17 participants, 9 developed HAAF, confirming variable interindividual susceptibility. Among participants susceptible to HAAF, naloxone maintained some hormonal and symptomatic responses to hypoglycemia and prevented the associated requirement for increased glucose infusion. Unexpectedly, naloxone reduced plasma epinephrine and GH responses to the first hypoglycemic episode but prevented further reduction with subsequent hypoglycemia.
Conclusion: This is the first study to report that intranasal naloxone, a widely used opioid receptor antagonist, may ameliorate some features of HAAF. Further investigation is warranted into mechanisms of variable interindividual susceptibility to HAAF and the effects of intranasal naloxone in people with diabetes at risk for HAAF.
Keywords: HAAF; counterregulatory responses; hypoglycemia; hypoglycemia unawareness; hypoglycemia-associated autonomic failure; intranasal naloxone; opioid receptors.
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