147-OR: Revisiting the Impact of Opioid Receptor Blockade on Hypoglycemia-Associated Autonomic Failure (HAAF)

HAAF, which has been defined as >20% reduction in average epinephrine (Epi) levels following recurrent hypoglycemia (PMID: 28911152), complicates insulin therapy in T1D. We previously showed that activation of opioid receptors induces HAAF, while intravenous (IV) administration of the opioid receptor antagonist naloxone prevents HAAF. Because of its wide clinical use and possible direct CNS effects, we examined the effects of intranasal naloxone (IN) on hypoglycemia and HAAF.

Seventeen (15M, age 43.8±8.7) healthy adults were enrolled in a randomized, placebo-controlled, cross-over, double-blinded study in which they underwent three hyperinsulinemic hypoglycemic clamp studies (duration 2h, glucose nadir 54 mg/dL), with administration of IN (4mg) or placebo during the first two clamps. Two subjects were excluded for lack of Epi response to hypoglycemia. Nine of the remaining 15 subjects developed HAAF, confirming inter-individual variability in susceptibility to HAAF (PMID: 32915987, 35475026).

Among the 15 subjects included in the analysis, Epi levels trended downward between the 1st and 3rd clamps in placebo studies (mean ± SEM: 677 ± 114 vs. 512 ± 78 pg/mL, p=0.054), whereas Epi levels remained stable in IN studies (1st vs. 3rd: 519 ± 70 vs. 487 ± 77 pg/mL, p= 0.69). Among the 9 subjects who developed HAAF, Epi levels during the 1st clamp were significantly lower with IN vs. placebo (493 ± 102 vs. 858 ± 161 pg/mL, p=0.03), but there was no further reduction in Epi with IN (1st vs. 3rd: 493±102 vs. 539±101 pg/ml, p=0.67).

In summary, these studies suggest differential effects of intranasal naloxone on initial vs. repeated hypoglycemic episodes. Specifically, IN may be effective in preventing Epi blunting during repeated exposure to hypoglycemia. In subjects susceptible to HAAF, IN may paradoxically blunt the Epi response to initial hypoglycemic exposure. Future studies should investigate the clinical significance of initial vs. ongoing epinephrine responses to hypoglycemia.