Abstract
BACKGROUND: Intranasal diacetylmorphine (IN DAM) represents a promising new route of administration, which is currently under investigation as a novel treatment approach for opioid use disorder in Switzerland. This study characterized the pharmacokinetics and pharmacodynamics of therapeutically relevant intranasal doses of DAM and its metabolites in patients with severe opioid use disorder. METHODS: In this prospective observational study, patients on intranasal heroin-assisted treatment (HAT) in Basel, Switzerland, self-administered their usual dose of IN DAM before receiving their daily maintenance dose. Inclusion criteria were age ≥ 18 years and current participation in IN HAT. Plasma concentrations of diacetylmorphine, 6-monoacetylmorphine (6-MAM), morphine, morphine-6-glucuronide, and morphine-3-glucuronide were measured using liquid chromatography-tandem mass spectrometry at baseline and at 2, 5, 10, 15, 20, 30, 40, 50, 60, 120, and 180 min. Acute subjective effects and cravings were assessed repeatedly using visual analog scales, withdrawal symptoms were measured using the Short Opiate Withdrawal Scale, and autonomic responses were recorded over the 3 h after IN DAM administration. RESULTS: In total, 14 patients were included in the study. The mean self-administered IN DAM dose was 346 mg (range 190-700 mg) delivered over a mean time of 3.8 min (range 1-9 min). IN DAM elicited moderate-to-strong peak drug effects, with marked reductions in heroin craving and withdrawal symptoms. No clinically relevant respiratory depression or decrease in oxygenation saturation was observed. Subjective effects occurred rapidly within the first 2 min after the start of administration. These effects gradually increased and peaked at 30-35 min, which paralleled the rising plasma concentrations of DAM and 6-MAM, while the sustained heroin-like effects best correlated with morphine and morphine-6-glucuronide plasma concentrations. Plasma half-lives of diacetylmorphine and 6-monoacetylmorphine were longer, and time to maximal plasma concentration was later than previously reported, suggesting saturated absorption at high intranasal doses and volumes. CONCLUSIONS: IN DAM has a good safety profile and should be considered as an effective alternative for patients in HAT, offering rapid onset of effects without significant side effects. Optimization of intranasal delivery may further improve absorption and clinical utility.