Intoxication and other subjective effects of preanesthetic opioids in surgical patients: A randomized controlled trial.

Opioids are often administered before anesthesia to reduce stress/discomfort or enhance well-being, despite limited supporting evidence. This double-blind, randomized controlled trial investigates the acute subjective effects of intravenous morphine (10 mg), oxycodone (5 mg), and fentanyl (0.1 mg) in 199 adults undergoing elective surgery (ASA physical status I-II). All patients received a standardized multimodal preoperative medication. Patients rated their experiences on 0-10 verbal numerical rating scales immediately before and 3 min after opioid administration. The most prominent drug effects were undesirable (intoxication, sedation, and dizziness). Fentanyl produced higher ratings of intoxication, sedation, dizziness, and euphoria than morphine, with oxycodone generally showing intermediate effects. Substantial interindividual variability was observed across all treatment groups. Desirable effects (reduced anxiety and increased relaxation) were modest, and only 23% of patients reported feeling better. Notably, 96% reported feeling intoxicated. These results challenge the use of preoperative opioids to improve patient comfort. EudraCT: 2020-004920-40.