Background: This study examined the effect of synthetic oxytocin delivered intranasally on acute pain sensitivity using a placebo-controlled, double-blind, within-participant crossover design.
Methods: Thirty-seven (18 were male) pain-free young adults underwent two laboratory sessions separated by 1 week. Each session consisted of baseline, administration, second baseline, pain, and recovery phases, completed in a fixed order. Participants were given an intransal administration of 40 IU oxytocin or placebo. Blood pressure and heart rate (HR) were measured at 1-minute intervals throughout each phase. Pain was induced by submersing the nondominant hand in cold (2°C) water. Pain threshold, intensity, unpleasantness, and Short-Form McGill Pain Questionnaire-2 pain descriptors were rated immediately after pain testing. Mood was assessed using visual analog scales after baseline, second baseline, and pain phases. The second laboratory session was identical to the first, with the exception that a different nasal spray was administered.
Results: Participants reported lower pain intensity (50.57 [20.94] versus 56.73 [20.12], p = .047), pain unpleasantness (47.00 [27.24] versus 55.78 [22.46], p = .033), and Short-Form McGill Pain Questionnaire-2 pain descriptors (53.38 [31.18] versus 60.92 [31.17], p = .031) and higher pain threshold (45.70 [59.55] versus 38.35 [59.12], p = .040) after oxytocin administration relative to placebo. There was a nasal spray by phase interaction on HR (p = .006). Pain-related increase in HR was attenuated by oxytocin nasal spray. Systolic and diastolic blood pressure increased during pain testing but were unaffected by nasal spray.
Conclusions: These results suggest that oxytocin can lead to decreased acute pain sensitivity.