Generate and Test the Reliability of a PD Model of OXT on Pupillary Hippus as a Measure of CNS Activity

What Was Tested

This registered phase 2 trial tested Oxytocin for chronic pain: fibromyalgia & crps.

The purpose of this research is to evaluate the effects of oxytocin (naturally occurring hormone) given by an intramuscular (IM; into the muscle) injection, has on your parasympathetic nervous system.

It had two arms (groups): Oxytocin First, then Placebo (other) and Placebo, Then Oxytocin (other).

Subjects in this arm will receive Intramuscular injection of Oxytocin (Pitocin®) first then placebo injection.

Subjects in this arm will receive Intramuscular placebo injection first then oxytocin injection.

The registry classes the interventions as drug.

More on the Plan

Study participants will come to the Pain Clinical Research Unit on 2 occasions.

The order in this cross-over study will be randomized and double blind, and the studies separated by at least 48 hours.

Every 2.5 minutes beginning 20 minutes before injection and until 180 minutes after injection oscillation in pupil diameter at low frequency (hippus) will be obtained using an infrared pupilometer, in which they focus on a central point of gaze for 20 seconds.

After 180 minutes the study participant will be discharged from the Pain Clinical Research Unit.

Who Took Part

The registry lists 4 actual participants took part.

It was open to people of any sex aged from 18 years up to 75 years.

Healthy volunteers could join, not only people with the condition.

Examples of who could join: Male or female \> 18 and \< 75 years of age, Body Mass Index (BMI) \<40.

The full record lists 4 inclusion and 5 exclusion criteria; among the exclusions: subjects with neuropathy, chronic pain, diabetes mellitus, or taking benzodiazepines or pain medications on a daily basis; subjects with eye pathology, eye surgery, or taking topical eye medications, or any disease process that would cause motor tremors or excessive eye movements.

How the Study Was Run

It was run as a randomized, crossover and triple-blind study.

The chronic pain: fibromyalgia & crps participants were allocated by chance, so the Oxytocin group and the comparison group should start out alike.

Each person switched between Oxytocin and the comparison at some point, usually with a gap in between.

As a double-blind Oxytocin study, the assignments were hidden from both participants and investigators until the end.

Those kept unaware of assignments: participant, investigator and outcomes assessor.

It started in 2020-11-30 with completion listed for 2026-08-01.

It ran at 1 site in United States.

Its stated primary purpose is basic science.

What Was Measured

The main thing measured (primary outcome): Fluctuation in Pupil Diameter (Hippus) -Pre drug administration (time frame: Baseline before study drug administration). Fluctuation in Pupil Diameter (Hippus) -Post drug administration (time frame: up to 180 minutes after study drug administration).

What This Means in Plain Language

Put simply, this is a phase 2, randomized trial of Oxytocin in 4 people with chronic pain: fibromyalgia & crps.

Its size is small, so on its own it can only give an early look.

It ended early (terminated); no results are posted to the registry yet, so nothing here describes outcomes.

More context: the Oxytocin compound page, Chronic pain: fibromyalgia & CRPS research.