Effects of Intramuscular (IM) Oxytocin on Pupil Diameter and Heart Rate Variability (HRV)

What Was Tested

This registered phase 4 trial tested Oxytocin for chronic pain: fibromyalgia & crps.

The goal of this study is to test the effects of oxytocin on heart rate variability and pupil diameter, both of which have subtle effects on the activity rate of the autonomic nervous system.

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

The registry classes the interventions as drug.

More on the Plan

This protocol focuses on two measures of autonomic control to quantify central actions of oxytocin.

First, the study team proposes to examine the influence of oxytocin on heart rate variability with focus on its effect on high frequency variability, most commonly ascribed to parasympathetic nervous system activity acting to brake sympathetic tone.

As a secondary assessment of parasympathetic activity, the study team will measure low frequency fluctuation in pupil diameter, termed hippus, which also reflects parasympathetic nervous system activity.

This outcome measure can be assessed in 3 seconds using equipment currently being used under Institutional Review Board (IRB) approved protocols.

Who Took Part

The registry lists 22 actual participants took part.

It was open to people of any sex aged from 18 years up to 66 years.

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

Examples of who could join: Male or female \> 18 and \< 66 years of age,. Body Mass Index (BMI) \<40. Normal blood pressure and resting heart rate without medication.

The full record lists 4 inclusion and 6 exclusion criteria; among the exclusions: women who are pregnant (positive result for serum pregnancy test at screening visit),; women who are currently nursing or lactating, women that have been pregnant within 2 years; neuropathy, chronic pain, diabetes mellitus, or taking benzodiazepines or pain medications on a daily basis.

How the Study Was Run

The set-up was randomized, crossover and triple-blind.

Random assignment meant chance, not the researchers, decided who got Oxytocin and who got the comparison, which limits bias.

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

Blinding on both sides kept the chronic pain: fibromyalgia & crps participants and researchers unaware of who received Oxytocin.

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

It started in 2019-10-24 with completion listed for 2021-11-01.

It ran at 1 site in United States.

Its stated primary purpose is basic science.

What Was Measured

Primary outcome: Fluctuation in Pupil Diameter (Hippus) -Pre Drug Administration (time frame: From 20 minutes before until study drug injection). Fluctuation in Pupil Diameter (Hippus) -Post Drug Administration (time frame: For 90 minutes after study drug administration). Fluctuation in Pupil Diameter (Hippus) -Post Drug Administration (time frame: For 120 minutes after study drug administration).

What This Means in Plain Language

Put simply, this is a phase 4, randomized trial of Oxytocin in 22 people with chronic pain: fibromyalgia & crps.

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

The trial is marked completed; results are posted on the registry, and this page does not restate them.

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