Oxytocin is a hormone produced by the human body. It should not be confused with the opioids OxyContin or oxycodone. This was going to be a piece on how oxytocin is good for pain relief, except that is not so for women.
Oxytocin — Multiple effects
Oxytocin is a peptide hormone made of nine amino acids and is secreted by the posterior pituitary gland in the brain… Oxytocin plays a well-known role in pregnancy-related uterine contractions and lactation... Oxytocin has been shown to modulate the stress response... Oxytocin facilitates human sociability, including trust, attachment and intimacy...it may influence mood and ameliorate feelings of depression.
Oxytocin Pain Studies
According to this review using oxytocin for pain seems like a good idea:
Oxytocin – A Multifunctional Analgesic for Chronic Deep Tissue Pain
The present article reviews the existent human and basic science data related to the direct and indirect effects of oxytocin on pain. Due to its analgesic, anxiolytic, antidepressant and other central nervous system effects, there is strong evidence that oxytocin and other drugs acting through the oxytocin receptor could act as multifunctional analgesics with unique therapeutic value...there is evidence linking it to CNS functions including those modulating anxiety, depression and reward systems.… the majority of these studies have found that exogenous OXY administration is reliably associated with decreases in pain sensitivity.
This study was published subsequent to the foregoing review:
In a Double Blind, Placebo Controlled Cross Over Study oxytocin was demonstrated to reduce the perception of pain [in men]:
In the present study, we investigated the analgesic effects of 40 IU of intranasal oxytocin in 13 healthy male volunteers using a double‐blind, placebo‐controlled, cross‐over design and brief radiant heat pulses generated by an infrared laser
…
Intranasal oxytocin significantly reduced subjective VAS [visual analog scale pain] ratings
Good as far as it goes, but they should have tested women too. Someone did, and published in 2017:
Sex-specific effects of intranasal oxytocin on thermal pain perception: A randomized, double-blind, placebo-controlled cross-over study
Whether these sex differences apply in relation to pain experience is not known. This is because previous studies have either examined the effects of oxytocin only in male rodents (e.g., Yang et al., 2011), and many studies in humans only recruited men (Paloyelis et al., 2016;Singer et al., 2008; Zunhammer et al., 2015), or if they recruited both men and women, they failed to analyze the data with respect to sex (Rash and Campbell, 2014). Therefore, while oxytocin seems to have a hypoalgesic effect, it remains unknown whether these effects are sex specific, or if they occur in persons with chronic pain...[emphases added]
In women with CNSP [Chronic neck and shoulder pain], the [brief] 45 °C thermal heat stimuli were perceived as more intense following oxytocin ... compared to following placebo administration (... p= 0.004...). This is a clinically meaningful hyperalgesic effect...and represents a 26.6% increase in perceived pain intensity of a stimulus following oxytocin administration. No other pairwise comparisons remained significant ...
Sex-specific effects of oxytocin have previously been shown in other contexts. For example, Kirsch et al. (2005) reported that oxytocin potently reduced amygdala activation in healthy males presented with fear-inducing visual stimuli, whereas Domes et al. (2010) reported that oxytocin administration increased amygdala activation in healthy females when presented with fear-inducing visual stimuli.
These charts are taken from the foregoing study. What they show is that oxytocin has no effect on pain perception among healthy controls of either sex. For men with chronic pain it helps a little bit. For women with chronic pain adding oxytocin hurts. A lot. Note that this adverse effect shows up only for the combination of female gender and chronic pain. How many pain studies neglect to address this particular combination?
There is more - this 2018 study looked at the effect of sleep deprivation upon men and women:
Sleep Deprivation Related Changes of Plasma Oxytocin in Males and Female Contraceptive Users
Compared to the HS [habitual sleep] condition, the plasma OT [oxytocin] concentration was significantly increased in sleep deprived females (p = 0.02) but not males (p = 0.69). ...We found a positive correlation between anxiety-scores and OT (p = 0.021), which was enhanced when respecting “sex” (p = 0.008) and “sleep” (p = 0.001) in a hierarchical regression analysis.
Sleep deprived women experience elevated oxytocin whereas men do not. Per the previous study elevated oxytocin and chronic pain results in increased pain for women, only. So sleep deprived women with chronic pain can be expected to be in more pain than men. What other stressful conditions cause women with chronic pain to experience more pain than men?
Compiling this report required flexibility of mind because I did not encounter the pain study of women until late Friday. I was set to go with a piece on how oxytocin was beneficial for pain. What a disservice that would have been! Male doctors who are dismissive of women's pain are likely lacking such essential information.
Investigators prefer to study men because the menstrual cycle adds an additional variable that needs to be taken into account. How many substances intended for pain relief have contradictory effects on women in chronic pain? Effects that are unknown because they have never been studied?
Medical journals are full of surprises.