16 October 2020

The Painkiller’s Other Effects

Welcome back. In my last blog post, I bashed dietary supplements pitched to bolster memory and cognition (see Brain Health Supplements). I should move on to something, anything, other than pharmaceuticals, but there’s a recent study that added to others I’d been saving on drugs with acetaminophen.

Do you recognize the name? Acetaminophen is an active ingredient in more than 600 over-the-counter and prescription medicines, including Tylenol. As the U.S. Food and Drug Administration describes, the drug relieves pain and fever and is also combined with other active ingredients in medicines that treat allergy, cough, colds, flu and sleeplessness.

Extra strength Tylenol with 500 mg of acetaminophen
in each caplet
(from www.walmart.com).

There are well recognized safety concerns associated with acetaminophen, and there are those that have been flagged in the recent and other studies over the past decade. I’ll start with the former, then highlight the latter.

Acetaminophen Safety
Like any drug, the principal safety concern is taking more than directed, which can occur inadvertently given the number of products with the drug. Acetaminophen can cause severe liver damage and a rare, serious skin reaction.

The FDA has taken action to protect consumers, such as limiting the strength, and billions of doses of acetaminophen are taken safely every year. Still, about 450 deaths occur yearly from overdoses, and some 50,000 people end up in the emergency room.

Now that I’ve alerted--OK, frightened--you with the principal safety concern, here are concerns that might deserve more attention from pharmaceutical companies and the government.

Corididin HBP Cold&Flu with 325 mg of acetaminophen
in each tablet
(from www.walmart.com).
Reduces Social Pain -- A University of Kentucky researcher led a study published in 2010. Hypothesizing that physical and social pain may rely on some of the same mechanisms, they conducted two experiments to gauge if acetaminophen would reduce behavioral and neural responses to social rejection. Testing doses of the drug or a placebo in one experiment, they found acetaminophen reduced reports of social pain on a daily basis. Using functional magnetic resonance imaging to measure participants’ brain activity in the second experiment, they found the drug reduced neural responses to social rejection in brain regions associated with distress caused by social pain and the affective component of physical pain.

Reduces Empathy for Pain – In a 2016 study, researchers with the National Institutes of Health and Ohio State University conducted double-blind, placebo-controlled experiments with acetaminophen. They had participants rate perceived pain, personal distress and empathic concern in response to reading scenarios about physical or social pain, witnessing ostracism in the lab, or visualizing another participant being subjected to painful noise blasts. Acetaminophen reduced empathy to others’ pain. It also reduced the unpleasantness of noise blasts, which mediated the drug's effects on empathy.

Reduces Positive Empathy -- Extending earlier findings that acetaminophen reduces empathy for other people’s suffering, researchers with Ohio and Ohio State universities tested whether the drug also impaired positive empathy, the sharing of others’ positive emotions. In a 2019, double-blind, placebo-controlled experiment, they measured different aspects of positive empathy while participants read scenarios of uplifting experiences. Acetaminophen reduced personal pleasure and other empathic feelings in response to the scenarios. Because positive empathy is related to prosocial behavior, the findings raised questions about the societal impact of excessive acetaminophen consumption.

Alters Perception of Risk -- For the most recent study, researchers with Ohio State and Oregon universities tested the hypothesis that acetaminophen could influence judgments and decisions regarding risk. In three double-blind, placebo-controlled experiments, they had participants complete a standard laboratory measure of risk taking (Balloon Analog Risk Task) and two separate tests with self-reported measures of risk perception. Across all studies, acetaminophen increased risk-taking behavior.

Midol Complete with 500 mg of acetaminophen
in each gelcap
(from www.amazon.com).
Wrap Up
I’m going to presume that the relevant pharmaceutical companies and possibly FDA are aware of these and related studies of acetaminophen. Recognizing the studies are few and being way out of my lane as usual, I’ve no idea if or when the research might warrant further work to confirm the findings and fully characterize the psychological effects.

Given the nature of the effects and the millions of people who take the drug, it would seem there should be some response. Anyway, I thought the work was interesting and hope you did, too. Thanks for stopping by.

Common medicines containing acetaminophen: www.bemedwise.org/health-research-and-reports/health-resources-and-toolkits/acetaminophen/acetaminophen-containing/
Acetaminophen and Tylenol background:
Studies and articles on research cited:
Multiple effects:
Reduces social pain:
Reduces empathy for pain: academic.oup.com/scan/article/11/9/1345/2224135
Reduces positive empathy: www.frontiersin.org/articles/10.3389/fpsyg.2019.00538/full
Alters perception of risk:

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