New Study Finds Acetaminophen Could Reduce Male Fertility

Acetaminophen, also called N-acetyl para-aminophenol or paracetamol, is one of the most widely used over-the-counter analgesic and antipyretic agents. Although its exact mechanism of action remains unclear, it is historically categorized along with NSAIDs because it inhibits the cyclooxygenase (COX) pathways. 

Recently different studies have shown that it can have, like any other medication, adverse effects to our health. Is a medication that has been always used because of it being less “damaging.”

A recent study from researchers from the University of Edinburgh, Scotland showed that regular acetaminophen use resulted in a significant increase in mean daytime systolic blood pressure of about 5 mm Hg when compared with placebo, which can increase the risk of cardiovascular disease. 

In another recently published study, researchers evaluated if acetaminophen had any effect in human sperm signaling and function. The research appears in the journal Human Reproduction. 

Studies have shown that adult men with high urinary levels of over-the-counter mild analgesic acetaminophen have impaired sperm motility and increased time-to-pregnancy.

The study consisted of 3 young males that were exposed to acetaminophen. The researchers evaluated the levels of the medication in the seminal plasma and found that it accumulates between 3 and 5 days after exposure.  

The researchers found that the metabolite N-arachidonoyl phenolamine (AM404), produced via fatty acid amide hydrolase (FAAH), interferes with human sperm Ca2+-signaling and function, which can interfere with sperm motility and time-to-pregnancy.


Rehfeld A, et al. Human sperm cells can form paracetamol metabolite AM404 that directly interferes with sperm calcium signalling and function through a CatSper-dependent mechanism. Hum Reprod. 2022 Mar 8:deac042. doi: 10.1093/humrep/deac042. Epub ahead of print. PMID: 35259261.

NCBI. Acetaminophen.,the%20cyclooxygenase%20(COX)%20pathways

Iain M. Maclntyre, et al. Regular Acetaminophen Use and Blood Pressure in People With Hypertension: The PATH-BP Trial. Circulation. 2022;145:416–423.  

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