Does Naproxen Cause Constipation?

Does Naproxen Cause Constipation?

Naproxen is prescription only Non-Steroidal Anti-Inflammatory Drug (NSAID). It is commonly prescribed to reduce mild-moderate pain and inflammation for musculoskeletal problems. I have written about its pain reducing effect in this post.

However, like many medications you are at risk of experiencing side effects, and a lesser know but nonetheless unpleasant side effect of Naproxen is constipation.

The Mechanism Of How Naproxen Can Contribute to Constipation

NSAIDs such as Naproxen inhibit the production of prostaglandins - which are signalling molecules that enable various bodily functions, including digestion - through the inhibition of the cyclooxygenase enzymes: COX1 and COX2. Prostaglandins such as prostaglandin E2, help promote normal gut motility through facilitating peristalsis - which is the rhythmic contraction of the intestinal muscles that assists to propel food along the bowel in preparation to be expelled from the body through defecation. Therefore, when you take Naproxen and as a result, your prostaglandin production is reduced, peristalsis is impaired and reduces the efficiency of bowel movements. This, in theory, can lead to constipation.

Another possible reason is that NSAIDs can affect the fluid balance in the gut. Prostaglandins are involved in regulating water and electrolyte transport in the gut, helping to maintain stool hydration and consistency. When prostaglandin production is inhibited, intestinal fluid secretion may decrease, resulting in drier, harder stools that are more difficult to pass and therefore increasing the risk of constipaton.

Is there any evidence for Naproxen causing constipation?

Unfortunately, many of the studies available do not directly measure the incidence of constipation; rather, they include it as a secondary finding or even anecdotal observation. However, the studies below provide relevant evidence:

• Todd & Clissold (1990) conducted a review article that evaluated naproxen’s pharmacological properties and clinical use, focusing on its efficacy and tolerability in humans. While the primary GI side effects reported were dyspepsia, nausea, and GI bleeding, constipation was noted as an occasional adverse effect in some patients, occurring less frequently than other symptoms. The study's data pooled from multiple clinical trials and post-marketing surveillance, estimated that constipation occurred in less than 3% of patients using naproxen. This was a comprehensive review drawing from a large body of clinical trials and real-world data, providing a broad perspective on naproxen’s safety profile. However, it lacked specific focus on constipation as a primary endpoint, limiting detailed analysis.

• Sevelius et al. (1980) conducted a study that assessed naproxen sodium’s bioavailability and analgesic efficacy in patients with postpartum pain. Among GI side effects, constipation was reported in 4% of patients (2 out of 50) receiving naproxen sodium compared to 2% in the naproxen group, suggesting a slightly higher incidence with the sodium salt form. The study's methodology was robust in that it used a randomised controlled trial design with a focus on clinical outcomes in a specific population, however the small sample size limits the generalisability.

Who Might Be More Susceptible To Constipation?

Certain patient sub-groups may be more prone to constipation while taking naproxen. The elderly - i.e. those aged 65 and over - often experience changes in gut motility and fluid intake. This makes them more vulnerable to bowel irregularities. Moreover, those patients with pre-existing gastrointestinal conditions, such as irritable bowel syndrome (IBS) may find that any NSAIDs including naproxen, exacerbate their symptoms.

How to prevent constipation from Naproxen?

Although the most effective way to reduce naproxen-induced constipation is to avoid Naproxen, for those whom avoiding Naproxen completely is not clinically indicated, below are some useful strategies that may help:

• Stay hydrated: increasing water intake helps to soften the stool by adding moisture to it, making it easier to pass through the intestines. Whereas, when your body is dehydrated, it absorbs more water from the stool, leading to hard, dry stools that are difficult to pass.

• Increase dietary fibre: by consuming more fruits and vegetables this increases the amount of insoluble fibre within your bowel and assists with adding bulk to the stool. A bulkider stool stimulates the intestines to contract and move waste through the digestive tract more efficiently and relieve constipation.

• Be more active: physical activity stimulates the natural contraction of intestinal muscles (i,e promotes optimum gut motility), and therefore makes them more efficient at expelling waste.

Conclusion

Naproxen is known to be effective for managing pain and inflammation, but its potential to cause constipation, though less commonly discussed may mean it is not a suitable medication for your needs. Through its inhibition of prostaglandins, naproxen may impair gut motility and alter fluid balance, theoretically increasing the risk of constipation. Studies like those I included by Todd & Clissold (1990) and Sevelius et al. (1980) provide some evidence of this side effect. Certain groups, such as the elderly or those with pre-existing gastrointestinal conditions, may be more susceptible, highlighting the need for tailored monitoring.

Evidently, avoiding naproxen is the most logical strategy that eliminates the risk of constipation, but sometimes this is not feasible, and therefore implementing practical strategies such as staying hydrated, increasing dietary fiber, and maintaining physical activity are ways to mitigate constipation for those who rely on this medication.

If you want to consult with me about a prescription for naproxen, you can do so here.

References

1. BNF. (2023). Naproxen. NICE. https://bnf.nice.org.uk/drugs/naproxen/

2. Todd, P. A., & Clissold, S. P. (1990). Naproxen: A reappraisal of its pharmacology, and therapeutic use in rheumatic diseases and pain states. Drugs, 40(1), 91–137. https://doi.org/10.2165/00003495-199040010-00006

3. Sevelius, H., Runkel, R., Segre, E., & Bloomfield, S. S. (1980). Bioavailability of naproxen sodium and its relationship to clinical analgesic effects. British Journal of Clinical Pharmacology, 10(3), 259–263. https://doi.org/10.1111/j.1365-2125.1980.tb01755.x