Does Diclofenac have sulfa in it? 

Diclofenac does not contain a Sulfonamide moiety in its chemical structure. Therefore, it is safe for you to use this medication if you have a sulfa allergy (1,2,3).

However, it is essential to remember that, even if you do not have a sulfa allergy or are not allergic to diclofenac itself, you may still experience adverse effects from this medication (4).

Does Diclofenac have sulfa in it? 

No, Diclofenac is not a sulfa drug. 

This medication is an over-the-counter (OCT) non-steroidal anti-inflammatory drug (NSAID) that is generally available as Diclofenac sodium and Diclofenac potassium. 

It does not contain Sulfonamide moiety in its chemical structure. Therefore, it can not be classified as a sulfa drug. 

It is important to know that, although many NSAIDs are considered to be free from sulfa moiety, some NSAIDs, such as Celecoxib and Valdecoxib, may trigger an allergic reaction in people who are sensitive to Sulfonamides (1,2,3).

Can you take Diclofenac if you are allergic to Sulfonamides?

You can take Diclofenac if you’re allergic to Sulfonamides since it does not contain that particular chemical moiety. 

However, a small number of people could be allergic to Diclofenac, and definitely shouldn’t take this medication. If you’re only allergic to sulfa drugs, it shouldn’t stop you from taking Diclofenac. 

It is important to take into account that, just like all medications, Diclofenac can cause some adverse reactions even if you are not allergic to sulfa or to Diclofenac itself. These reactions may include:

  • Edema
  • Nausea
  • Headache
  • Dizziness
  • Vomiting
  • Constipation
  • Pruritus
  • Diarrhea
  • Flatulence
  • Pain in extremity
  • Abdominal pain
  • Sinusitis
  • Increased alanine aminotransferase
  • Increased blood creatinine
  • Hypertension
  • Dyspepsia

Remember that NSAIDs pose an elevated risk of serious cardiovascular thrombotic events such as heart attacks and strokes, as well as an increased risk of significant gastrointestinal adverse events. 

Other potentially serious adverse effects may occur (4). Please contact your doctor if you experience any unwanted effects while taking this medication.

Diclofenac stays in your system for about 15-20 hours, after which the side effects start to fade away.

What medications trigger an allergic reaction if you are allergic to Sulfonamides?

There are some medications which contain Sulfonamide moiety in their chemical structure and you should stay away from those meds if you have a sulfa allergy. These medications include (3):

  • Sulfonamide antibiotics (oral and topical preparations) – Sulfamethoxazole+Trimethoprim (Bactrim, Septra), Sulfadiazine, Sulfacetamide, and Silver Sulfadiazine
  • Some Diuretics – Hydrochlorothiazide, Furosemide, and Bumetanide.
  • Some NSAIDs – Celecoxib and Valdecoxib
  • Some disease-modifying antirheumatic drugs (DMARDs) – Sulfasalazine.

In addition to the examples mentioned above, there are other medications that contain Sulfonamide in their chemical structure. Inform your doctor if you are allergic to sulfa, so that they can always recommend a safe treatment for you.


In this brief article, we have discussed the presence of sulfa in Diclofenac and its safety profile for individuals with sulfa allergies. Additionally, we touched upon potential adverse effects of Diclofenac and listed some medications to avoid if you have a sulfa allergy.

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