Diclofenac: 7 things you should know

Medically reviewed by Carmen Pope, BPharm. Last updated on Oct 3, 2023.

1. How it works

• Diclofenac may be used to treat various pain or inflammatory conditions.
• Diclofenac works by blocking the effects of cyclooxygenase (COX) enzymes. This prevents prostaglandin synthesis (prostaglandins elevate body temperature and make nerve endings more sensitive to pain transmission).
• Diclofenac belongs to a class of medicines known as NSAIDs (nonsteroidal anti-inflammatory drugs).

2. Upsides

• Used to relieve mild-to-moderate acute pain associated with osteoarthritis and rheumatoid arthritis.
• May also be used to relieve mild-to-moderate pain due to other causes.
• Diclofenac reduces inflammation and lowers temperature.
• May also be used in the treatment of ankylosing spondylitis (a form of spinal arthritis).
• Generic diclofenac is available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

• Stomach-related side effects such as indigestion, belching, heartburn, and bleeding. People of an older age, taking other medicines that affect the stomach, or who drink more than 3 glasses of alcohol per day may be more at risk. Diclofenac is more likely than ibuprofen to cause stomach-related side effects.
• Water retention, headache, constipation, and nausea.
• Other side effects including tinnitus (ringing in the ears) have also been reported.
• Most NSAIDs have been associated with an increased risk of serious cardiovascular events including stroke or heart attack. The risk may be higher in patients with pre-existing cardiovascular conditions and with higher dosages. Diclofenac may be associated with a higher risk compared with other NSAIDs, such as ibuprofen.
• May increase bleeding time especially if given with other medicines that also delay blood clotting.
• May not be suitable for some people including those with kidney disease, a history of stomach ulcers or other gastrointestinal disorders, or with pre-existing cardiovascular disease. Should not be given during or following coronary artery bypass graft surgery.
• May interact with some other medicines such as warfarin, SSRIs, ACE inhibitors, and diuretics.
• NSAIDs, such as diclofenac, should not be used during the last three months of pregnancy because they can cause premature closure of the fetal ductus arteriosus. In addition, the use of NSAIDs at around 20 weeks gestation or later in pregnancy may cause fetal kidney problems leading to oligohydramnios (low amniotic fluid volume) and in some cases kidney impairment. If NSAID treatment is deemed necessary between 20 and 30 weeks of pregnancy, use the lowest effective dose for the shortest possible time. Avoid NSAIDs after 30 weeks gestation.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

• Diclofenac is an effective medicine for relieving pain but may be associated with an increased risk of cardiovascular and gastrointestinal side effects compared with some other NSAIDs.

5. Tips

• Different formulations of diclofenac may not be equivalent; do not interchange products without first talking with your doctor or pharmacist.
• May make your skin more sensitive to the sun; wear sunblock SPF 30-50+ when outside; see a doctor as soon as possible if you develop a skin rash.
• Should not be taken for long periods, especially by seniors.
• Blood counts and liver enzymes may need monitoring periodically.
• NSAIDs should not be used in the last 3 months of pregnancy; always ask your doctor before using any medication during pregnancy.
• If you have experienced asthma-like symptoms, developed hives (urticaria), or other allergic-type reactions in the past after taking aspirin or other NSAIDs (like ibuprofen), do not take diclofenac.
• Combining diclofenac with alcohol may increase the risk of stomach ulcers or bleeding.
• NSAIDs, such as diclofenac, should not be used in the last 3 months of pregnancy; always ask your doctor before using any medication during pregnancy. Do not use NSAIDs such as diclofenac between 20 and 30 weeks gestation without your doctor's advice because this may cause kidney problems and low amniotic fluid volumes in the newborn. Acetaminophen may be considered to treat pain and inflammation during pregnancy.

6. Response and effectiveness

• Time to peak effect varies from 30 minutes to 3-5 hours depending on the formulation of diclofenac taken.

7. Interactions

Medicines that interact with diclofenac may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with diclofenac. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed. Common medications that may interact with diclofenac include:

• ACE inhibitors or ARBs, such as captopril, enalapril, or losartan
• Antibiotics, such as ciprofloxacin or vancomycin
• Anticoagulants (blood thinners) such as apixaban, dabigatran, fondaparinux, heparin, or warfarin
• Antidepressants, such as citalopram, escitalopram, fluoxetine, or paroxetine
• Antifungals, such as voriconazole
• Beta-blockers, such as acebutolol, atenolol, bisoprolol, or carvedilol
• Bisphosphonates, such as alendronate
• Diuretics (water pills), such as chlorthalidone, chlorothiazide, or hydrochlorothiazide
• HIV medications (eg, Stribild, tenofovir)
• Other nonsteroidal anti-inflammatories (NSAIDs), such as celecoxib, etodolac, ibuprofen, ketorolac, meloxicam, nabumetone, or naproxen
• Sulfonylureas (a type of diabetes medication), such as glimepiride, glyburide, or glipizide
• Supplements, such as glucosamine, omega-3 fatty acids, vitamin E
• Others, such as cyclosporine, lithium, methotrexate, pemetrexed, pirfenidone, or tacrolimus.

Drinking alcohol while taking diclofenac may increase the risk of gastrointestinal-related side effects or kidney damage.

Note that this list is not all-inclusive and includes only common medications that may interact with diclofenac. You should refer to the prescribing information for diclofenac for a complete list of interactions.

References

• Diclofenac [Package Insert]. Revised 10/2023. Advagen Pharma Ltd. https://www.drugs.com/pro/diclofenac.html

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use diclofenac only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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