Diclofenac

Key facts

• Diclofenac (found in Voltaren and many generic tablets, gels and patches) is a non-steroidal anti-inflammatory drug (NSAID). It blocks pain and swelling by reducing prostaglandins, chemicals that drive inflammation.
• Oral diclofenac is usually taken with food to protect the stomach; topical gels are applied directly to the painful joint or muscle.
• Like all NSAIDs, diclofenac raises the risk of heart attack and stroke, and can cause serious, sometimes fatal, stomach bleeding or ulcers. Both risks grow with higher doses and longer use.
• Seek urgent care for chest pain, sudden weakness on one side of the body, black or bloody stools, or vomit that looks like coffee grounds.

What diclofenac treats

Diclofenac relieves pain and inflammation from osteoarthritis, rheumatoid arthritis and ankylosing spondylitis. It is also used for acute pain after an injury or surgery, migraine attacks, menstrual cramps, and gout flares. Topical gels target localized joint pain, such as in the knee or hand, with less effect on the rest of the body than tablets.

How diclofenac works

Injured or inflamed tissue produces prostaglandins, chemicals that sensitize nerve endings and widen blood vessels, causing pain, heat and swelling. Diclofenac blocks the cyclooxygenase (COX) enzymes that make prostaglandins, so less of the chemical is produced and the pain and swelling ease.

Before you take it

• Do not take diclofenac if you have had an allergic reaction (including asthma, hives or swelling) to aspirin or another NSAID, or if you are in the third trimester of pregnancy.
• Tell your prescriber about heart disease, high blood pressure, stroke, kidney or liver disease, stomach ulcers, or asthma. These raise the risk of serious side effects.
• Combining diclofenac with other NSAIDs, aspirin, blood thinners, corticosteroids, or regular alcohol use increases the risk of stomach bleeding.
• Avoid diclofenac around the time of heart bypass surgery.

Side effects

Common effects include stomach upset, heartburn, headache, dizziness and, with gels, mild skin irritation at the application site.

Stop and seek urgent medical care for any of these:

• Chest pain, sudden shortness of breath, or weakness on one side of the body.
• Vomiting blood or material that looks like coffee grounds, or black, tarry stools.
• Swelling of the face, lips or tongue, or difficulty breathing.
• Yellowing of the skin or eyes, or unusual bruising.

Safety essentials

• Diclofenac carries a boxed warning for increased risk of heart attack and stroke, which can occur even in the first weeks of use and rises with dose and duration. Use the lowest effective dose for the shortest time needed.
• It can cause stomach or intestinal bleeding at any time during treatment, often without warning symptoms; older adults and people with a past ulcer are at higher risk.
• Take the lowest dose that controls your symptoms, and tell your pharmacist about every other medicine you take, since combining NSAIDs multiplies the bleeding risk.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.