BMJ Group Medical Reference
This information is for adults who get migraines. It tells you about diclofenac, a treatment used for migraines. It is based on the best and most up-to-date research.
Does it work?
If you have a migraine headache, you are more likely to feel better if you take diclofenac than if you don't take any medicine at all. And diclofenac may make your headache go away completely.
What is it?
Diclofenac is a type of painkiller called a nonsteroidal anti-inflammatory drug (NSAID). It's similar to ibuprofen.
You usually take diclofenac as a tablet. The brand names are Voltarol and Diclomax. You can also get a low-dose tablet without a prescription (Voltarol Pain-eze Tablets). Studies have also looked at injections of diclofenac.
How can it help?
Diclofenac can make a migraine attack less severe and may make it go away completely. It can also shorten an attack.
Here is what the research found.
One study found that diclofenac gave headache relief to more than 3 in 10 people taking 50 milligrams (mg) and about 4 in 10 people taking 100 mg. 
Another study found that diclofenac made migraine headaches bearable or made headaches last for less than two hours in 2 in 10 to 3 in 10 people who took it. 
Of the people in the above studies who took a dummy treatment (a placebo), about 2 in 10 had the same improvement in their symptoms.  
If you take diclofenac, you are less likely to need to take other painkillers for your headache.
Diclofenac injections can reduce headache pain quite quickly. In some people they work within 35 minutes.  More than 4 in 10 people who have injections find their migraine symptoms get better within one hour. 
Diclofenac injections can also help if you have migraine with aura. One study found it relieved headaches for 5 in 10 people who had migraines with auras.  (To learn more about migraines with auras, see What are migraines?)
Diclofenac may also relieve other symptoms of an attack, such as being extra-sensitive to light or sound. It may also help you get back to your normal routine faster.
How does it work?
Like other NSAIDs, diclofenac works by stopping your body making chemicals called prostaglandins. Your body makes these chemicals when you are in pain or injured. Prostaglandins cause inflammation and make you more sensitive to pain. By stopping the prostaglandins, diclofenac can help you feel better.
Can it be harmful?
Diclofenac may increase the risk of having a stroke or heart attack. There are likely to be three extra heart attacks or strokes every year for every 1,000 people taking high daily doses of diclofenac.