Pain relief: How NSAIDs work

NSAIDs - or nonsteroidal anti-inflammatory drugs - are among the most common pain relief medicines in the world, taken to soothe headaches, sprains, arthritis symptoms and other daily discomforts. In addition to dulling pain, NSAIDs also lower fever and reduce swelling.

But how do those little pills do so much? And if they're so good in some ways, why do they also raise the risk of heart problems in some people? The answer is complicated. Even researchers don't fully understand how NSAIDs work.

Nonetheless, with the benefits and risks of NSAIDs frequently in the headlines, We turned to four experts to explain what researchers do know. Our panel consisted of:

• Professor Justin Mason of Imperial College, London and spokesman for the UK’s Arthritis Research Campaign.
• Dr Byron Cryer, a spokesperson for the American Gastroenterological Association.
• Dr Nieca Goldberg, a spokesperson for the American Heart Association.
• Dr John Klippel, president of the Arthritis Foundation in the US.
• Dr Scott Zashin, clinical assistant professor at the University of Texas Southwestern Medical Center in Dallas, Texas, in the US, and author of Arthritis Without Pain.

Here is their explanation of how NSAIDs help ease your pain - and sometimes cause side effects in the process.

What is pain?

First it helps to understand what pain is. On a basic level pain is the result of an electrical signal being sent from your nerves to your brain.

But the process is not only electrical. When you get injured - say with a sprain - the damaged tissue releases chemicals called prostaglandins, which are like hormones. These prostaglandins cause the tissue to swell. They also amplify the electrical signal coming from the nerves. Basically they increase the pain you feel.

How do NSAIDs help relieve pain?

NSAIDs work on a chemical level. They block the effects of special enzymes - specifically COX-1 and COX-2 enzymes. These enzymes play a key role in making prostaglandins. By blocking the COX enzymes, NSAIDs stop your body from making as many prostaglandins. This means less swelling and less pain.

Most NSAIDs block both COX-1 and COX-2 enzymes. They include the over-the-counter drugs aspirin and ibuprofen.

Other NSAIDs are available by prescription. They include:

• diclofenac
• ketoprofen
• naproxen
• etodolac

Aspirin has some benefits that other NSAIDs do not. The main one is that aspirin works against the formation of blood clots. As a result you are less likely to form the clots that can cause heart attacks and strokes. Other NSAIDs do not have this effect.

COX-2 inhibitors are a newer form of prescription NSAID. As you might guess, they only affect COX-2 enzymes and not COX-1.

What are the side effects from standard NSAIDs?

Most people who use NSAIDs don't have any serious problems with them. But for some people - especially those who need pain relief regularly - there can be problems.