What are Non-steroidal Anti-inflammatory Drugs?
Action and Side-effects of These Pain Killers
Apr 22, 2009
Non-steroidal anti-inflammatory drugs (NSAIDs) are in wide use. Although most commonly used for musculo-skeletal complaints like back pain and arthritis they are bought and prescribed for many pain conditions.
In addition to their pain killing effect they also, as the name suggests, have an anti-inflammatory action – this is what makes them so useful in arthritis where much of the pain is generated by inflammation in the joint. They also help reduce fever. Although usually not thought of as such aspirin is a NSAID but less effective and with more side-effects. Paracetamol, the other common pain killer reduces fever but not inflammation.
Action of Non-steroidal Anti-inflammatory Drugs
The reason NSAIDs have several beneficial effects is due to a class of compounds produced by the body called prostaglandins. These are are mainly involved in providing protection for various body tissues. Different prostaglandins do this in different ways but a particular group encourages the inflammatory response and sensitizes nerve endings to enhance pain sensation. Believe it or not this is a protective action: inflammation although unpleasant is important in protecting against infection and pain of course alerts us to an injury.
Prostaglandins in the brain are partly responsible for setting the body's thermostat. Certain infections will cause these compounds to set this thermostat higher and hence produce fever. This is thought to help fight off the infection.
NSAIDs interfere with the production of prostaglandins by inhibiting enzymes called cyclooxygenases. Two are of relevance here and are abbreviated to COX1 and COX2. By limiting prostaglandin production NSAIDs limit inflammation and pain sensation and keep fever down.
Side Effects of Non-steroidal Anti-inflammatory Drugs
Unsurprisingly these relate to prostaglandins. In addition to the above actions these compounds have effects elsewhere. It is interference with their protective effect in these areas that causes the side effects. The occurrence of side effects varies greatly from person to person and according to the type of NSAID being used.
- Stomach problems: prostaglandins help the stomach produce protective mucus and reduce acid secretion. Inhibition of these compounds can bring about ulcers and stomach bleeding.
- Clotting problems: two of the factors involved in blood clotting are prostaglandins, for this reason people on anticoagulants and those with clotting defects are advised not to take NSAIDs.
- Asthma: NSAIDs can exacerbate asthma. Prostaglandins help regulate mucus production and muscle tone in the airways therefore asthmatics are advised to seek medical advice before taking NSAIDs.
- Kidney problems: Prostaglandins may have a protective effect on the kidney so NSAID treatment can have an adverse effect on this organ.
The Newer Anti-inflammatory Drugs
The COX1 and COX 2 enzymes produce different types of prostaglandin. COX1 helps synthesize prostaglandins that produce the protective stomach mucus whereas COX2 is involved with sensitizing pain receptors.
The older NSAIDs, like ibruprofen are non-specific and inhibit both types of COX. The more recently developed drugs are more specific for COX 2 therefore these are less likely to interfere with stomach mucus production and cause ulcers.
This article is for information only. If you have any health concerns you should consult your doctor.
Resources
Pills Potions Poisons by Stone and Darlington. Pub. Oxford University Press 2000
British National Formulary 2008. Pub. British Medical Association
 |
