Pain Centre

29 November 2011

The different groups of painkillers

Here follow details of different types of painkillers.

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Painkillers (analgesics) can generally be classified in three main categories:

1. Paracetamol
Panado and Tylenol are well-known brand names. One of the main attractions of paracetamol is that it has few side effects. This does not mean that paracetamol can be taken with impunity, because there are possible side effects and these can be devastating! One is liver failure, especially when paracetamol is taken on a long-term basis, in too high quantities, or in combination with acute or chronic alcohol abuse. One of our university hospitals recently admitted a 42-year-old migraine sufferer who used paracetamol on a regular basis, and who had then taken 2 grams (four tablets) of paracetamol with a glass of port wine. Three days later she died from liver failure.

 2. Aspirin and NSAIDs (non-steroidal anti-inflammatory drugs)
This group of drugs is effective against mild to moderate pain, and against fever and inflammation. They are therefore widely used for dental pain, dysmenorrhoea (painful menstruation), headache, bone pain, trauma, arthritis, and many more indications.

“Non-steroidal” means that they are not steroids (i.e. they do not belong to the “cortisone” family). Steroids are very effective against inflammation, and the term NSAID is used to differentiate this group of drugs from the actual steroid family.

“Anti-inflammatory” means that they are effective against inflammation. Some are better against pain and some better against inflammation, so your doctor will choose the product according to your individual needs. Also, different people react differently, so that one product might work well for one person, but may not be as effective in another person.

Aspirin: Disprin and Codis are well-known brand names. It is widely used as a painkiller, and even more widely and effectively (in low dosages) for its blood-thinning side effects, lowering the risk of heart disease. People should not exceed the maximum prescribed dosage, especially not over a long period of time, as prolonged use of high dosages is associated with an increased risk of stomach ulcers.

Aspirin is also an antipyretic and widely used to fight fever. This is one of the best researched medications of our time, and evidence of various positive side effects such as a preventative role in cancers of the pancreas, colon and prostate is now emerging. The long-term prophylactic use of this drug in low dosages to prevent heart disease and other illnesses makes it one the most widely used drugs in the world.

NSAIDs include diclofenac (Voltaren) and ibuprofen (Brufen). These medications are especially effective for musculo-skeletal pain. If you are feeling stiff or you are experiencing body pain after an operation or after exercise, or if your joints are arthritic and painful, these are the most effective painkillers. The combination of these medications with paracetamol often seems to be most effective. NSAIDs should never be combined with other NSAIDs, including aspirin. Doing this would increase the risk for side effects without increasing the efficacy of the medication. The most common side-effects of these drugs are stomach ulcers.

3. Opioids
The opioids work on specific opioid receptors in the body, which are mainly located in the brain and the spinal cord. Many oral opioids are used in the treatment of chronic pain. Combining opioids with other painkillers such as paracetamol and NSAIDs involves attacking the pain on different receptors. This often decreases your opioid requirements by up to 30%, which leads to improved pain relief and a reduced risk of side effects.

Well-known examples of opioids are codeine, morphine and pethidine.

They can be categorised according to their effect as:

Low-efficacy opioids examples include codeine (codeine phosphate).They are effective against mild to moderate pain, but scientific studies have shown that paracetamol and NSAIDs in optimal doses are more effective. If paracetamol with or without an NSAID does not relieve your pain sufficiently, you will benefit by adding codeine to your medication. Many manufacturers combine these different painkillers in one commercial preparation and aim to block pain at two or three different receptor sites with one tablet (e.g. Myprodol : paracetamol + ibuprofen + codeine; Doxyfene : paracetamol). Like all the opioids, codeine and propoxyphene might cause sedation. Codeine is also a good cough suppressant, even at lower doses than used for pain relief.

Moderate-efficacy opioids

These include dihydrocodeine (e.g. DF118®), tilidine (DF118n®) and tramadol (Tramal®). They are effective against moderate pain, and in adequate doses also against more severe pain. They can be taken orally. Tramadol causes less sedation and respiratory depression. None of these agents should be taken together with other central nervous system depressants like sleeping tablets, sedatives, or even alcohol.

High-efficacy opioids

Examples of strong opioids are morphine and pethidine. They are effective against severe pain and are mostly administered by injection. An interesting finding after surgery is that strong opioids do not seem to take ordinary headaches away, whereas simple paracetamol does.

The side effects differ in severity between the different preparations, but generally affect one’s mental state: drowsiness, decreased alertness (take care when driving a car), sedation (or sometimes agitation, especially in children), euphoria or dysphoria (e.g. some patients report that it feels as if their body does not belong to them anymore), dependence and addiction. Respiratory side effects can include depression of breathing and cough; extreme caution is warranted if you have asthma or chronic obstructive lung disease. Other side effects could be nausea and vomiting, constipation (never take opioids together with anti-diarrhoeal drugs), constriction of the gall-bladder sphincter (it can make a gallbladder crisis worse), difficulty in passing urine and itching. If you take opioids for a long time, the effects could fade.

Different opioids should not be combined, as this increases the risk for possible side effects without increasing the efficacy of the medication.The codeine levels in combination-type medications that contain codeine are quite low, and may even be too low to relieve pain, but high enough to cause drowsiness.

Local anaesthetics, nerve blocks and epidurals
Local anaesthetics (including nerve blocks) and epidurals can also be used for pain relief. Local anaesthetics include lignocaine, bupivacaine and ropivacaine.

Reviewed by Prof CL Odendal, senior specialist at the department of anaesthesiology at the University of the Free State, April 2010.

Read more:
Can I get out of bed?
No need to feel cut up

Links:
Arthritis Foundation of South Africa
Multiple Sclerosis South Africa
The South African Society of Physiotherapy

 

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Pain expert

Dr Raath originally specialised and worked as an anaesthesiologist in private practice. In 2008 he obtained his Fellowship In Interventional Pain Practice and since then has operated the the Pain Clinic at the Netcare Jakaranda Hospital in Pretoria which treats all forms of chronic pain. Read more here.

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