Types of Medication
Medicines Used for Pain
This is an important area as most people living with persistent pain will either use or have used medication to try and ease their symptoms. There are a number of groups of medicines to treat pain:
- Simple analgesics (e.g. Paracetamol)
- Anti-inflammatory Drugs (e.g. Ibuprofen or Naproxen)
- Opioids (e.g. Codeine, Morphine, Fentanyl or Tramadol)
- Anti-epileptic drugs (e.g. Gabapentin or Pregabalin)
- Antidepressant drugs (e.g. Amitriptyline or Duloxetine)
- Others (uncommon ones) (e.g. Ketamine, Diazepam)
In general, no more than one medicine from each group would be used at the same time. In some situations like nerve related pain, the clinician prescribing may choose to add another medicine from the same group to try and get better pain control.
Simple Analgesics – Paracetamol
Paracetamol has been around a long time, despite this, amazingly, we don’t really understand how it works as a painkiller. There is increasing evidence that most of its action is in the brain. On it’s own, Paracetamol is quite good for mild pain. It’s also used in combination with certain other drugs (e.g.Co-codamol where it is mixed with Codeine) ; this can improve its painkilling action. Some studies have shown these combinations can be at least as effective as low doses of Morphine.
The main drawback with Paracetamol is its harmful effect if too much is taken. Our bodies get rid of Paracetamol by using chemicals made by the liver. If large amounts of Paracetamol are taken, the chemical used by the liver to break down Paracetamol can run out. While the liver is trying to make more of this chemical it uses a substitute break down chemical. This substitute chemical makes a poisonous compound which can damage the liver so badly that it won’t recover. People die each year as a result. If Paracetamol is taken in normal doses there is very little risk.
This type of medicine is the most commonly prescribed drug for pain in the world. They are good for treating mild-moderate pain. They work by stopping some of the chemicals produced by the body, which irritate nerve endings. Most of these irritating chemicals have other important uses in various places like heart, kidneys or stomach, and in healing damage to the body. For this reason there can be good and bad effects when using these medicines. Most of us will have heard about or even experienced the stomach irritation caused, but we’ve realised more about these medicines in the past ten years. Its been shown that they can also increase blood pressure and increase strokes or heart attacks in people who are at risk. GPs know this and are far more careful about who gets these type of medicines. Even when buying these medicines over the counter the comments on the packaging suggest if symptoms don’t settle then it’s best to discuss with your doctor. He or she can then assess whether you are at risk of problems and if you need a different way to manage your pain.
These medicines have been around for over three thousand years. They are usually thought of as either weak or strong (see some examples below).
|Weak Opioids||Strong Opioids|
Usually weak opioids are taken for mild pain. Codeine is often taken with Paracetamol which can improve its pain relief. Codeine is actually changed by the liver into small doses of morphine, which gives its effect. About one in ten people in the UK can’t change Codeine in this way (because they don’t have the chemical necessary in the liver), so Codeine does not work for them.
Strong opioids are used to treat moderate to severe pain. Up until fairly recently this was either resulting from surgery, injury or cancer, but now strong opioids are increasingly being used to treat chronic pain. The most common strong opioid is Morphine, which is found in some types of poppy plant. The plant is collected, refined and made into medicine. Most of the other strong opioids are either a variation of morphine (semi-synthetic) or made from scratch (fully synthetic). This is important as they behave differently in the body depending on how they are made. Some can be put into a patch (which gradually dissolves the drug through the skin), and some need to be taken by mouth or injection.
Opioids work in the brain and spinal cord by reducing the amount of pain signals sent up into the brain. To do this they must pass into the brain. Any substance that does pass into the brain can cause unwanted or unpleasant effects. Opioids commonly do this, with side effects like nausea, dizziness, drowsiness. These side effects usually improve over days or weeks but occasionally they do not. Other unwanted effects like constipation are also common – this does not improve with time and usually requires another medicine with the opioid to stop it from happening. In the last few years there has been some research suggesting using opioids for a long time use can disturb hormones in the body (reduced testosterone in men and reduced oestrogen in women, affecting fertility). This is obviously a concern and research is ongoing.
Opioid drugs need careful attention when starting. Getting to the right dose can take several weeks, and may need to be done gradually. This is also true for stopping opioids which need to be tailed off and not stopped suddenly. This is because the body naturally produces its own supply of opioid chemicals (called endorphins and encephalins). If these chemicals are added to by opioid drugs from tablets etc, the body drastically cuts down how much opioid chemicals it makes. If the tablet supply is suddenly stopped, then the body has hardly any opioid, which feels very unpleasant (‘cold turkey’). It can take several days for the body to catch up making the right amount of its own opioid.
There is often worry about getting addicted to strong opioids. Most of this worry is not necessary. In the published research studies there is very little evidence that opioids taken for a pain problem cause addiction. It is easy to become dependent upon opioids in a similar way to someone with asthma may become dependent upon their inhalers.
This type of medicine is used usually to treat pain from nerves that don’t work properly (in chronic pain it is the pain nerves that don’t work properly). It does not mean that you have epilepsy or are at risk of getting it. These drugs work by stopping the sensitivity of the brain and spinal cord. The best way to think of this is by imagining toilets (yes really!). Some old toilets need a good pull on the handle to flush, but some are very sensitive and only need a light touch to flush. Our nerves are a bit like this. The pain nerves especially in our brain and spinal cord can be very sensitive, especially if they have been damaged or irritated by inflammation. Sometimes this can happen by having pain for a long time. Small movements can be very painful which can partly be because of increasing sensitivity. People with pain from Shingles understand this very well because the lightest of touches on the skin can be agonising. By using anti-epileptic drugs, the pain nerves can be made less sensitive, so they need a much stronger stimulus to make them fire off. This can reduce pain intensity.
Like opioid drugs, anti-epileptic drugs need to get into our brain to work. when they do this, they can also give us unwanted effects similar to the ones above (nausea, dizziness, drowsiness etc). to try and stop this from happening, starting and stopping these medicines needs to be done gently over weeks.
Common examples of this type of medication are Gabapentin or Pregabalin.
These medicines have been around a long time. In the last twenty years a new generation of anti-depressants have been developed which are much safer and have less unwanted effects. Like some of the other medicines above, anti-depressants need to get into the brain to work, and can cause similar unpleasant effects. Again these effects can be reduced by starting slowly at first, or by tailing off slowly and not stopping the medicine quickly.
Antidepressants can improve pain by increasing some of the chemicals in our brain and spinal cord. This can have the effect of turning down the loudness on pain (a bit like a volume control on a stereo)
Often people with pain will say ‘I’m not depressed – I’m in pain’. We do know from lots of good research studies that some of the control over pain that our brains have is not as good if we are depressed or anxious. It’s like the volume control we mentioned gets stuck. If our mood can improve (with medicines, relaxation, or other types of non-drug treatment) we can get the volume control turned back down again.
A common example of anti-depressant medication used for treating persistent pain is Amitriptyline.
However amitriptyline is also commonly used for nerve (neuropathic) pain where patients do not have anxiety or depression.