How are medicines used? Analgesics

Currently the World Health Organisation (WHO) suggests that analgesics are used in a series of three steps depending on the level of pain. Pain levels are rated from 0 (no pain) to 10 (worst pain ever).

WHO STEP ONE:

For mild pain level (less than 4):

Non-opioid analgesics, e.g. paracetamol or aspirin

Anti-inflammatories, e.g. ibuprofen or diclofenac

WHO STEP TWO:

For moderate pain level (4–7):

Weak opioid drugs, e.g.

Codeine phosphate (doses vary, e.g. 15 mg, 30 mg, 60 mg)

Codydramol=Paracetamol 500 mg+dihydrocodeine 10 mg

Co-Codamol=Paracetamol 500 mg+codeine 8 mg or 30 mg

Dihydrocodeine 30 mg or slow-release forms

Tramadol 50–100 mg or slow-release forms

WHO STEP THREE:

Severe pain level (7–10):

Strong opioid drugs, e.g. Morphine, which can be taken in different ways, such as liquid oral morphine sulphate, or in long-acting preparations like MST (doses vary, e.g. 10 mg, 30 mg, 60 mg, 100 mg), or even as suppositories.

Buprenorphine, oxycodone and fentanyl are other opioid drugs that can be taken for severe pain.

All these opioid drugs can cause dependence.

Problems with medicines

WHY DON’T MEDICINES ALWAYS REDUCE CHRONIC PAIN?

Deciding which analgesic to use for pain can be a difficult process of trial and error. Doctors often start with mild analgesics, such as paracetamol or co-codamol, and may try to match the pain level with the right type and dose of a drug.

Analgesics work well for acute pain problems, where there is an injury or inflammation, like a sprained wrist or a headache. They also relieve the pain in heart attacks, fractures, after operations, and in burns and inflammations such as throat infections.

However, people with chronic pain often find that analgesics are not very useful in reducing their pain. This is because the chronic pain system works very differently from the acute pain system (see Chapter 2). These are some of the problems that can occur in the chronic pain system:

•   When the pain system is on ‘high alert’, the pain receptors in the pain areas act like over-sensitive burglar alarm sensors. They may set off the ‘alarm’ even when there is no ‘burglar’.

•   The pain nerves (called C fibres) that take signals to and from the pain site in the body to the pain centres in the brain, are sometimes faulty. The effect is rather like what happens when all the traffic lights are faulty and out of sequence at a busy crossroads.

•   The pain centres in the brain try to make sense of all the different types of signals coming from many areas in the body and the brain. Sometimes they become confused and give out a ‘pain alert’ when it is not needed. So again an alarm is set off when there is no ‘burglar’.

These difficulties in the pain system seem to cause and maintain pain themselves. Other factors, such as being depressed or anxious, being unfit, or being tense and under strain, also contribute to chronic pain. Researchers are trying to understand these chronic pain system difficulties better, in order to find better ways to relieve this type of pain in the future.

WHAT IS TOLERANCE?

People may develop tolerance to many medicines, including analgesics, when they take them for many weeks or months. Tolerance means that the medicine becomes less effective at reducing the pain over time (usually a matter of weeks). The dose of the medicine has to be increased in order to get the same amount of pain reduction. This leads to bigger doses of the medicine being taken and many more side-effects.

WHAT IS DEPENDENCE?

Medicine dependence means addiction, and it mainly happens when medicines are misused. For instance, people might take increasing doses without assessing whether they are really reducing their pain levels. Dependence can occur within a few days or weeks of use. And people may get withdrawal symptoms, such as a dry mouth, shaking, itching and feeling sick, when they reduce or stop the medication.

WHAT ARE THE SIDE-EFFECTS OF MEDICINES?

All medicines have side-effects. Here are the most common ones:

•   Dependency

•   Constipation

•   Nausea and vomiting

•   Indigestion

•   Dry mouth

•   Dizziness

•   Tiredness

•   Poor concentration

•   Mood changes or mood swings, e.g. depression, feeling anxious

•   Poor memory, forgetful

•   Feeling of detachment – ‘not really with it’

•   Hallucinations

•   Dreams/nightmares

Any others? (List them in your notebook.)

HOW DO MEDICINES REACT WITH OTHER MEDICINES?

Medicinies can have effects on other medicines and the way they work in the body. This is called a drug interaction and it can happen with any of the medicines taken for pain. For instance:

•   Tramadol and amitriptyline, or other anti-depressants, can increase drowsiness.

•   Different analgesics can change the effect of carbamazepine. Some reduce its effect and others increase it.

•   Some pain-relief medicines will affect medicines used for other conditions such as heart disease.

It is important to check with your doctor, pain specialist or pharmacist whether your medicines interact or can have an antagonistic effect with each other.

WHAT ABOUT ALLERGIC REACTIONS TO MEDICINES?

Some people are allergic to certain medicines and may experience additional problems, such as rashes, fevers and other symptoms. It’s hard to predict who is going to have an allergic reaction to a pain-relief medicine but it is more likely to happen in people who have allergies to other medicines. If you are concerned about this problem, talk to your doctor.