about
Analgesic combinations
Short Description
Analgesics (painkillers) are drugs that relieve pain. Since pain is not a disease but a symptom, long-term relief depends on treatment of the underlying cause. For example, the pain of toothache can be relieved by drugs but can be cured only by appropriate dental treatment. If the underlying disorder is irreversible, such as some rheumatic conditions, long-term analgesic treatment may be necessary.
Damage to body tissues as a result of disease or injury is detected by nerve endings that transmit signals to the brain.
The interpretation of these sensations can be affected by the psychological state of the individual, so that pain is worsened by anxiety and fear, for example. Often a reassuring explanation of the cause of discomfort can make pain easier to bear and may even relieve it altogether.
Anti-anxiety drugs are helpful when pain is accompanied by anxiety, and some of these drugs are also used to reduce painful muscle spasms. Some antidepressant drugs act to block the transmission of impulses signalling pain and are particularly useful for nerve pains (neuralgia), which do not always respond to analgesics
Types of analgesics
Analgesics are divided into the opioids (with similar properties to drugs derived from opium, such as morphine) and non-opioids. Non-opioids include all the other analgesics, including paracetamol, nefopam, and also the non-steroidal anti-inflammatory drugs (NSAIDs), the most well known of which is aspirin. The non-opioids are all less powerful as painkillers than the opioids. Local anaesthetics are also used to relieve pain . Opioid drugs and paracetamol act directly on the brain and spinal cord to alter the perception of pain. Opioids act like the endorphins, hormones naturally produced in the brain that stop the cell-to-cell transmission of pain sensation. NSAIDs block the formation of pain-modulating substances (e.g. prostaglandins) at nerve endings at the site of pain. When pain is treated under medical supervision, it is common to start with paracetamol or an NSAID; if neither provides adequate pain relief, they may be combined. A mild opioid (for example, codeine) may also be used. If the less powerful drugs are ineffective, a strong opioid such as morphine may be given. As there is now a wide variety of oral analgesic formulations, injections are seldom necessary to control even the most severe pain.
When treating pain with an over-the- counter preparation, for example, taking paracetamol for a headache, you should seek medical advice if pain persists for longer than 48 hours, recurs, or is worse or different from previous pain.
Non-opioid analgesics
Paracetamol
This analgesic is believed to act by reducing the production of chemicals called prostaglandins in the brain. However, paracetamol does not affect prostaglandin production in the rest of the body, so it does not reduce inflammation, although it can reduce fever. Paracetamol can be used for everyday aches and pains, such as headaches, toothache, and joint pains.
As well as being the most widely used analgesic, it is one of the safest when taken correctly. It does not usually irritate the stomach and allergic reactions are rare. However, an overdose can cause severe and possibly fatal liver or kidney damage. Its toxic potential may be increased in heavy drinkers.
Non-steroidal anti-inflammatory drugs (NSAIDs)
aspirin
Used for many years to relieve pain and reduce fever, aspirin also acts to reduce inflammation by blocking the production of prostaglandins, which contribute to the swelling and pain in inflamed tissue.
Aspirin is useful for headaches, toothache, mild rheumatic pain, sore throat, and discomfort caused by feverish illnesses.
Given regularly, it can also relieve the pain and inflammation of chronic rheumatoid arthritis.
Aspirin is found in combination with other substances in a variety of medicines .
It is also used in the treatment of some blood disorders, since aspirin helps to prevent abnormal clotting of blood by preventing platelets from sticking together.
Aspirin in the form of soluble tablets, dissolved in water before being taken, is absorbed into the bloodstream more quickly, thereby relieving pain faster than tablets. Soluble aspirin is not, however, less irritating to the stomach lining. Aspirin is available in many forms, all of which have a similar effect, but because the amount of aspirin in a tablet of each type varies, it is important to read the packet for the correct dosage.
It is not recommended for children aged under 16 years because its use has been linked to Reye’s syndrome, a rare but potentially fatal liver and brain disorder. Other non-steroidal anti-inflammatory drugs (NSAIDs) These drugs can relieve both pain and inflammation. NSAIDs are related to aspirin and also work by blocking the production of prostaglandins. They are most commonly used to treat muscle and joint pain and may also be prescribed for other types of pain including period pain.
Combined analgesics
Mild opioids, such as codeine, are often found in combination preparations with non-opioids, such as paracetamol. The prefix “co-” is used to denote a drug combination. Although both opioids and paracetamol act centrally, these mixtures have the advantage of combining different mechanisms of action.
Another advantage of combining analgesics is that the reductions in dose of the components may reduce the side effects of the preparation.
Combinations can be helpful in reducing the number of tablets taken during long-term treatment.
Opioid analgesics
These drugs are related to opium, an extract of poppy seeds. They act directly on several sites in the central nervous system to block the transmission of pain signals.
Because they act directly on the parts of the brain where pain is perceived, opioids are the strongest analgesics and are therefore used to treat the pain arising from surgery, serious injury, and cancer.
These drugs are particularly valuable for relieving severe pain during terminal illnesses.
In addition, their ability to produce a state of relaxation and euphoria is often of help in relieving the stress that accompanies severe pain.
Morphine is the best known opioid analgesic. Others include diamorphine (heroin) and pethidine.
The use of these powerful opioids is strictly controlled because the euphoria produced can lead to abuse and addiction.
When these opioids are given under medical supervision to treat severe pain, the risk of addiction is negligible.
Opioid analgesics may prevent clear thought and cloud consciousness. Other possible adverse effects include nausea, vomiting, constipation, drowsiness, and depressed breathing.
When they are taken in overdose, these drugs may induce a deep coma and lead to fatal breathing difficulties.
In addition to the powerful opioids, there are some less powerful drugs in this group that are used to relieve mild to moderate pain. They include codeine and tramadol.
The opioids’ normally unwanted side effects of depressing respiration and causing constipation make them useful as cough suppressants and as antidiarrhoeal drugs.
SITES OF ACTION
Paracetamol and the opioid drugs act on the brain and spinal cord to reduce pain perception. Non-steroidal anti-inflammatory drugs (NSAIDs) act at the site of pain to prevent the stimulation of nerve endings. NSAIDS AND DIGESTIVE TRACT IRRITATION
NSAIDs can cause irritation, even ulceration and bleeding, of the stomach and duodenum, so they are best taken after a meal.
NSAIDs are not usually given to people with stomach ulcers. An NSAID may be combined with an anti-ulcer drug . In certain cases, a COX-2 inhibitor may be used.
However, NSAIDs are usually only given in the lowest effective dose for the shortest duration.
Cause of pain
Damage to tissue (due to injury or infection, for example) leads to the production of chemicals, called prostaglandins, which act on nerve endings so that a signal is passed along a series of nerve cells to the brain, where the signal is interpreted as pain by brain cells.
Action of NSAIDs
These drugs block production of prostaglandins. As a result, the nerve endings cannot be stimulated, so no pain signal passes to the brain. Action of opioids
Normally the pain signal is transmitted between brain cells. Opioids combine with receptors on brain cells (opioid receptors), blocking transmission of pain signals within the brain and also in the spinal cord.