There is a bewildering variety of painkillers on the market,
some available over the counter, and others strictly controlled. Most are
effective to some degree, but you should be aware of possible side-effects.
Pain is a symptom, not a disease. In the long term, freedom from pain depends
on treating the underlying cause where possible. In the short term, though,
several drugs bring some relief from pain. Some are available over the counter
and others on doctor's prescription only.
Pain is experienced when injury or illness causes cells to produce chemicals
called prostaglandins. These stimulate nearby nerve endings, sending signals to
the brain that are experienced as pain. Pain-killing drugs all work by
interrupting the communication between the site of the pain and the 'receivers'
in the brain.
There are two main types. Peripheral painkillers, which work by cutting down
the production of prostaglandins, include aspirin, paracetamol (which reduces
prostaglandin production in the central nervous system rather than at the origin
of the pain) and ibuprofen which, like aspirin, also relieves stiffness and
inflammation. As well as being analgesic (pain-killing) drugs, aspirin and
paracetamol are also anti-pyretic - that is, they can reduce fever.
The other type of painkillers, narcotics, operate directly on the central
nervous system. Generally more powerful in their effects, they are strictly
controlled in most countries. They include synthetic painkillers such as
distalgesic and all the opiates.
Natural opiates are derived from substances in the seed-head of the opium poppy,
and include codeine, morphine and diamorphine (heroin). The brain manufactures
and releases its own painkillers, endorphins, when the body is put under stress.
Opiates mimic these, attaching themselves to receptors in the nerve cells and
blocking the path of the pain signal between cells in the brain and in the
spinal cord. Synthetic opiates, such as pethidine, work in the same way.
As a rule, peripheral painkillers are best for relieving mild to moderate
pain in muscles or joints, headache, toothache and period pains. They can be
used fairly regularly without causing tolerance and dependence, so are useful in
relieving chronic, low-level pain, though there are some cases where they should
not be used.
Aspirin can cause breathing problems or rashes in a few people sensitive to it.
It may irritate the stomach, even causing ulcers and bleeding. Because of this
it is best taken after meals. Aspirin dissolved in water is faster acting, but
can still affect the stomach lining.
Paracetamol has none of the gastric side-effects of aspirin when taken in the
proper dosage. However, even fairly small overdoses of paracetamol can cause
serious damage to the liver and kidneys.
Although central nervous system painkillers are more powerful - an injection
of an opiate can relieve pain in seconds - their possible side-effects mean they
are generally reserved for cases of severe pain caused by surgery, serious
injury or acute illness. Side-effects include slowed breathing, nausea,
vomiting, constipation (morphine syrup mixed with kaolin is a traditional remedy
for diarrhoea) and addiction.