How does morphine work to kill pain?

26 June 2011

Question

How is morphine is a painkiller? Since I smashed my ankle the pain is terrible. I have been put on oral morphine.
Thank you.......... Adrian

Answer

Morphine is one of the most famous painkillers. It's an opioid drug, which means it's a cousin of the ancient drug opium, which has been used socially and in medicine thousands of years.

These drugs bind to the opioid receptors, which are on the surfaces of nerve cells in the brain and spinal cord. This sets off a chain of chemical signals within the cell which ultimately cause the cell membrane to become less excitable. This means that pain-sensing nerve cells become electrically "sluggish" and don't fire so many impulses.

As well as dulling pain by silencing nerves in the spine that carry pain signals, morphine also has complex effects in the pain processing areas in the brain, including suppressing the action of the nerve pathways that control breathing, heart rate and blood pressure. This is why an overdose of morphine is so dangerous, because it can trigger a person to stop breathing, which is called a respiratory arrest.

Morphine receptors are also found on nerves all over the body. To cite on example, the nerves that supply the muscles in the gut are slowed down by morphine; this can cause severe constipation, which patients taking opioid drugs need to be made aware of.

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