Science Questions

How does morphine work to kill pain?

Sat, 25th Jun 2011

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Adrian Lisecki asked:

How is Morphine is a painkiller?

Since I smashed my ankle the pain is terrible, I have been put back on

oral morphine.


Thank you.......... Adrian


Morphine is one of the most famous painkillers. Itís an opioid drug which means itís 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 surface of nerve cells and that sets off a chain of chemical reactions inside the cell which ultimately causes the cell membrane to be less excitable. this means that nerve cells become sluggish and don't fire so many impulses.  Morphine can dull pain by silencing nerves in the spine that carry pain signals, but it also has complex effects in the pain processing areas in the brain and morphine receptors are found on nerves all over the body.  So the problem is that putting a damper on all of these nerves can do more than just kill the pain.  So if you take one example, the nerves that supplied the muscles in the gut are slowed down by morphine, causing constipation and then all the other side effects are due to sluggish nerves basically.


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Morphine works by blocking the morphine receptors in the central nervous system. I've never seen it not work in acute trauma unless in renal colic (kidney stones)--and I've seen a whole lot of acute trauma.

But I get the impression your injury is not recent. I would ask your doctor to rule out the possibility that you may have developed "Reflex Sympathetic Dystrophy" (aka "causalgia" or "Complex Regional Pain Syndrome") which is a horse of a different color.

RSD requires a number of treatment modalities and morphine isn't a first line choice for it. Response to treatment varies widely -- you may have to bear this cross for some time but there is better help than just morphine alone.

Here is the National Institutes off Health page (you might want to follow up on the clinical trials link down at the bottom).

Good luck    MartinTheK, Sun, 12th Sep 2010

Surely morphine works by mimicking the action of natural endorphins. The exogenous opiate family of drugs do not block the action of natural endogenous factor - they act on the same opioid receptors as natural painkillers act.  This almost perfect mimicking of a natural action is why morphine is the standard against which other painkillers are judged.  If you are in sufficient pain for morphine to be prescribed I am really sorry for you and hope your problem is not going to be long term. 

Natural endorphins also give feelings of euphoria, relaxation, and sedation; as well as the analgesic effects.  You can easily see why such a close artificial mimic is used both as a narcotic as well as pharmocological/medicinal drug.

Get well soon!

All the best imatfaal, Mon, 13th Sep 2010

Actually different morphine analogs have differing strengths as analgesics. There are analogs which are as much as 12,000 times as "strong" as morphine sulfate. Those agents would not be 12,000 times as good at stopping pain- it's just that 12,000 times smaller dose would have a similar effect as a quarter grain (15 mg.) dose of morphine sulfate.

My previous remarks on pain relief presupposed that you have good functional recovery of your ankle and have a functional joint. You may want to seek a second orthopedic opinion before you make opiate analgesics a part of your life. MartinTheK, Mon, 13th Sep 2010

its wierd being lectured on morphine by someone who has no clue how it works.  imatfaal, Tue, 14th Sep 2010

Dang! You little old British people's conception of manners is so damned cute. Have we met or are you just naturally like that?

Let's look at the FDA package insert for MSO4, pharmacology section Mr.Smarty Pants...

"The precise mechanism of the analgesic action is unknown. However, specific CNS opiate receptors for endogenous compounds with opioid-like activity have been identified throughout the brain and spinal cord and are likely to play a role in the expression of analgesic effects."

So neither of us really knows. My explanation was appropriate for a layman. I'm not here to show people just how smart I am, but to help them, you see. But you go ahead and dazzle us with the shining beacon of all your book learning.

Say, I've got an idea! If you ever need Morphine why don't you tell your doctor that you're going to use your "natural endorphins". I would be very interested to see that.

MartinTheK, Tue, 14th Sep 2010

A couple of points.
Your attitude to nationalistic ranting has been noted several times before.
This isn't the place for it.

It is hypothesised that the analgesic effects of placebos and of hypnosis are due to endorphins; they are, as you say, very interetsing.
Bored chemist, Tue, 14th Sep 2010

It is indeed unfortunate that this Gentleman's simple request for help with his affliction can't be addressed without a load of nonsense from kibitzers with a secondary agenda popping in to show off their useless and pointless knowledge .

Your suggestion for hypnosis and placebos is really fascinating! The next time I have to work with a patient's chronic, disabling pain I will be sure to recommend the nearest guru right after he gets back from the curandero.

MartinTheK, Tue, 14th Sep 2010


I'm sure you realize that TNS cannot tolerate attacks on the gender, ethnicity or nationality of other members. Peppercorn already gave you a gentle reminder. This is not a gentle reminder, it's a public warning.

If you are more interested in testing our limits than contributing anything useful to this forum, just let me know and I'll take the appropriate action. If you want to maintain your membership so that you can contribute to this forum, please at least try to control your outbursts.
Geezer, Tue, 14th Sep 2010

Martin, you are clutching at straws and being unnecessarily abusive.  You are commenting on multiple areas which are demonstrably beyond your knowledge and flaming anyone who dares to offer a contrary opinion.  The fact that you offer a clinical opinion at the same time as typing arrant nonsense is particularly galling. 

Before replying and criticising my posts further please look up morphine in any decent science dictionary or encyclopaedia. Your response to the questioner was wrong.

imatfaal, Tue, 14th Sep 2010

The nonsense was yours.
You said that morphine acts as an antagonist at the receptor; it's an agonist.

You then went on, without benefit of any real information, to make a provisional diagnosis.
That's never a good thing; no competent doctor would diagnose a specific condition on the basis of "Since I smashed my ankle the pain is terrible, I have been put back on
oral morphine."
Also, no diagnosis was sought. It's fair to assume that the guy is in contact with a doctor who can do that.

I forgot to ask this morning; what sort of "secondary agenda" do you think we have?

I just looked up the meaning of kibitzer; it means someone who offers meddlesome unwanted advice.
Does that include one who offers a diagnosis where none was wanted and advice that's simply flat wrong?
Martin, you seem to have mistaken us for your own reflection. Bored chemist, Wed, 15th Sep 2010

Morphine is indeed an agonist-it binds and activates MORs which is turn affect the inhibition of GABA.
GABA is an inhibitory neurotransmitter that can down regulate neuronal activity, and decrease firing, ergo decreasing pain.

What is actually not known, is if morphine precisely mimics the binding of endorphins.

Variola, Wed, 15th Sep 2010

Adrian Lisecki asked the Naked Scientists: How is Morphine is a painkiller? Since I smashed my ankle the pain is terrible, I have been put back on oral morphine. Thank you.......... Adrian What do you think? Adrian Lisecki, Mon, 27th Jun 2011

British people talk in an intelligent way because they know other Brits will understand them and expect them to be generous enough not to simplify things. It is not our fault if people from other countries think we are condescending when actually we are only assuming people will be intelligent enough to understand us. Sorry if that sounded a little condescending. Relative, Fri, 8th Mar 2013

Opioids look like chemicals in your brain and body that attach to tiny parts on nerve cells called opioid receptors. Scientists have found three types of opioid receptors: mu, delta, and kappa (named after letters in the Greek alphabet). Each of these receptors plays a different role. For example, mu receptors are responsible for opioidsí pleasurable effects and their ability to relieve pain. Opioids act on many places in the brain and nervous system, including: the limbic system, which controls emotions. Here, opioids can create feelings of pleasure, relaxation, and contentment. the brainstem, which controls things your body does automatically, like breathing. Here, opioids can slow breathing, stop coughing, and reduce feelings of pain. the spinal cord, which receives sensations from the body before sending them to the brain. Here too, opioids decrease feelings of pain, even after serious injuries. brianjones978, Sat, 15th Nov 2014

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