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How does morphine work?

Morphine is used in medicine for sedating patients with acute, or chronic conditions. The milky substance found in the seedpod of the poppy plant is the natural source of morphine. When dried, it is used for making opium, which contains morphine, together with other alkaloids. But how does morphine work, exactly? We review here and invite your questions about morphine at the end.

How does morphine work in the body?

In general, the use of morphine results in relief from physical pain. But morphine can also arouse the cough reflex and give the feeling of constant hunger. After administration is absorbed into the blood and morphine stays in the body and is delivered to all its organs.  Many people don’t know that there is lower concentration of morphine in the brain and muscles compared to the kidneys, lung and liver. And a small portion goes directly to the milk of nursing women.

How does morphine affect the brain and nervous system?

The biggest effects of taking morphine take place in the receptors of the nervous system. Different branches of receptors (m, k and d) are involved in various actions, urges, and processes on a molecular level.

m 1-receptors are involved in:

  • analgesia
  • euphoria
  • decreased gastrointestinal activity
  • miosis
  • pain modulation
  • respiratory depression

m 2-receptors are involved in:

  • drowsiness
  • mental clouding
  • nausea
  • respiratory depression

k-receptors are involved in:

  • analgesia
  • diuresis
  • dysphoria
  • mild respiratory depression
  • miosis
  • sedation

d-receptors are involved in:

  • analgesia
  • delusions
  • dysphoria
  • hallucinations

How fast or quickly does morphine work?

There are many ways to take morphine, such as oral, intravenous or rectal. And the speed at which morphine works depends on the dose and the route of administration. For example, morphine injection has nearly instantaneous effect. But in, general, it could take from 15 to 60 minutes for the effects of morphine to manifest.

How long does morphine work?

Morphine actually has a short half life of 1.5 to 7 hours, except for patients who are renally impaired. (who can feel the drug effects longer than usual). Effects of narcosis and analgesia (loss of sense of pain and not loosing consciousness) can last longer for older patients.

One of the measurable effects of morphine use is gastric activities, especially constipation. In this way, morphine works to hold on to food forlonger than 12 hours, while the absorption of other orally administered drugs is totally disabled. Additionally, the normal sensitivity of the respiratory system is stabilized within 2 to 3 hours after morphine use, but the capacity of the air volume remains unstable for up to 5 hours.

How does morphine work better?

Morphine is available in several prescribed forms, such as injections, oral solutions, tablets and capsules etc. Since it is considered to be a strong painkiller, often users take bigger doses of morphine than prescribed. While there is no strict upper limit to morphine that is safe, an oral dose of 0.3g to 0.4g or morphine can be lethal.

Does morphine work for everyone?

Yes, morphine can work for everyone as a sedative and pain reliever. However, it works for everyone differently, depending on a few factors. One factor is dosage, which will be different for each individual. For example, someone who is opioid tolerant, can take higher doses of morphine than an opioid naive person.Other factors are the route of administration, previous exposure to morphine and development of signs of addiction to morphine. Once a patient is tolerant to one opiate, s/he develops tolerance to other opiates and opioids.

Morphine use questions

Do you still have questions about using morphine or how morphine works? Please leave your questions or comments in the section below. We do our best to respond to you personally and promptly.

Reference Sources: Medline Plus: Oral Morphine
PUBCHEM: Morphine
Prosecuting Attorney Institute: Morphine drug data sheet

Photo credit: Wiki Media Commons

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16 Responses to “How does morphine work?
8:33 pm November 20th, 2013


Could you tell me how long someone would need to be on Morphine to become somebody who is opioid tolerant rather then opioid naive ?


2:39 pm November 21st, 2013

Hello Viki. I’ve read that opiate dependence can develop after chronic, constant, daily dosing within a week, or two. While each person is unique, regular dosing will take users from opioid naive to opioid tolerant within a few weeks of round the clock dosing.

5:46 am April 30th, 2015

I was prescribed morphine for severe arthritis. However, it did not relieve any of my pain. But I had many of the side effects of morphine, such as brain fog, intermittent memory loss, poor judgment, sharp abdominal pain and constipation. I had no sedative effect and actually had sleep problems where I was unable to sleep at all for about three days in a row. Then I would sleep perhaps a few hours. Then unable again to get needed sleep. Therefore, I did not stay on morphine for a long period of time. Exalgo and hydromorphone actually worked to relieve my pain to a great degree, but not 100%, but peperhaps 60% or about that. But I did have some concerned side effects, so for me narcotics are not for me. I quit taking opiates totally and only take tramadol in addition to cortisone back infections which provides adequate pain relief and seemingly without any side effects.

2:23 pm May 4th, 2015

Hi Joanne. Morphine doesn’t always work 100% for everybody. I’m glad your current treatment is working for you.

9:06 pm August 26th, 2015

Joanne- Tramadol is an opiate. It may be the sulphate concentration or other factors causing your sleep issues.

5:01 pm October 20th, 2015

I am allergic to any meds that contain acetaminophen. I can’t tolerate tramadol. I pulled muscles in left thigh, buttocks, etc. I took 5mg.oxycodone w/food & had the dry heaves. It really did not help w/pain. Will morphine work o n me?

7:03 pm November 9th, 2015

Hi Mary. It should work well as it blocks even more severe pains. But, I still think you should first ask your doctor about any other acetaminophen-free pain killer solutions.

11:32 am March 9th, 2016

My husband had a stroke in Dec 2012. It affected his left side. In March of 2013 he started to have very bad pain on his left side, from shoulder down to his foot. He can’t sit and can only stand for a few minutes. He takes 1ml. of liquid morphine every 4 hours but this does relieve the pain. He’s been told it could be nerve pain. Doesn’t morphine help with nerve pain?

Lydia @ Addiction Blog
6:06 pm March 22nd, 2016

Hi Terri. Morphine is used to relieve severe pain that cannot be controlled by the use of other pain medications. You may find more information here:

12:28 pm March 30th, 2016

I have recently had an operation on my foot which I understand was quite involved. After the operation about forty mins I started vomiting it was horrendous bringing up nothing but air, I felt unbelievably ill, so I’ll in fact I refused any further medication but I did have water to sip after a very small sip of water I started vomiting again. Two and half hours or so a drip was put up(Hartman’s) I continued vomiting till four in the morning, by which time I had stopped sipping water and gave permission for an antiemetic to be given IV. My question is,Was it the amount of Morphine I was given which had slowed my intestine activity to near nil that caused such a horrendous long vomiting episode?

11:18 pm December 26th, 2016

Hi, I have been on prescription morphine to control lower back pain. I also feel that my mental facilities have become foggy. Also, my memory seems to be affected. Is there some way to continue my pain meds and clear up the foggy , and memory issues. I read everything I can get my I Pad to download. I play word games with my wife. All to try and rejuvenate my cerebral issues. Is there some other method to control pain other than mind fogging morphine? Help, I cannot fix myself. Thx. Tom C.

9:15 pm July 5th, 2017

I took a morphine 30mg extended release for the past couple of days. How long will it stay in my urine

Lydia @ Addiction Blog
5:23 pm July 10th, 2017

Hi Kathryn. Usually, morphine can be detected up to four days after the last use. But, this timeframe is longer for heavy/chronic users. If you want to learn more about drug testing, download our free e-book ‘The Definitive Guide To Drug Testing’:

7:50 pm September 9th, 2017

How can an 85 year old woman who lives alone be helped so she stops over using her morphine capsules?

Lydia @ Addiction Blog
1:38 pm September 14th, 2017

Hi Jose. Call the helpline you see on the website to get in touch with a trusted treatment consultant.

11:24 pm March 21st, 2018

How does Morphine enter the body what are the different ways?

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