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How long does morphine last?

Therapeutic effects of morphine generally last for about 4 hours, although duration of action is related to mode of administration as well as details about individual dosing. More here on how long morphine lasts. Then, we invite your questions about morphine, including signs of morphine addiction and getting treatment for morphine addiction, at the end.

Morphine effects on the body and brain

Morphine induces a wide range of pharmacologic effects on the body and brain such as analgesia, euphoria, somnolence, respiratory depression, diminished gastrointestinal motility and physical dependence. However, morphine also has the potential to change the way the brain functions. Why is this?

This is because morphine acts on the central nervous system in different ways, affecting the m-receptors, the k- and d-receptors respectively. Additionally, analgesia induced by morphine is activating at least three areas of the central nervous system: the periaqueductal-periventricular gray matter, the ventromedial medulla and the spinal cord.

Morphine, when administered according to a schedule, may affect from one to all three areas at once, which will manifest a greater number of effects. In terms of specific effect on the body, the m-receptors are responsible for the modulation of pain, analgesic effects, respiratory depression, miosis, feeling of euphoria, and decreased gastrointestinal activity. The group of m 2-receptors is involved in drowsiness, nausea, and mental clouding while the k-receptors are involved in analgesia, diuresis, sedation, dysphoria. The d-receptors are also affected by morphine and are involved in delusions and hallucinations.

Morphine duration of action

The terminal half-life for morphine varies between 1.5 and 4.5 hours. However, patients have reported much longer duration of action due to higher dose administration or protracted use. Keep in mind that (for all modes of administration) late respiratory depression can occur up to 24 hours after administration of morphine.

Epidurally injected as part of anesthesia, morphine acts really strong and fast, due to the circulation of morphine in spinal fluids, which get directly to the brain. In such cases peak plasma concentrations are reached within 15 minutes after administration of 3mg of morphine.

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How long do morphine effects last?

Duration of action of the effects of morphine depend upon the mode of administration. When morphine is administered through epidural injection into the spinal fluid, it has a terminal half-life varying from 39 to 249 minutes. That is a bit shorter range compared to intravenous or intramuscular injection of 1.5 to 4.5 hours. And believe it, or not, only 4% of the morphine dose reaches to the brain. After intrathecal bolus injection of morphine, there is a rapid distribution phase of 15 to 30 minutes and a half-life in the of 42-136 min.

How long does a morphine high last?

Euphoric effects of morphine last for 4 to 6 hours. Onset of morphine effects takes place in 15 to 60 minutes. One interesting fact about morphine use is that as you grow older, the analgesia will last longer even with the same dose of morphine administered and you will experience the same high effects.

Morphine time in the body

A regular morphine user begins to eliminate morphine within 2 hours of administration of a single dose. Only 36% of morphine binds with proteins and 54% for muscle tissue. Excreted by the kidneys through urine in about 90%, only 10% are left to feces to eliminate morphine out of the body. However, up to 12% of morphine manages to leave the body without being metabolized and remains unchanged and can be recovered in the urine. In terms of drug testing, morphine can be detected in urine based drug tests up to a day or two after dosing.

Morphine high effects

As with any other drug, euphoric effects depend on the dose of morphine is administered, the route is taken, the history of drug abuse and dependence, the level of tolerance developed to morphine etc. Here is a list of the most common effects that can occur even as you feel effects of euphoria.

  • analgesia
  • constipation
  • cramping
  • depressed consciousness
  • depressed heart rate
  • diminished reflexes
  • drowsiness
  • euphoria
  • flushing of face and neck
  • lethargy
  • mental clouding
  • nausea and vomiting
  • pupils fixed and constricted
  • reduced gastrointestinal activity
  • relaxation
  • respiratory depression
  • sedation
  • sweating

Morphine duration questions

Do you still have questions about the duration of action of morphine, its excretion, or effects? We invite you to use the following section for your comments and questions. We try to respond with a personal and prompt answer ASAP.

Reference Sources: Hazardous Susbstances Data Bank TOXNET: Morphine
National Highway and traffic Safety Administration: Morphine (And Heroin)
Daily Med: Astramorph (morphine sulfate) Injection [AstraZeneca LP]

Photo credit: Public Domain Pictures

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15 Responses to “How long does morphine last?
8:49 pm December 13th, 2014

Husband was injected with morphine at er. How long after injection can he start taking Tylenol codeine?

2:27 pm December 29th, 2014

Hi Jennifer. You can get the best and most accurate advise from your doctor. So, please call him/her as soon as possible and remember that every person metabolizes and eliminates substances at a different rate.

7:33 am March 13th, 2015

I was given morphine 3-4 times within a 4 hour period of being in a serious roll over accident. However, when I had a blood sample taken from me approximately 2-2.5 hours after administration intravenously, there was no trace of the morphine in my blood sample. What could the possibilities be for this conclusion? I know that for a fact the test was for any known chemical substance including alcohol. Please give me some insight on this matter.
Thank you

1:39 pm November 1st, 2015

I’ve been on morphine and oxy cotton for 8 years the Dr now have taken me off of them. how long will it take for both of the drugs to get out of my system and for me to lead a normal life again

7:07 pm November 10th, 2015

Hello Jackie. Since you’ve been taking morphine and oxy cotton for a long time, so it could take mounts for the drugs to leave your system. However, with a good tapering plan prescribed by your doctor, you will be able to withdrawal safely.

Little bear
10:36 am December 15th, 2015

I take 15 mg ir morphine every 6 hrs i take morphine 15 mg er every 12 is it OK to take narco in stead of 15 mg ir

Lydia @ Addiction Blog
1:02 pm December 15th, 2015

Hi, Little Bear. I suggest you consult your doctor for any changes in taking your medicine, or call your pharmacist for advice.

12:19 am January 18th, 2016

Hi, I recently had cancer surgery and was given a morphine epidural for pain management. I so disliked the hallucinogenic effects that I insisted the medication be stopped after 3 days. After that I was on no drugs whatsoever. However the euphoria lasted for over three weeks. Is this unusual? Thank you.

4:02 pm January 23rd, 2016

I take 2.5 mills a day is this a lot

6:22 am June 20th, 2016

Is 100 mg er of morphine ear very strong? I have chronic back conditions with constant pain. I went from 60 to 100 but really could not tell much difference.

11:27 pm July 4th, 2016


My friend just received a shot of morphine after dislocating his shoulder. However, we are on vacation and we are wondering if it is safe for him to drink alcohol about 4 hours after taking the shot.

7:30 am July 8th, 2016

I have been taking 200 MG of morphine once and rarely twice a day for nearly 3 months. I’ve been wanting to quit and now that I’m going for a new job that does random drug test I need to quit. How long will it take for me not to test negative for the job and how long will it be going thru with drawls?

10:04 pm September 13th, 2016

if given at hospital on 9/12/2016 3:15pm will it show up on pre-employment drug screen scheduled for 9/15/2016

Lydia @ Addiction Blog
12:25 pm September 14th, 2016

Hi Patrick. It might show up on the drug test. But, tell the toxicologist that you were given morphine at the hospital, and show the medical report.

10:47 pm March 17th, 2017

I have left over Morphine Pills, how long before I throw them away?

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