Morphine Pharmacokinetics

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Morphine is a highly potent and addictive opioid that is used widely in clinical medicine and surgery for a variety of reasons. Due to the euphoria and pleasurable effects the drug exerts, it is also widely used for recreational purposes and is commonly abused by drug addicts.

Pharmacokinetics of morphine


Morphine is absorbed into the bloodstream via multiple routes of administration including:

  • Orally in the form of tablets or capsules.
  • Rectally inside suppositories or gel-coated capsules that can be inserted into the anus so the drug can be absorbed into the rectal blood vessels.
  • Intravenously using a hypodermic needle to inject the drug directly into the bloodstream. This is one of the fastest ways to feel the effects of the drug and is therefore one of the most common routes of administration.
  • By subcutaneous injection where the drug is injected into the subcutaneous tissue just underneath the top layer of the skin. This creates a depot from which morphine can be rapidly delivered into the bloodstream.
  • Morphine can also be injected into the spinal column for spinal or epidural anesthesia.
  • Morphine can also be inhaled or snorted in powder form.

Metabolism or breakdown

Once morphine reaches the bloodstream, it is carried to the liver where a large proportion of it is broken down, a process termed first-pass metabolism. Due to this first-pass metabolism, only around 40% to 50% of morphine reaches the central nervous system.

In the case of subcutaneous injection, blood levels of morphine peak after about 20 minutes and with oral ingestion, levels peak after about 30 minutes.

During metabolism, around 60% of morphine becomes morphine-3-glucuronide and 6% to 10% becomes morphine-6-glucuronide. The morphine is glucuronidated by the phase II metabolism enzyme UDP-glucuronosyl transferase-2B7. The drug may also be metabolized into small quantities of normorphine, codeine, and hydromorphone.


Around 90% of morphine taken is excreted from the body within 24 hours, mostly in the form of urine. Morphine has an elimination half-life of around 120 minutes. The drug can be stored in fat, so remains detectable for a long time after use and even after a person has died.

Further Reading

Last Updated: Jun 19, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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  1. Jeffrey Hearn Jeffrey Hearn Canada says:

    Here it says that morphine can be detected for a long time and other sites say that it only is detectable in urine for 2 to 3,days what's the real answer?

    • Tanver Doğanay Tanver Doğanay Turkey says:

      Dear Jeffrey Hearn,
      Here it is morphine can be detected for a long time and other sites say that it only is detectable in urine for 2 to 3,days what's the real answer?
      Morphine is detectable in urine for 2 to 3 days. Because, biological half life of morphine is about 2 hours and it is detectable in blood for 2, 3 days and it transfers to kidneys and after excretion, in urine it is detectable for 2, 3 days.
      On the other side,
      The drug can be transferred to fat tissue from blood stream and diffused throughout the fat tissue and stored there, without transfering to blood stream, so it remains detectable in fat tissue for a long time after use and even after a person has died.
      tanver doganay,  ta2ag

  2. JoAnne Bickel-Custer JoAnne Bickel-Custer United States says:

    Does daily small doses of morphine for pain, cause other organs to deteriorate quicker?

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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