Morphine Side Effects

Morphine is most commonly used as a means of providing pain relief. However, the side effects of morphine vary somewhat and while some of the adverse effects seen with initial therapy are short-term, others may be long-term, especially when the drug is used over longer durations of time.

Some common side effects associated with morphine use include:

  • Gastrointestinal side effects - These include nausea, vomiting, abdominal cramps and constipation. Opioid receptors for morphine are present in the gastrointestinal tract and their activation may lead to a slowing of gut movement, leading to constipation. Long-term use leads to severe constipation. In addition, morphine stimulates the vomiting centre of the brain causing nausea and vomiting. Morphine and codeine cause more nausea than other opioids. There may be drying of the mouth as well.
  • Sedation - Named after Morpheus, the Greek god of dreams, morphine is one of the most powerful sedative opioids. People taking morphine are therefore advised to refrain from driving and operating heavy machinery to avoid accidents.
  • Skin changes - Morphine may lead to the release of histamine in the skin leading to warmth, flushing and urticaria or allergic eruptions across the skin. Skin may appear cool and clammy and a severe chill called hypothermia may develop.
  • Shrunken pupils - Morphine may cause the pupils to constrict and appear pin-pointed in size.
  • Respiratory depression - The breathing mechanism can become suppressed in response to low blood oxygen. In healthy individuals, as blood oxygen falls and blood carbon dioxide rises, the drive for breathing increases. However, morphine suppresses this drive in the brain, potentially causing this very dangerous side effect. Respiratory depression is more common with higher doses.
  • Initial doses lead to euphoria but at higher doses unpleasant symptoms such as hallucinations, delirium, dizziness and confusion manifest. There may be some amount of headache and memory loss.
  • Biliary colic and subsequent severe abdominal pain is common in morphine overdose.
  • With high doses, muscle rigidity and abnormal movement of the limbs and muscles called myoclonus may manifest.
  • One of the prominent side effects of morphine use is the development of physical or psychological dependence on the drug and withdrawal symptoms when the drug is stopped. Morphine is a highly addictive substance and some of the withdrawal symptoms include pain, loss of sleep, nausea, vomiting, diarrhea, goose bumps, hot and cold flashes and intense craving.
  • Development of tolerance - Tolerance describes when a person needs to take a drug in higher doses to achieve the same degree of e.g. euphoria or pain relief as before. Developing a tolerance in this way often means addicts use higher doses of the drug.
  • Transmission of diseases such as HIV/AIDS and hepatitis B and C among drug abusers who use needles to inject the drug.

Reviewed by Sally Robertson, BSc

Further Reading

Last Updated: Sep 5, 2016



  1. Scott Reed Scott Reed United States says:

    "Transmission of diseases such as HIV/AIDS" , really stretching that one as a morphine side effect. This has got to be one of the poorest articles ever written.

    • Cynthia Beecher Cynthia Beecher United States says:

      SCOTT REED AND ALL WHO AGREE WITH HIM: Let me first state my credentials: RN, BSN Chemical Dependency Certified. Transmission of diseases such as HIV/AIDS is no where near stretching it. It's actually limiting it. Please don't forget HepC, Herpes, Chlamydia, Lice/Crabs, Syphilis, H Papilloma Virus, Genital Warts, Gonorrhea and the ones undiscovered. See, it goes like this: Drug and or alcohol use in itself lowers your physical resistance to disease and to fight off foreign invaders. The more chronic and multiple the use, the lower the resistance. On top of that, when under the influence of ANY of these drugs one's resistance to engage in sexual activity (not just in itself but the types of sexual activity as well - rough sex, anal sex, etc..) can be considerably lowered. Cap this all off with the fact that birds of a feather flock together - in other words people who are chronic drinkers, drugers and sexual cavorters tend to hang in the same social circles or areas. (The local bar for one example, or Jane Doe frequently has great parties house for another example.) Are you following me here so far Scott? So we have all these people of low resistance together. Let's throw in some IV drug users just for the heck of it because they are out there. Scramble it all up with people who are not in their right mind most of the time. People who's physical and mental defenses are low hanging in a group that has one of the HIGHEST INCIDENCES of HIV/AIDS in this day and age. (No Scott Reed it's no longer homosexuals - the have become fully educated and pretty much got it figured out). So, if after this explanation of how Morphine use can lead to misuse can lead to HIV/AIDS think again. Drug users (not just IV drug users by themselves but all drug users cumulatively) along with alcoholics (So say addicts in general) make up one of the largest growing populations of new HIV/AIDS patients that we have today. I know this because I got hired to teach the class on it by my hospital. (By the way this is all proven and factual - take any of the key words here and look them up and you will find studies, statistics, etc..).  So, if you think it's really stretching it, you might just think again. And it never hurts to get tested!

  2. Claudio Roberto Ortiz Claudio Roberto Ortiz Argentina says:

    la morfina o el lactulon te cambia el color de la materia fecal en mi caso voy de color amarillo claro

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