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Morphine Side Effects

Serious Morphine Side Effects

Some side effects with morphine are potentially serious and should be reported immediately to your healthcare provider. These include, but are not limited to:
  • The urge to take more morphine than prescribed or for a non-medical purpose
  • Falling or unsteadiness
  • Unusual changes in mood or behavior
  • Severe constipation
  • Confusion
  • A slow heart rate (bradycardia)
  • Difficulty passing urine
  • Low blood pressure (hypotension)
  • Slow or irregular breathing
  • Severe drowsiness
  • Seizures
  • Signs of an allergic reaction, such as:


    • An unexplained rash
    • Hives
    • Itching
    • Swelling of the mouth or throat
    • Wheezing
    • Difficulty breathing.


It is common to develop non-allergic itching due to morphine. Morphine causes a release of histamine, resulting in itching unrelated to any allergy. If you develop itching but no other allergy symptoms, it is unlikely that you are allergic to morphine. However, make sure to let your healthcare provider know, as there are medications available to help relieve the itching.

Less Common Side Effects

There are other, less common morphine side effects that can occur. For these side effects, it is difficult to tell whether the side effect is caused by morphine or something else.
These less common morphine side effects include, but are not limited to:
  • A spinning sensation (vertigo)
  • Abnormal dreams
  • Absent menstrual periods
  • Accidental injury
  • Anemia
  • Back pain
  • Blurred vision or double vision
  • Changes in taste
  • Chills
  • Diarrhea and cramps
  • Difficulty passing urine
  • Difficulty swallowing
  • Dry mouth
  • Dry skin
  • Facial flushing
  • Fever
  • Fluid retention
  • Heart palpitations
  • Hiccups
  • High blood pressure (hypertension)
  • Indigestion or heartburn
  • Insomnia
  • Loss of appetite
  • Sexual side effects, such as impotence (erectile dysfunction, or ED), decreased sex drive, or abnormal ejaculation
  • Stiff or shaky muscles
  • Sweating
  • Taste changes
  • Thirst
  • Unusual dreams
  • Voice changes
  • Weakness
  • Weight loss.
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