Morphine Side Effects

  • Generic Name or Active Ingridient: Morphine

General information

Morphine is the gold standard of pain medicine. It is the most abundant alkaloid in opium, found in unripe seedpods of the poppy plant. Scientists isolated morphine for the first time in 1804; this powerful painkiller was sold for the first time in 1827. Morphine mimics endorphins, the body's natural pain reliever.

Morphine is an opioid painkiller that works mostly on the mu receptors. Doctors prescribe morphine to reduce moderate to severe pain. Long-acting formulas are available to provide round-the-clock protection from chronic pain. These formulas contain enough morphine to relieve pain 12 to 24 hours.

Morphine is available in an immediate-release formula, as a concentrate, extended-release capsules or tablets, in an extended-release capsule along with naltrexone, soluble tablets, in a solution or suspension or as a suppository. Side effects vary slightly between formulas.

Morphine, like all medicine, may cause side effects. Most people experience no, or minor, side effects while using morphine. Nearly all side effects are not serious and disappear after continued use as prescribed. Some side effects are serious and require the attention of a medical professional.

The U.S. Drug Enforcement Agency, or DEA, classifies substances according to the potential for abuse. The DEA classifies morphine as a Schedule II narcotic, which means it carries a relatively high potential for abuse and mental or physical dependence as compared to other drugs.

Physical dependence means the individual will suffer withdrawal symptoms after the level of morphine drops in his system, because either he took a smaller dose of morphine than usual or he has taken a medication such as naloxone to reduce the amount of morphine in his system rapidly. Withdrawal symptoms include:

  • Abdominal Cramps
  • Agitation
  • Anxiety
  • Blurred Vision
  • Insomnia
  • Restlessness
  • Sweating
  • Tremor
  • Vomiting

Side effects associated with morphine are typical of any opioids. The most serious side effect is respiratory problems potentially leading to stopped breathing, circulatory depression, dangerously low blood pressure and shock. Physicians should expect side effects and treat patients accordingly.

Opioids such as morphine work directly on the breathing center in the brain; using morphine or other opioids may cause respiratory depression. Respiratory depression is a condition where the lungs do not adequately exchange oxygen and carbon dioxide. Symptoms of respiratory depression include changes in breathing rate, a bluish color around the eyes, lips or fingernails, sweating, unusual breathing patterns and grunting or wheezing. Respiratory depression is a life threatening medical emergency that requires immediate professional attention.

Non-serious and Serious Side Effects

Most commonly reported side effects are not serious and go away after continued use at prescribed doses. Continue using morphine if you experience non-serious side effects but report them to your physician if these adverse reactions become intolerable or do not go away on their own.

Non-serious side effects vary slightly between preparations. Side effects common to all morphine formulas include:

  • Constipation
  • Dizziness
  • Drowsiness
  • Headache
  • Lightheadedness
  • Nausea
  • Vomiting

Immediate-release, concentrate, extended-release capsules, suppositories, sustained-release tablets may cause a restless mood and sweating. Morphine suspension is associated with weakness in some individuals while Morphine/Naltrexone seems to cause a dry mouth, increased sweating, mild itching and tiredness. Some who take soluble morphine tablets experience an exaggerated sense of well-being or a restless mood.

Morphine solution is associated with a wide variety of additional non-serious side effects including changes in vision, dry mouth, frequent urination, poor coordination, lack of energy, loss of appetite,, pinpoint pupils, sleeplessness, sweating and weakness. Psychological side effects include agitation, anxiety, confusion, decreased sex drive, exaggerated sense of well-being, fear, mental clouding, mood swings or restless mood.

Some side effects are serious, requiring immediate medical attention. Stop taking this medication immediately and contact a doctor if you experience serious side effects. Most formulas of morphine are associated with serious side effects including:

  • Confusion
  • Fainting
  • Hallucinations
  • Mental or Mood Changes
  • Seizures
  • Slow, Shallow or Difficulty Breathing
  • Chest Pain or Pounding in the Chest

Immediate release, concentrate, extended release capsules, immediate release tablets, suppositories, sustained release tablets are associated with other side effects including disorientation, severe or persistent constipation or stomach pain, severe or persistent dizziness, drowsiness, or headache, swelling of the hands, ankles, or feet, trouble urinating, unusual bruising or bleeding, unusual tiredness or weakness, vision problems, especially blurred vision.

Other serious side effects associated with Morphine/Naltrexone Extended-Release Caplets include confusion, numbness of an arm or leg, severe dizziness or drowsiness, sudden, severe nausea, vomiting, or headache. Soluble Tablets may cause excessive drowsiness, shock, unusual or excessive sweating.

Serious side effects associated with morphine solution include decreased sexual ability, delirium, difficulty urinating, disorientation, flushing of the face, itching, menstrual changes, tremor and vomiting.

Morphine suspension may cause side effects such as delirium, difficulty urinating, disorientation, fever, flushing of the face, hallucinations, mood or mental changes, numbness or tingling, severe dizziness or lightheadedness, severe drowsiness, severe or persistent vomiting or constipation, tremor, trouble sleeping, unusual sweating and vision changes.

Sustained-Release formulas of morphine may cause additional side effects such as disorientation, severe or persistent constipation or stomach pain, severe or persistent dizziness, drowsiness, or headache. Other serious adverse reactions include swelling of the hands, ankles, or feet, trouble urinating, unusual bruising or bleeding, unusual tiredness or weakness, and vision changes, especially blurred vision.

An allergic reaction to morphine is a serious side effect. Stop taking morphine and seek medical help immediately if you think you are suffering an allergic reaction. Symptoms of an allergic reaction include rash, hives, itching, difficulty breathing, tightness in the chest and swelling of the mouth, face, lips, throat, or tongue.

By body system

Central Nervous System

Morphine acts on the central nervous system, or CNS. This opioid either excites the CNS or depresses it.

CNS side effects of morphine use include drowsiness, delirium, seizures, tremors, dizziness, muscle twitches, malaise, confusion and sedation. Some patients receiving continuous infusion of morphine and other opioids suffered inflammatory masses, some of which resulted in paralysis or other neurological problems.


Morphine may cause respiratory depression, a serious and life-threatening condition commonly associated with opioid use. During an episode of respiratory depression, the lungs do not adequately exchange oxygen and other blood gases. Symptoms of respiratory depression include slow or shallow breathing.

Patients with underlying heart and blood vessel disease may experience bronchospasms while taking morphine. Bronchospasms are a sudden tightening of some of the muscles in the lungs, causing a constriction of air passages, like in asthma.


Morphine use is associated with gastrointestinal side effects such as nausea, vomiting, upset stomach, constipation and dry mouth. Morphine causes increased heartburn and gastrointestinal reflux or intestinal obstruction in some people. Morphine can also worsen biliary colic, a condition affecting the ducts between the gall bladder and liver. This opioid may cause intense but uncoordinated contractions in the first part of the small intestine. It might also slow the rate at which the stomach empties its contents, resulting in food remaining in the stomach too long.


Any person who uses morphine for a long time may become physically dependent on this opioid. An opioid-dependent individual suffers uncomfortable withdrawal symptoms if he stops taking morphine suddenly or if he uses a medication that drastically reduces the level of morphine. Symptoms of opioid withdrawal include abdominal cramps, agitation, anxiety, blurred vision, convulsions, goose bumps, insomnia, restlessness, sweating, tremor and vomiting.


Morphine may cause low blood pressure in certain situations, especially in those suffering a heart attack.


Morphine is associated with psychiatric side effects such as agitation, fearfulness, hallucinations, paranoia, psychosis and thinking disturbances.


Some people who take morphine experience acute urinary retention. The risk for urinary retention increases when the patient receives morphine through an epidural or intrathecal injection into the spinal cord. This may cause urosepsis, a blood condition caused by a urinary tract infection, especially if the patient has had a procedure involving his urinary tract.


Morphine rarely causes a drop in platelets.


Morphine use is associated with menstrual irregularities including amenorrhea, which is the absence of a menstrual period. Morphine may decrease male potency and decreased libido in both men and women.


Chronic use of high morphine doses may result in involuntary muscle hyperactivity.


All formulations of morphine may cause sweating, flushing and pruritis, commonly known as itchiness. A doctor may prescribe 2.5 mg of droperidol to reduce pruritis associated with 2 mg or 4 mg doses of epidural morphine.


Morphine may affect your vision. Using this medication may cause keratoconjunctivitis, or inflammation of certain parts in the eye. Visual disturbances may occur. More than one-quarter of all IV morphine users experience a decrease in pupil size after receiving this opioid.


Patients experience hypersensitivity reactions rarely, including dangerous anaphylactic reactions, after using morphine.


Morphine consumers may feel a warm sensation.


Morphine may increase hepatic enzymes associated with liver disease.