Morphine / naltrexone Side Effects

It is possible that some side effects of morphine / naltrexone may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

For the Consumer

Applies to morphine / naltrexone: oral capsule extended release

Along with its needed effects, morphine / naltrexone may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking morphine / naltrexone:

More common
  • Bloating or swelling of the face, arms, hands, lower legs, or feet
  • chills
  • confusion
  • constipation
  • drowsiness
  • feeling of warmth
  • irritability
  • mental depression
  • rapid weight gain
  • redness of the face, neck, arms, and occasionally, upper chest
  • relaxed and calm
  • restlessness
  • sleepiness
  • sudden sweating
  • tingling of the hands or feet
  • trembling or shaking of the hands or feet
  • unusual weight gain or loss
  • Abnormal dreams
  • being forgetful
  • blurred vision
  • burning while urinating
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • clumsiness or unsteadiness
  • confusion about identity, place, and time
  • darkened urine
  • decrease in frequency of urination
  • decrease in urine volume
  • decreased awareness or responsiveness
  • delusions
  • dementia
  • difficult or labored breathing
  • difficult or painful urination
  • difficulty in passing urine (dribbling)
  • dizziness, faintness, or lightheadedness when getting up from a lying or sitting position suddenly
  • fast heartbeat
  • feeling of warmth
  • fever
  • indigestion
  • loss of appetite
  • nausea
  • nervousness
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • redness of the face, neck, arms, and occasionally, upper chest
  • seeing, hearing, or feeling things that are not there
  • severe nausea or vomiting
  • severe sleepiness
  • sweating
  • tightness in the chest
  • unusual tiredness or weakness
  • vomiting
  • yellow eyes or skin

Some side effects of morphine / naltrexone may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common
  • Acid or sour stomach
  • anxiety
  • belching
  • decreased appetite
  • diarrhea
  • difficulty with moving
  • excess air or gas in the stomach or intestines
  • full feeling
  • heartburn
  • itching skin
  • muscle pain or stiffness
  • muscle spasm
  • pain in the joints
  • passing gas
  • sleepiness or unusual drowsiness
  • stomach discomfort or upset
  • unusual drowsiness, dullness, tiredness, weakness, or feeling of sluggishness
  • weight loss
  • Cold sweats
  • decreased interest in sexual intercourse
  • dizziness
  • dry mouth
  • general feeling of discomfort or illness
  • goosebumps
  • headache
  • inability to have or keep an erection
  • increased sweating
  • lack or loss of strength
  • loss in sexual ability, desire, drive, or performance
  • night sweats
  • pressure in the stomach
  • rash
  • stomach tenderness
  • swelling of the abdominal or stomach area
  • trouble sleeping
  • upper abdominal or stomach pain

For Healthcare Professionals

Applies to morphine / naltrexone: oral capsule extended release


Gastrointestinal side effects including constipation (up to 31.2%), nausea (up to 22.2%), vomiting (up to 8.4%), diarrhea (up to 7%), dry mouth (up to 5.7%), upper abdominal pain (up to 2.3%), dyspepsia, flatulence, stomach discomfort, abdominal distension, pancreatitis, abdominal discomfort, fecaloma, lower abdominal pain, and abdominal tenderness have been reported.

Nervous system

Nervous system side effects including somnolence (up to 13.9%), dizziness (up to 7.7%), headache (up to 6.9%), lethargy, sedation, tremor, depressed level of consciousness, mental impairment, memory impairment, disturbance in attention, stupor, paraesthesia, and abnormal coordination have been reported.


Dermatologic side effects including pruritus (up to 6.2%), hyperhidrosis (up to 3.4%), rash, piloerection, cold sweat, and night sweats have been reported.


General side effects including fatigue (up to 4.1%), chills, peripheral edema, irritability, malaise, asthenia, jittery feeling, and drug withdrawal syndrome have been reported.


Psychiatric side effects including insomnia (2.9%), anxiety (up to 2.2%), depression, restlessness, disorientation, abnormal thinking, mental status changes, confusional state, euphoric mood, hallucination, abnormal dreams, mood swings, and nervousness have been reported.


Cardiovascular side effects including flushing (up to 2.3%), hot flush, and hypotension have been reported.


Metabolic side effects including anorexia and decreased appetite have been reported.


Musculoskeletal side effects including arthralgia, muscle spasms, myalgia, and muscular weakness have been reported.


Ocular side effects including blurred vision have been reported.


Hepatic side effects including increased ALT and increased AST have been reported.


Renal side effects including urinary retention and dysuria have been reported.


Genitourinary side effects including erectile dysfunction have been reported.


Respiratory side effects including dyspnea and rhinorrhea have been reported.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.