Drug Information

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Brand Name
Common Name
morphine sustained release
How does this medication work? What will it do for me?

Morphine belongs to the class of medications called narcotic analgesics (pain relievers). These pain relievers are also known as opioid analgesics. This medication is used to treat severe chronic pain. It acts on the brain to increase pain tolerance.

Sustained-release pain relievers should only be used when chronic pain control is necessary and should not be used to treat acute, or short-term pain. Your doctor may prescribe additional pain relievers that act more quickly for treatment of acute or "breakthrough" pain.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

How should I use this medication?

The dose of long-acting morphine varies widely, based on need. Tablets or capsules should be taken every 12 or 24 hours on a regular schedule in order to achieve and maintain pain relief.

To ensure the medication works over a long period of time, the tablets or capsules must not be chewed or crushed, as this could result in too much morphine being released very quickly and could be fatal.  If you have difficulty swallowing tablets or capsules whole, contact your doctor. Some capsules may be opened and sprinkled on soft food. It may be taken with or without food.

Do not take this medication in higher doses or for a longer period of time than prescribed by your doctor.

Over time, this medication may produce tolerance and physical dependence as your body becomes used to the medication. Tolerance occurs when a dose that used to provide acceptable pain relief is no longer effective, and higher doses are required to achieve the same level of pain relief. Physical dependence is a state where the body will go into withdrawal if the medication is stopped suddenly. If you have been taking morphine on a regular basis for a long period of time, talk to your doctor before stopping the medication, as withdrawal effects can occur.

Tolerance and physical dependence are not the same as addiction. Addiction is defined as a psychological need to use the medication for reasons other than pain relief. Although people may become addicted to this medication, it is most common for people who have had addictions to other substances in the past.

You may experience withdrawal effects if you stop taking this medication suddenly after extended use. If you plan on stopping the medication, your doctor may want you to reduce the dose gradually to reduce the severity of withdrawal effects.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. Do not stop taking this medication without talking to your doctor first, and do not increase the dose of this medication without consulting your doctor. If you miss a dose, take it as soon as possible and continue on with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. If you miss several doses in a row, contact your doctor before restarting the medication. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protected from light and moisture. Keep out of reach of children.

What form(s) does this medication come in?

M.O.S.-SR is no longer being manufactured for sale in Canada. For brands that may still be available, search under morphine sustained release. This article is being kept available for reference purposes only. If you are using this medication, speak with your doctor or pharmacist for information about your treatment options.

Who should NOT take this medication?

Do not take this medication if you:

  • are allergic to morphine, other narcotic analgesics, or any ingredients of the medication
  • are experiencing acute alcoholism or delirium tremens
  • are experiencing psychosis caused by use of medications, drugs, or chemicals
  • are experiencing acute asthma or other obstructive airway disease
  • are experiencing acute respiratory depression
  • are pregnant or breast-feeding, in labour, or delivering
  • have abnormal heart rhythms
  • have a blockage of the gastrointestinal tract, particularly paralytic ileus
  • have a convulsive (seizure) disorder
  • have a head injury, a brain tumour, or increased pressure inside the head or spinal cord
  • have consumed alcohol or any medications containing alcohol
  • have cor pulmonale
  • have mild or intermittent short-term pain that can be treated with other medications
  • have severe depression of the central nervous system (i.e., sedation)
  • have a suspected abdominal condition that may require surgery
  • have taken an MAO inhibitor such as phenelzine or tranylcypromine in the past 14 days
What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • changes in vision
  • changes in sexual desire or activity
  • confusion
  • constipation
  • decrease or loss of appetite
  • dizziness, lightheadedness, or feeling faint
  • drowsiness
  • dry mouth
  • false sense of well-being
  • headache
  • itchiness
  • low blood pressure (dizziness or lightheadedness when rising from a reclining or sitting position)
  • nausea
  • sweating
  • trouble sleeping
  • unusual tiredness or weakness
  • vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • decreased coordination
  • fast, slow, or pounding heartbeat
  • hallucinations
  • signs of blocked bowel (e.g., abdominal pain, severe constipation, nausea)
  • skin rash
  • sleep apnea (e.g., temporary occurrences during sleep where you stop breathing)
  • symptoms of decreased adrenal gland function (e.g., nausea, vomiting, loss of appetite, weakness, fatigue, dizziness)
  • withdrawal symptoms (e.g., nausea, vomiting, diarrhea, anxiety, shivering, cold and clammy skin, body aches, loss of appetite, sweating)

Stop taking this medication and seek medical attention immediately if any of the following occur:

  • seizures
  • signs of overdose:
    • cold, clammy skin
    • confusion
    • convulsions (seizures)
    • dizziness (severe)
    • drowsiness (severe)
    • low blood pressure
    • nervousness or restlessness (severe)
    • pinpoint-sized pupils of eyes
    • slow heartbeat
    • slow or troubled breathing
    • weakness (severe)
  • signs of respiratory depression (e.g., slow, shallow, or weak breathing)
  • signs of serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
  • symptoms of serotonin syndrome (e.g., confusion, fast heartbeat, hallucinations, restlessness, shaking, shivering, sudden jerking of muscles, sweating)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Abdominal (stomach) conditions: Morphine and other narcotic medications may make the diagnosis of abdominal conditions more difficult or it may worsen these conditions. People who experience slower-than-normal passage of material through the digestive system may experience more side effects from morphine sustained release. If you have abdominal problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Accidental use: Accidental ingestion or use of as little as one dose of morphine by someone for whom it has not been prescribed can lead to a fatal overdose. Children are especially at risk. Keep this medication out of sight and reach of children.

Adrenal gland disorders: People who take opioid medications, such as morphine, for more than one month may experience symptoms of decreased adrenal gland function. The adrenal gland produces certain hormones that keep the body functioning normally. If you experience nausea or vomiting, decreased appetite, and feeling tired, weak, or dizzy, talk to your doctor.

Alcohol and other medications that cause drowsiness: Do not combine this medication with alcohol or other medications that cause drowsiness (e.g., antidepressants, sleeping pills, anxiety medications) since additional drowsiness or suppressed breathing can occur and be dangerous and possibly life-threatening.

Asthma and other respiratory conditions: Morphine may cause increased breathing difficulty for people having an acute asthma attack, or those with chronic obstructive pulmonary disease (chronic bronchitis, emphysema) or other conditions that affect breathing. If you have asthma or another breathing disorder, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Breathing: Morphine can suppress breathing, particularly if taken by someone who has not taken morphine before. This is a serious, potentially life-threatening condition. Morphine may cause sleep apnea to develop or worsen.

If you are at risk for breathing difficulties, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Keep this and all medications out of reach of children.

Dependence and withdrawal: Drug addiction is usually not a problem for people who require this medication for pain relief. Physical dependence (a need to take regular doses to prevent physical symptoms) has been associated with narcotic analgesics such as morphine. Withdrawal symptoms may be experienced if the dose is significantly reduced or suddenly discontinued. These symptoms include seizures, irritability, sleep problems, agitation, tremors, diarrhea, abdominal cramps, vomiting, headache, muscle cramps, extreme anxiety, tension, restlessness, sweating, and confusion. Reducing the dose gradually under medical supervision can help prevent or decrease these withdrawal symptoms when this medication is no longer required for pain control.

Dizziness: Morphine and other narcotics may cause dramatically reduced blood pressure, resulting in dizziness and unsteadiness. To reduce the possibility of severe dizziness, rise slowly when standing from a sitting or lying position.

Drowsiness/reduced alertness: Morphine may impair the mental or physical abilities needed for certain potentially hazardous activities such as driving a car or operating machinery. Avoid these activities until you know how this medication affects you.

Head injuries: Morphine can cause increased pressure inside the head. If you have an acute head injury or other conditions that increase your intracranial pressure (pressure inside the head), discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Increased pain perception: Rarely, people taking morphine sustained-release experience an unexplained increase in pain, or experience pain from things that shouldn’t normally cause pain. If you experience a different type of pain from the chronic pain being treated with this medication, talk to your doctor. You may require a different pain medication or a decreased dose.

Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Low blood pressure: Morphine can cause low blood pressure or make low blood pressure worse. If you experience severe dizziness, especially when standing from a lying or sitting position, contact your doctor.

Liver function: Decreased liver function or liver disease can cause this medication to build up in the body, causing side effects. If you have reduced liver function or liver disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Medical conditions: Morphine may cause increased symptoms or reduce the symptoms of worsening illness for people with Addison's disease, reduced thyroid function, enlarged prostate, stricture of the urethra, reduced pituitary function, anemia, severe malnutrition, active ulcerative colitis, and hypothyroidism (low thyroid). If you have any of these conditions, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Seizures: Morphine may worsen preexisting seizure disorders. If tolerance to the medication develops and the dosage is increased substantially above recommended levels, seizures may occur in people without a history of seizure disorders. If you have a seizure disorder, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Serotonin syndrome: Severe reactions are possible when morphine is combined with other medications that act on serotonin, such as tricyclic antidepressants and serotonin reuptake inhibitors (medications used to treat depression). Symptoms of a reaction may include muscle rigidity and spasms, difficulty moving, or changes in mental state including delirium and agitation. Coma and death are possible.

If you are taking antidepressants, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pancreatitis: Morphine can affect the muscles in your digestive tract and increase your risk of an inflamed pancreas (pancreatitis). Report signs of pancreatitis such as abdominal pain on the upper left side, back pain, nausea, fever, chills, rapid heartbeat, or swollen abdomen to your doctor immediately.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately. Infants born to people who have been taking morphine for long periods of time or who are physically dependent on morphine will also be physically dependent on the medication and may experience breathing difficulties as well as withdrawal symptoms.

Breast-feeding: This medication passes into breast milk. If you are breast-feeding and taking morphine sustained release, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: Accidental ingestion of this medication by children may lead to severe and even fatal consequences. Keep this medication out of the reach of children.

Seniors: Seniors may be more sensitive to the effects of morphine and may require lower doses.

What other drugs could interact with this medication?

There may be an interaction between morphine sustained release and any of the following:

  • abrocitinib
  • acetazolamide
  • aclidinium
  • alcohol
  • aldesleukin
  • aliskiren
  • alpha-agonists (e.g., clonidine, methyldopa)
  • alpha-blockers (e.g., alfuzosin, doxazosin, tamsulosin)
  • amiodarone
  • amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
  • angiotensin converting enzyme inhibitors (ACEIs; captopril, enalapril, ramipril)
  • angiotensin receptor blockers (ARBs; e.g., candesartan, irbesartan, losartan)
  • antihistamines (e.g., azelastine, cetirizine, doxylamine, diphenhydramine, hydroxyzine, loratadine, rupatadine)
  • anti-Parkinson's medications (e.g., apomorphine, bromocriptine, entacapone, levodopa, pramipexole, ropinirole, rotigotine)
  • antiplatelet medications (e.g., clopidogrel, pentoxifylline, prasugrel, ticagrelor)
  • antipsychotics (e.g., aripiprazole, cariprazine, chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
  • atropine
  • "azole" antifungals (e.g., itraconazole, ketoconazole)
  • barbiturates (e.g., butalbital, phenobarbital)
  • benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
  • beta-blockers (e.g., atenolol, carvedilol, labetalol, metoprolol, propranolol, sotalol)
  • benztropine
  • bortezomib
  • brimonidine
  • buprenorphine
  • butorphanol
  • calcium channel blockers (e.g., amlodipine, diltiazem, nifedipine, verapamil)
  • cannabis
  • CF transmembrane regulators (e.g., elexacaftor, ivacaftor, lumacaftor, tezacaftor)
  • chloral hydrate
  • clidinium
  • cobicistat
  • cyclosporine (systemic)
  • darifenacin
  • desmopressin
  • diazoxide
  • dimenhydrinate
  • diphenoxylate
  • disopyramide
  • diuretics (water pills; e.g., furosemide, hydrochlorothiazide, triamterene)
  • domperidone
  • dronedarone
  • efavirenz
  • elagolix
  • eliglustat
  • eluxadoline
  • enzalutamide
  • eplerenone
  • esketamine
  • fesoterodine
  • flibanserin
  • flunarizine
  • flaxseed oil
  • general anesthetics (medications used to put people to sleep before surgery)
  • glycopyrrolate
  • hepatitis C antiviral medications (e.g., glecaprevir, ledipasvir, velpatasvir)
  • hydralazine
  • ipratropium
  • iron sucrose
  • kava kava
  • ketotifen
  • lemborexant
  • linezolid
  • lithium
  • macrolide antibiotics (e.g., azithromycin, clarithromycin, erythromycin)
  • methadone
  • methazolamide
  • methylene blue
  • metoclopramide
  • mifepristone
  • mirtazapine
  • monoamine oxidase inhibitors (MAOIs; e.g., moclobemide, phenelzine, rasagiline, selegiline, tranylcypromine) taken within the past 14 days
  • muscle relaxants (e.g., baclofen, cyclobenzaprine, methocarbamol, orphenadrine)
  • nabilone
  • naltrexone
  • nirmatrelvir
  • nitrates (e.g., nitroglycerin, isosorbide dinitrate, isosorbide mononitrate)
  • obinutuzumab
  • olopatadine
  • other narcotic analgesics (e.g., codeine, fentanyl, meperidine, oxycodone, tapentadol, tramadol)
  • oxybutynin
  • pegvisomant
  • pentoxifylline
  • phosphodiesterase 5 inhibitors (e.g., sildenafil, tadalafil, vardenafil)
  • pizotifen
  • pomalidomide
  • prasugrel
  • pregabalin
  • propafenone
  • propiverine
  • protein kinase inhibitors (e.g., lapatinib, neratinib, tucatinib)
  • prucalopride
  • quinine
  • ranolazine
  • rifampin
  • riociguat
  • ritonavir
  • sacubitril
  • scopolamine
  • seizure medications (e.g., clobazam, gabapentin, levetiracetam, perampanel, primidone, rufinamide, topiramate, valproic acid)
  • selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, fluoxetine, paroxetine, sertraline, vortioxetine)
  • serotonin/norepinephrine reuptake inhibitors (SNRIs; e.g., desvenlafaxine, duloxetine, venlafaxine)
  • sodium oxybate
  • solifenacin
  • somatostatin analogues (e.g., lanreotide, octreotide, pasireotide)
  • spironolactone
  • tetrabenazine
  • thalidomide
  • ticagrelor
  • tizanidine
  • tolterodine
  • trazodone
  • tretinoin
  • trihexyphenidyl
  • trospium
  • tryptophan
  • tricyclic antidepressants (e.g., amitriptyline, clomipramine, desipramine, trimipramine)
  • umeclidinium
  • valerian
  • vilazodone
  • zolpidem
  • zopiclone

If you are taking any medications that have a sedating effect, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. In many cases, interactions are intended or are managed by close monitoring. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications that you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.

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