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Boxed warning:

Morphine has US Food and Drug Administration (FDA) boxed warnings.¹ ²

Like other opioids, morphine carries a significant risk of addiction, abuse, and misuse, which may be fatal. Therefore, all patients taking morphine should be routinely monitored for signs of abuse. 

Morphine increases the risk of life-threatening respiratory depression, most commonly when starting the drug or following a dose increase. 

Prolonged use of morphine while pregnant may lead to neonatal opioid withdrawal syndrome, which can be fatal. People who are pregnant or planning to become pregnant should meet with their doctor to discuss taking steps to reduce the risk.

A person should not drink alcohol while taking morphine as it may lead to increased plasma levels and possibly morphine overdose.

The risk of severe side effects, including extreme sedation, respiratory depression, coma, and death, is highest among people taking benzodiazepines or other central nervous system depressants alongside morphine. These drugs should not be combined.

Finally, accidental ingestion of morphine may result in a fatal overdose. Therefore, the drug should be kept in a secure place out of the reach of children. 

What is morphine?

Morphine is an opioid prescribed for severe acute or chronic pain. It works on the opioid centers in the central nervous system to change how your body reacts to pain. Morphine blocks pain signals traveling along the nerves to the brain. As morphine is a strong painkiller, doctors only prescribe it when other painkillers fail to provide adequate pain relief. They may prescribe it after certain surgeries, after something like a car accident, or for cancer pain. Morphine is addictive, and some people abuse it.³

The extended-release formulas are prescribed only for severe pain that requires continuous and long-term management and where other options have proven inadequate. However, in some cases, doctors may prescribe morphine for people who have already taken opioid medications to treat pain and have developed tolerance to the drug or people who need something stronger to deliver pain relief.

It’s available in capsule, tablet, oral liquid, and injectable forms. Morphine is available by prescription only under its generic name and several brand names, including Morphabond, MD Contin, Avinza, Kadian, Roxanol-T, Arymo ER, and Oramorph SR.⁴

How do you take morphine?

Take morphine precisely as prescribed by your doctor. If something is unclear, ask your doctor for clarification. The dose and method of administering this medication vary depending on its form and formula. You can take morphine before or after meals.

Oral liquid morphine is a short-acting formula taken every four hours as needed. The other oral forms are extended-release tablets and extended-release capsules (lasting effect between 8 to 12 or 24 hours).

Measure the oral liquid using a marked measuring spoon, syringe, or medicine glass. Do not use household spoons as they aren’t precise. 

Swallow the extended-release capsules and tablets whole. Don’t chew or crush them or use broken extended-release pills. Chewing or crushing tablets can affect how your body processes morphine, increasing the risk of side effects and overdose.

If you cannot swallow an extended-release capsule, you may open it and sprinkle its contents onto some applesauce. Mix it well and eat it right away without chewing. Do not crush the beads to make them easier to mix in, as they’re precisely manufactured to deliver the right amount of medication gradually.

Morphine extended-release tablets or capsules work differently from the immediate release type. You cannot take the same amount.

If taking morphine suppositories, they are for rectal use only. Wash your hands before and after inserting them. To make the suppository easier to insert, place the pointed end under cold running water. Lie on your left and bring your right knee to your chest. Slowly insert the suppository into your rectum until it reaches an inch deep. Make sure it doesn't fall back out. Hold your buttocks together to keep the suppository inside. Lie down for another five minutes to help the suppositories stay in place and dissolve.

If you need the injectable form of morphine, a qualified healthcare professional will measure the dose and administer the medication.


Follow your doctor's instructions and the directions on the label. This article outlines typical doses. Continue taking morphine as prescribed by your doctor, even if your dose falls outside the usual range. Do not adjust your dose without guidance from your doctor.

The amount of medicine you’ll take depends on its strength and form. The number of doses you take per day, the time between doses, and the duration of treatment depend on the medical condition you’re taking morphine for, other health conditions you may have, and any history of drug misuse or abuse.

Doctors only prescribe higher strengths of prescription opioids (more than 100mg per day) in very specific and uncommon situations. They’ll consider a number of factors, including pain severity, chronicity, and tolerance. When doctors decide a high strength is appropriate, they’ll conduct close monitoring. Strengths greater than 100mg per day have been associated with an 8.9-fold increase in overdose risk, of which 12% are fatal. Further, doses greater than 120mg/day are associated with a 2.6-fold risk of clinical depression.⁵

The amount of morphine required for pain relief varies widely. Your doctor’s recommendation will depend on your:

  • General medical condition

  • Previous opioid use

  • Age

  • Method of administration

Seeing results

How long it’ll take to see results with morphine will depend on the form you take. If you take it orally, you’ll start feeling the effects within an hour. Typically, the immediate-release form provides pain relief sooner than the extended-release form. Injections are the fastest-acting type of morphine.

Doctors typically start with a low dose and then gradually increase the dosage, if needed, until the pain is well-controlled. People who haven’t taken opioids in the past usually require a very low dose to achieve the desired results.

You may build up a tolerance to morphine over time. That means it may take longer for the pain relief to become effective, or the drug may not control the pain for a certain period as expected. If this happens, your doctor might adjust your treatment plan. You should never take more than your usual dose or change your dosing schedule without speaking to your doctor.

Potential side effects of morphine

Opioids like morphine will cause different side effects depending on factors such as dosage and treatment duration.⁶ ⁷

When you first begin taking morphine, you may notice some side effects. If you experience new or unusual symptoms, discuss them with your doctor.

Common side effects of morphine include:

  • Sleepiness

  • Changes in heart rate

  • Constipation

  • Nausea and vomiting

  • Mood changes

  • Sweating

  • Weakness

  • Dizziness upon standing up

  • Difficulty urinating

These symptoms should improve within a few days. If they worsen or persist for more than a few days, consult your doctor as soon as possible.

Severe side effects requiring immediate medical attention

Serious side effects of morphine demand immediate medical attention. These may include:

Addiction, abuse, and misuse

Morphine carries a significant potential for addiction, abuse, and misuse. It’s not possible to predict who will be affected, but certain people face a higher risk of experiencing these severe side effects, including:

  • People with a personal or family history of substance or alcohol abuse 

  • Those with a family or personal history of mental illness

All patients should be closely monitored for signs of addiction, abuse, and misuse and should engage in intensive counseling if needed.

Signs of addiction, abuse, and misuse may include:

  • Isolating from social situations

  • Failing to fulfill obligations

  • Behavioral changes, including agitation or aggression

  • Unintended weight loss

  • Falling asleep in inappropriate settings or sleeping for longer than usual

  • Taking higher doses of morphine or taking it more often than prescribed

Life-threatening respiratory depression

Even when they’re used precisely as prescribed, opioids, including morphine, may lead to respiratory depression, which may be fatal. This severe side effect can occur at any time, but it’s most common at the start of treatment and following dosage increases. Respiratory depression demands immediate medical attention.

Signs of respiratory depression may include:

  • Slow and shallow breathing

  • Shortness of breath

  • Daytime sleepiness

  • Bluish-colored lips, fingers, or toes

  • Confusion

Adrenal insufficiency

Adrenal insufficiency linked to opioid use is most common following longer-term use (more than one month). 

Signs of adrenal insufficiency linked to opioid use may include:

  • Nausea and vomiting

  • Anorexia

  • Dizziness

  • Fatigue

  • Weakness

  • Low blood pressure

Severe hypotension

Morphine may trigger severely low blood pressure in some people. The risk is highest in people who are already at risk due to reduced blood volume or concurrent use of other drugs that also increase the risk.

Signs of severe hypotension include:

  • Dizziness or lightheadedness

  • Blurred vision

  • Weakness

  • Confusion

  • Fainting

  • Cold, clammy skin

Gastrointestinal problems

Morphine causes a reduction in motility and delayed digestion. It may also reduce pancreatic and biliary secretions, trigger spasms of the sphincters of Oddi (which regulate the release of substances that mix with food to facilitate digestion), and increase serum amylase (which aids in digestion).

Signs of gastrointestinal problems may include:

  • Constipation or incomplete emptying

  • Bloating

  • Abdominal pain

  • Gastroesophageal reflux


Morphine may increase the risk of developing seizures. Additionally, it may increase the frequency of episodes in people with existing seizure disorders.

Serotonin syndrome

Drugs affecting serotonin levels, including morphine, may trigger a rare, potentially fatal condition called serotonin syndrome. This condition is marked by an excess of serotonin within the body.

Symptoms of serotonin syndrome include:

  • Insomnia

  • Agitation

  • Confusion

  • Increased heart rate and blood pressure

  • Pupil dilation

  • Twitching, rigidity, or loss of control of the muscles

Other severe side effects associated with morphine include:

  • Apnea

  • Difficulty swallowing

  • Anemia

  • Amnesia

  • Delirium

  • Depression

  • Hallucinations

Long-term use of morphine

Morphine immediate-release is usually prescribed for acute (short-term) pain and not chronic pain, as dependence and overdose are serious concerns. According to the US Centers for Disease Control and Prevention (CDC), as many as one in four patients taking opioids long-term will develop an opioid use disorder.⁸

Extended-release forms are reserved for the management of severe pain that requires long-term around-the-clock treatment, with no other alternatives. However, chronic morphine usage can increase the risk of or worsen any of the above severe adverse effects. Additionally, it can disrupt the gut, hormones, and immune system.⁹

Common effects of long-term morphine use include:

  • Dry mouth

  • Poor appetite

  • Bloating

  • Reflux

  • Stomach pain

  • Chronic constipation

  • Weight loss

Hormonal changes associated with long-term morphine use may cause issues including:

  • Menstrual problems

  • Increased blood sugar levels

  • Sexual dysfunction

  • Immune system-related conditions, increasing the risk of infections

  • Osteoporosis and risk of fractures

Missed doses

People typically take morphine one, two, or three times daily. Since this medicine treats pain, forgetting doses is rare. However, if you fail to take a dose as scheduled, you could skip it and continue to your next scheduled dose as normal. However, if you’re in pain and can’t wait until your next scheduled dose, you’ll need to consult your doctor on how to proceed. They may advise you to take the missed dose as soon as you remember, as long as you reschedule your next dose to maintain your typical interval between the doses.

When you take your missed dose at an unusual time, adjusting your next scheduled dose is essential. For example, if you take morphine twice daily, take your next dose 12 hours after you take the dose you missed. Don’t resume your schedule by taking your next dose at its scheduled time.

Do not take two doses at once, close in time to each other, or exceed your prescribed dose within a 24-hour period to compensate for a missed dose, as this could increase your risk of overdose or death.


A morphine overdose can be fatal. The risk is significantly higher if the medication is not taken as prescribed or if it’s taken with alcohol or other central nervous system depressants.

Overdose symptoms may include:¹⁰

  • Severe dizziness

  • Pinpoint pupils

  • Slowed or no breathing

  • Cold and clammy skin

  • Slowed heart rate

  • Unresponsiveness or fainting

Seek immediate medical attention, call 911, or call Poison Control at 1-800-222-1222  immediately if you experience signs of an overdose or feel unwell after taking morphine.

You can ask your doctor for naloxone (a medication that reverses the opioid effects by blocking the brain centers in the brain that the morphine targets) to keep with you. Someone who cares for you should know how to administer naloxone and where you keep it. A pharmacist or doctor can show you and your caretaker how to use the medication safely to reverse an overdose. You’ll still need to seek emergency care after taking naloxone, but it’ll buy you the time you need to get the appropriate assessments and treatments.¹¹

What to discuss with your doctor before taking morphine

There are several topics you’ll need to discuss with your doctor before taking morphine, including:¹²

  • Any allergies to morphine, other medications, and general allergies. They will be able to tell you about any active or inactive ingredients that may affect you. 

  • Prescription or nonprescription medications, nutritional supplements, and herbs you're taking or planning to take. Your doctor might need to adjust the doses of your medications or watch you more closely for side effects.

  • Any previous history of prescription drug misuse or abuse and any other drug or alcohol addiction history.

  • Any mental health condition you currently have or previously struggled with, including suicidal thoughts or behaviors.

  • Current or planned pregnancies or breastfeeding.

  • Morphine can cause infertility in men and women, so you may wish to discuss this. 

  • Upcoming surgeries, including dental procedures.

  • Morphine may lead to constipation. Speak with your doctor if you're concerned about constipation.

Tell your doctor if you have any of these conditions:

Stopping morphine

You should never stop taking morphine abruptly without your doctor’s guidance. If you suddenly stop taking morphine, you may experience withdrawal effects, particularly if you have been taking it long-term. Withdrawal symptoms may include:

  • Restlessness

  • Runny nose

  • Sneezing

  • Muscle or joint pain

  • Widening of your pupils

  • Agitation

  • Anxiety

  • Weakness

  • Nausea

  • Appetite loss

If you decide to stop taking morphine, your doctor will lower your dosage gradually. However, if you experience severe side effects or an allergic reaction, stop taking morphine and seek medical help immediately.

Morphine during pregnancy and breastfeeding

Doctors sometimes use morphine to treat severe pain during pregnancy because there are limited options for pain relief in those situations. Morphine is not recommended for pregnant women if other options are available.

There is no adequate available data for the use of morphine in pregnant women to inform a drug-associated risk for severe congenital disorders and miscarriage. However, some studies have shown that exposure to opioids, like morphine, during pregnancy is linked to maternal death, preterm or stillbirth, neonatal abstinence syndrome, and congenital disorders. If someone is already taking morphine or must take it because their doctor has decided that the benefits outweigh the risks, they should only take it for short periods and under close medical monitoring.

Additionally, prolonged use of opioid analgesics during pregnancy for medical or nonmedical purposes can cause neonatal withdrawal syndrome shortly after birth. Symptoms include high-pitched crying, diarrhea, abnormal sleep patterns, vomiting, irritability, hyperactivity, tremors, and failure to gain weight. If you’ve taken opioids during your pregnancy, it is crucial to monitor your newborn for signs of neonatal opioid withdrawal syndrome and seek immediate medical advice if you observe any.

Morphine use while breastfeeding can cause infant drowsiness, central nervous system depression, and even death. Newborns are particularly sensitive to even the smallest doses. Monitor your infant closely for increased sleepiness, breathing difficulties, trouble breastfeeding, or limpness. Contact your medical provider immediately if you notice these issues.¹³

Interactions with other drugs and alcohol

Morphine interacts with various other drugs, including certain pain medications. For example, mixed opioid agonists/antagonists such as buprenorphine, nalbuphine, and pentazocine, or opioid antagonists such as naltrexone.¹⁴ Using any of these medications with morphine may decrease its effect, leading to withdrawal symptoms.

The risk of severe adverse effects (including slow and shallow breathing, severe dizziness, and sleepiness) may increase when you use this medication with other products with similar side effects. Speak with your doctor if you're taking any other substances, including opioids, alcohol, marijuana, drugs for cough, sleep, depression, anxiety, muscle relaxants, or antihistamines.

Taking morphine alongside benzodiazepines or other central nervous system depressants, including alcohol, increases the risk of severely low blood pressure, respiratory depression, extreme sedation, and coma. All of which may be fatal.

Using morphine with serotonergic drugs may result in serotonin syndrome, a condition characterized by too much serotonin in the body, which may be life-threatening.

Avoid the use of morphine if you are currently taking monoamine oxidase inhibitors (MAOIs) or have taken them within the past 14 days, as combining the two may lead to serotonin syndrome.

Ensure you check the labels on all your medications (including allergy or cough-and-cold products). They might contain ingredients that cause drowsiness. If you’re unsure about anything you read on a medication label, ask your doctor or pharmacist for clarification.

Allergy information

Speak with your doctor if you've had an unusual or allergic reaction to any medicines in the past. Also, let them know about any other allergies, such as foods, dyes, or preservatives. 

A severe allergic reaction to this drug is rare, but it can happen. If you experience any symptoms of a serious allergy, seek emergency medical attention. These symptoms include:

  • Rash

  • Severe dizziness

  • Itching and hives

  • Swelling of the face, lips, tongue, or throat

  • Hoarseness

  • Trouble breathing or swallowing

Research on effectiveness and safety

In their review of relevant research, a team of researchers found sufficient evidence to support the effectiveness of long-term treatment with opioids for pain management. They also concluded that risks associated with opioid use were more prevalent among people taking higher doses.¹⁵

Authors of an article published in the scientific journal Experimental and Clinical Psychopharmacology suggest that more research is needed to ascertain when and how doctors should prescribe opioids to provide adequate pain relief while limiting the risks of addiction and other adverse outcomes associated with opioid use.¹⁶

Tips and advice for taking morphine

The following tips can help you achieve optimal effectiveness while reducing the risk of side effects associated with morphine use.

  • Take morphine precisely as directed by your doctor. Don't change how you take your medication without speaking with your doctor first. If you take morphine differently than prescribed, you could experience side effects, dependence, overdose, or death.

  • Older adults are more vulnerable to side effects.

  • Don't suddenly stop using opioids. Withdrawal from opioids can cause symptoms such as muscle aches, restlessness, pupil dilation, yawning, sweatiness, chills, high blood pressure, diarrhea, and anxiousness. To prevent withdrawal symptoms, you may gradually decrease your dose over several days or weeks under your doctor’s supervision.

  • If you're taking immediate-release morphine, the medication works best if you take it as soon as you start to feel pain instead of waiting until it becomes unbearable.

  • Morphine can cause constipation. Drink lots of water, take fiber pills, or eat more fiber-rich foods (like apples, broccoli, and spinach). Speak with your doctor if your constipation doesn't improve or worsens with time.

  • Don't drink alcohol or take any medications that make you tired.

  • Morphine can make you tired. Don't drive a car or operate any machinery until you know how it affects you.

  • Morphine may make you feel dizzy, lightheaded, and faint if you get up too quickly after lying down. To prevent this, get out of bed slowly and rest your feet on the floor for a few minutes before rising.

  • Keep morphine out of reach. If you no longer need morphine, dispose of the medication through a take-back program or flush it down the toilet. It reduces the risk of an accidental overdose, especially if you have children at home, and prevents medication misuse.¹⁷

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Here at HealthMatch, we’ve done our best to ensure that the information provided in this article is helpful, up to date, and, most importantly, accurate.

However, we can’t replace the one-to-one advice of a qualified medical practitioner or outline all of the possible risks associated with this particular drug and your circumstances.

It is therefore important for you to note that the information contained in this article does not constitute professional medical or healthcare advice, diagnosis or recommendation of treatment and is not intended to, nor should be used to, replace professional medical advice. This article may not always be up to date and is not exhaustive of all of the risks and considerations relevant to this particular drug. In no circumstances should this article be relied upon without independent consideration and confirmation by a qualified medical practitioner.

Your doctor will be able to explain all possible uses, dosages, precautions, interactions with other drugs, and other potential adverse effects, and you should always talk to them about any kind of medication you are taking, thinking about taking or wanting to stop taking.

Curious about clinical trials?

Access the latest treatments and medications. unavailable elsewhere - entirely free of charge. We make it easy to take part.