Morphine is an opioid used to treat moderate to severe pain that can’t be managed by other medications or chronic pain. Common brands are MS Contin and Kadian.

Morphine has a boxed warning. Like all opioids, morphine has a risk of dependence (physical in the form of withdrawals and psychological which may manifest from withdrawal symptoms), generally with prolonged use.

Your doctor might prescribe morphine following an injury or a major surgery. They may also prescribe it to treat other types of severe pain, like cancer pain or pain following a heart attack.

Morphine goes by many brand names, including:

  • Kadian
  • MS Contin
  • Oramorph SR
  • Morphgesic
  • Arymo ER
  • Sevredol
  • Roxanol

Morphine is derived from the poppy plant. It works by blocking pain signals from reaching your brain.

Morphine is available in the following forms:

  • tablet
  • capsule
  • liquid
  • epidural
  • rectal suppository
  • nebulized (inhaled via a nebulizer)

It can be administered:

  • orally
  • intravenously (directly into a vein)
  • subcutaneously (beneath the skin)
  • intramuscular (directly into muscle)

Since morphine works in the pleasure centers of the brain, it has a high potential for misuse and addiction. For this reason, it’s classified as a federal controlled substance (Schedule II).

If you’re prescribed morphine for pain management, it’s important to understand how long the effects of the drug will last in your body.

It’s also important to talk to your doctor to learn how to decrease withdrawal symptoms if you decide to stop taking it.

The amount of morphine needed for pain relief varies widely from person to person. It’s influenced by factors such as:

  • previous opioid use
  • age (older adults may have a higher sensitivity to morphine)
  • general medical condition
  • dosage
  • method of administration

When taken by mouth, you’ll likely start feeling the effects of morphine within 30 to 60 minutes.

According to the product label, morphine reaches peak concentrations in the bloodstream in roughly 60 minutes after you take it orally.

If morphine is injected intravenously, you’ll likely begin feeling the effects quicker.

Extended-release formulations may take longer to reach peak concentration in the bloodstream.

Typically, your doctor will start you on a low dose and then increase the dose slowly until your pain is well managed.

People who’ve never taken an opioid before usually won’t need as much morphine in order to experience relief from their pain.

Over time, you may build up a tolerance to morphine. This means it may take longer to feel the pain relief, or the relief may not feel as strong.

When this happens, your doctor may want to increase your dose or switch you to a different type of pain medication. You shouldn’t take a larger dose of morphine without speaking to your doctor first.

You’ll likely stop “feeling” the pain relief of morphine in 4 to 6 hours. This is why your doctor may have you take a single tablet of morphine by mouth every 4 to 6 hours while you’re in pain.

If your doctor prescribes you an extended-release formulation, the effects will last for 8 to 12 hours. Some extended-release brands include:

  • MS Contin
  • Arymo ER
  • Kadian ER

Even though you’ll stop feeling the effects of morphine after a few hours, morphine will remain in your system for longer than that.

One way to find out how long a drug will last in the body is to measure its half-life. The half-life is the time it takes your body to eliminate half of the drug.

Morphine has an average half-life of 2 to 4 hours. In other words, it takes between 2 and 4 hours for your body to eliminate half of the dose of morphine.

The half-life fluctuates from person to person. This is because everyone metabolizes medications differently.

It takes several half-lives for a drug to be fully eliminated from the body. For most people, morphine will fully clear the blood in 12 hours.

However, morphine can still be detected in the saliva, urine, or hair for a longer period of time.

According to American Addiction Centers, morphine can be detected in:

  • urine for up to 3 days after the last dose is taken
  • saliva for up to 4 days after the last dose is taken
  • hair for up to 90 days after the last dose is taken

A number of factors can influence the time it takes for morphine to clear the body. These include:

  • age
  • weight
  • body fat content
  • metabolism
  • liver and kidney function
  • how long you’ve been taking morphine
  • if you’ve taken any type of opioid before
  • dosage
  • any medical condition you have
  • other medications you’re taking
  • alcohol
  • genetics

The effects of morphine are increased if you consume alcohol. Combining alcohol with morphine can also lead to dangerous side effects, including the possibility of a fatal overdose.

Taking cut, broken, chewed, crushed, or dissolved forms of morphine may lead to increased drug release into the body, which can increase your risk for overdose or even death.

Tell your doctor if you’re taking any of the following medications. These medications have been shown to interact with morphine and potentially increase its effects:

You shouldn’t stop taking morphine abruptly without consulting your doctor because of the possibility of having withdrawal symptoms.

Withdrawal symptoms occur when the body has become dependent on a drug. Dependence on morphine usually doesn’t occur until after several weeks of consistently taking the drug.

In drug dependence, the body has become used to the presence of a drug, so if you stop taking that drug suddenly, or if you miss a dose, you may experience predictable symptoms known as withdrawal.

Withdrawal symptoms include:

  • restlessness
  • irritability
  • yawning
  • lacrimation (abnormal or excessive secretion of tears)
  • sweating
  • anxiety
  • muscle spasms or twitching
  • back pain
  • diarrhea
  • widened pupils
  • inability to sleep (insomnia)
  • muscle cramps
  • vomiting
  • sweating
  • fast breathing
  • fast heart rate
  • high blood pressure

Your doctor may want you to reduce the dosage over time to prevent withdrawal. This is called tapering.

If you’ve been taking morphine for more than a couple of weeks, it’s recommended that the dose is decreased gradually while your doctor monitors you carefully for signs and symptoms of withdrawal.

The pain relief of a single dose of immediate-release morphine will likely wear off within 4 to 6 hours. However, the drug may still be detected in the following after taking the last dose:

  • saliva for up to 4 days
  • urine for up to 3 days
  • hair for up to 90 days

There are also a number of factors that could alter the time it takes for morphine to clear the body. These factors include:

  • age
  • metabolism
  • weight
  • dose
  • if you’re taking other drugs, including alcohol

Never take more than your prescribed dose of morphine, even if you feel that the medication isn’t working well. It’s possible to overdose on morphine. An overdose can be fatal.

Seek emergency medical care if you experience any of the following symptoms of a morphine overdose:

  • slow, shallow breathing
  • flaccid muscles
  • cold and clammy skin
  • constricted pupils
  • unresponsiveness
  • extreme sleepiness
  • slow heart rate (bradycardia)
  • nausea
  • vomiting
  • coma

Morphine is considered a powerful pain medication that’s highly addictive. Opioids such as morphine have led to many deaths due to overdose.

In 2017, approximately 47,000 people died from opioid prescription-related overdoses in the United States, according to the Centers for Disease Control and Prevention (CDC).

It’s important to only take your prescribed dose of morphine and to do it under your doctor’s supervision.

Before you decide to stop taking morphine, speak with your doctor. You will need to taper the dose in order to avoid having withdrawal symptoms.

Read the information in the medication guide before you begin treatment with morphine. Talk to your doctor if you have any questions or concerns.