Fentanyl and morphine are similar, but not identical, as is shown by comparing the differences between the two opioids, including fentanyl to morphine conversion charts.

Fentanyl and morphine are two highly potent opioid pain-relievers. Both drugs effectively reduce pain but carry high abuse potentials. Morphine is most often used in hospitals and clinical settings to relieve post-surgical pain, while fentanyl may be prescribed to treat chronic pain including that of terminal cancer.

When comparing the two, many people question the similarities and differences between these two opioids. They may ask, “Is fentanyl stronger than morphine?” or “What’s the fentanyl to morphine conversion?” This guide can answer your questions, so you can compare fentanyl and morphine effectively.

What Is Fentanyl?

Known by its brand names ActiqDuragesicSublimaze, and Ionsys, fentanyl is a highly potent, synthetic opioid analgesic. Because of its potency, it is reserved for the most severe types of pain, including cancer pain. Fentanyl may also be prescribed to people with chronic pain who have an opioid tolerance. When used as directed, fentanyl can be administered via an injection, worn as a transdermal patch or taken as a lozenge.

Like other opioids, fentanyl attaches to the brain’s opioid receptors to block pain signals in the body. Given the potency of it, it is also highly addictive. If someone takes fentanyl without the approval of a doctor, or for non-medical purposes, the consequences can include addiction, overdose, and even death.

What Is Morphine?

Like fentanyl, morphine is an opioid pain reliever that is used in a clinical setting. It is available as a pillpatch or as an intravenous fluid. Morphine is one of the most well-known and widely used drugs in the pain medicine practice. Medical professionals often use morphine as the benchmark for comparing the strengths of other opioids. It is used in medical environments to treat a wide variety of pain, from moderate to chronic. Morphine may be administered for patients who experience a heart attack, a car accident, broken bones, kidney stones, cancer pain or a surgical procedure.

To relieve pain, morphine causes a flood of dopamine in the brain’s reward center. This can also cause a euphoric high, which makes it extremely addictive. People who use morphine for non-medical purposes, or beyond their prescription limits, can easily develop an addiction.

How are They Similar

When comparing fentanyl vs. morphine, it’s important to note that the two substances are similar in numerous ways.

Both substances are:
  • Opioids.
  • Prescription drugs.
  • Potent pain relievers that bind to the brain’s opioid receptors.
  • Available as transdermal patches, injections or in an oral form.
  • Used in a clinical setting.
  • Highly addictive.
  • Capable of causing physical and behavioral withdrawal symptoms.
  • Capable of causing an overdose.
  • Potentially obtained and used illegally.

Important Note About Opioids: Fentanyl and morphine are opioid drugs. They are not to be confused with anti-inflammatory drugs, nonsteroidal anti-inflammatory drugs (NSAIDS) or over-the-counter (OTC) pain relievers. Some forms of fentanyl and morphine may be long-acting substances, but are not designed to reduce fever or depress the nervous system.

How are They Different

One of the main differences between the two is that fentanyl is a synthetic opioid and morphine is a pure opiate derived from the opium poppy plant. As a class of drugs, opioids encompass both man-made opioid drugs and all opiate drugs that are derived from opium.

In terms of forms and applications, morphine is available in many more forms than fentanyl is. Morphine can be prescribed for a wider variety of pain, but may not be as useful for people with chronic pain. Fentanyl is not intended to be prescribed for acute pain. Instead, it’s used to treat different types of chronic pain, usually from cancer.

Beyond their uses and forms, one of the most important differences between the two is their potency. Fentanyl, in any form, is far more potent than any type of morphine. In fact, it is approximately 100 times stronger than morphine. This makes the use of fentanyl far less common, and more dangerous, than that of morphine.

How Much Stronger Is Fentanyl to Morphine?

While both are opioid drugs, but fentanyl is far stronger than morphine. For this reason, morphine is typically considered the safer of the two opioids, and it also has more applications than its stronger counterpart, fentanyl.

  • For perspective, the National Institute on Drug Abuse says that fentanyl is approximately 50 times more potent than heroin and 100 times stronger than morphine. Because of the strength of fentanyl, even a small amount can lead to an overdose or death. For example, just a quarter of a milligram of fentanyl can kill a person.
  • According to palliative treatment charts, the transdermal skin patch of fentanyl is approximately 80 times more potent than a similar form of morphine. This is based on performing a morphine to fentanyl conversion.

However, it’s important to note that the estimate above only considers legitimate prescriptions of fentanyl. Forms of fentanyl that are sold illicitly have the potential to be mixed with other substances and may be even stronger than prescription fentanyl.

To further understand the fentanyl to morphine conversion, you can use an online opioid dose calculator or speak with a physician, pharmacist or other medical professionals.

Overdose Potential Comparisons

Along with the high risk of dependence that fentanyl and morphine carry, both drugs also carry the potential for overdose. This can occur if someone takes increasingly large doses of either drug over time to achieve the same effects. Because most opioid drugs share the same physical and behavioral side effects, the symptoms of a fentanyl overdose can be very similar to those of a morphine overdose.

They share many of the same overdose symptoms, including:
  • Dizziness or clumsiness.
  • Confusion
  • Muscle weakness
  • Extreme lethargy
  • Hypoventilation (slow breathing)
  • Inability to speak
  • Slow heart rate
  • Itchiness
  • Nausea
  • Pinpoint pupils
  • Pale skin
  • Blue-colored lips and fingernails
  • Unconsciousness or coma
  • Death

An important similarity between a fentanyl overdose and a morphine overdose is that they can both be reversed with Narcan, the brand name of the drug naloxone. Available as a nasal spray and an injection, Narcan can reverse the symptoms of an opioid overdose to save someone’s life.

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Editor – Renee Deveney
As a contributor for Advanced Recovery Systems, Renee Deveney is passionate about helping people struggling with substance use disorder. With a family history of addiction, Renee is committed to opening up a proactive dialogue about substance use and mental health. Read more
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Medically Reviewed By – Dr. Obianuju Helen Okoye, MD, MBA, MS-Epi
Dr Helen Okoye is a highly accomplished and sought after American Public Health Physician with a medical degree (MD), an MBA in Healthcare Management, and a master's in Epidemiology/Public Health. Read more
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