Morphine's effects on the body

Morphine affects the central nervous system by blocking pain receptors and spurring the release of endorphins. But the positive effects of pain relief can produce negative effects that can result in physical problems and addiction.


Morphine is a narcotic analgesic first isolated from opium in 1805 by German pharmacist Wilhelm Serturner. He named it morphine after Morpheus, the Greek god of dreams.

Pain Relief

Morphine relieves pain by flooding a group of receptors in the brain that take in endorphins and enkephalins, two molecules that work together in the body to dull pain and produce a sense of euphoria. Morphine helps the body produce those molecules in a much larger quantity than it can naturally supply to block pain receptors, creating a mild euphoria that further dulls the effects of pain.

Side Effects

The sedating effects of morphine have other positive results. It dulls the brain's cough reflex and has long been used as a cough suppressant. It also relieves fear and anxiety by producing a sense of euphoria with the release of endorphins. On the negative side, morphine's sedating effects impair physical and mental performance, decrease hunger and can produce severe constipation by slowing muscle movement in the bowels. The worst side effect is addiction as the body builds up a tolerance and becomes dependent on the drug. Addiction produces severe withdrawal symptoms when the body is deprived of morphine.

Addiction and Withdrawal Symptoms

The main problem with morphine is that the body quickly becomes dependent on it. When the body is suddenly deprived of morphine, it produces severe flu-like symptoms that include nausea, vomiting, diarrhoea, chills and a fierce craving for the rush of endorphins it had been producing but is no longer there. Long-term use also leads to tolerance as the body adjusts to the drug and requires more to relieve pain. Though rarely life-threatening, severe withdrawal symptoms can produce convulsions and seizures.

Positives and Negatives

While morphine is often used to treat serious injuries and conditions that produce consistent and severe pain, it is used sparingly because of the negative effects it can have on the body, most notably addiction. That's why lower-class opiates like codeine are often prescribed to relieve pain and morphine is typically reserved for serious and long-term pain.

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About the Author

Doug Desjardins is a journalist and research analyst. He has worked for more than a half-dozen newspapers, magazines and websites and hiswork has appeared in a number of publications including the Los Angeles Times and San Diego Magazine.