Morphine

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Morphine is a major component of opium, a product of the poppy plant. Named after Morpheus, the Greek god of sleep, morphine is a powerful analgesic (painkiller). Doctors frequently prescribe it to relieve moderate to severe pain, especially in cancer patients. In the 1800s morphine was available in stores to anyone who wanted to buy it. At that time, little was known about physical dependence, and many people became addicted to morphine. Today, morphine is considered a controlled substance and is regulated by law. Because doctors know more about physical dependence, few patients become addicted to it.

Morphine produces a wide variety of actions, some desired and others not. The definition of a desired action and a side effect depends on the reason for using the drug. For example, opiates such as morphine can be used to treat diarrhea. However, a person taking morphine for pain would find constipation an undesirable side effect.

Constriction (narrowing) of the pupils of the eyes is one of the most widely recognized signs of opiate use. In addition, morphine produces sedation. At higher doses, morphine depresses respiration, meaning that the patient loses the ability to breathe automatically. Very high doses of morphine stop a person's breathing entirely—a common occurrence in overdoses. Another common side effect of morphine use is nausea.

Morphine is given either by mouth or by injection. Injection has much more potent or powerful effects. Physicians who are experts in the treatment of pain increasingly give morphine through continuous infusion. In order to avoid uneven treatment of pain (total relief when the drug is at its peak in the body; continued pain as the medication wears off), the morphine is diluted and given with fluid directly into the veins, at a very slow but steady rate. This keeps the concentration of morphine in the body at a steady state, so that the patient does not have periods of relief alternating with periods of pain. Another method of administering morphine involves a pump that allows the patient to push a button, releasing a tiny dose of morphine. The pump is set up to allow a specific dose of morphine at a specific time interval (sometimes as frequently as every five minutes). Some studies have shown that these patient- controlled analgesia (PCA) pumps are very effective at keeping a patient's pain to a minimum.

With chronic use, the effect of morphine lessens. In other words, a person develops tolerance to the drug's effects. To maintainthe effect the person received originally, it is necessary to increase the dose. When a person becomes physically dependent on morphine or other opiates, stopping the drug will bring on the withdrawal syndrome. Early symptoms of withdrawal include restlessness, tearing eyes, runny nose, yawning, and sweating. Eventually, further symptoms include dilated pupils, sneezing, elevations in heart rate and blood pressure, cramping, and gooseflesh. (The expression "cold turkey" comes from the look of the skin during withdrawal.)

Addiction: Concepts and Definitions; Opiate and Opioid Drug Abuse.