Morphine is a powerful opioid drug derived from the opium poppy plant. Morphine is one of the most potent pain relievers available and is commonly used to treat post-surgical pain and pain caused by chronic medical conditions. Morphine is a Schedule II controlled substance under the Drug Enforcement Administration’s regulations, signifying the high potential for morphine addiction and abuse.
When morphine is used repeatedly over time, tolerance may develop. Tolerance means that it takes a higher dose of morphine to achieve the same level of pain relief initially produced. With repeated use of morphine, physical dependence also occurs. Dependence develops when the pain areas of the brain adapt to repeated exposure to the drug and only function properly when morphine is present.
When the morphine is removed, severe physical reactions can occur. These physical reactions are known as withdrawal syndrome. Dependence and addiction involve different areas of the brain, so it is possible to be dependent on morphine without being addicted to morphine. Dependence without addiction can easily occur in people treated with morphine for a chronic medical condition such as cancer.
So, why is morphine addictive? When morphine enters the body, it quickly travels to the brain. Once in the brain, morphine binds to opioid receptors and triggers the release of the neurotransmitter dopamine. Dopamine then produces euphoria and pleasurable feelings in the user. The opioid receptors are located in parts of the brain associated with reward and pain pathways.
The binding of morphine to areas in the pain pathway leads to loss of pain. However, the binding of morphine to regions of the brain involved in the reward pathway can contribute to the development of addiction. The reward pathway produces pleasurable feelings in response to natural factors such as food and drugs such as morphine.
Morphine binding to receptors in the reward pathways results in dopamine release and euphoria. This euphoria generates a positive reinforcement cycle that leads to repeated morphine use. Once this cycle becomes compulsive, morphine addiction can develop. Although morphine addiction is a serious condition that many people deal with, recovery can be achieved with the proper treatment.