Opioids include a wide range of drugs such as codeine, morphine and heroin. Some are completely illegal, while others are legitimate prescription drugs open to abuse. One of the main factors preventing people from seeking treatment for opioid addiction is the terrible withdrawal symptoms caused when people stop taking the drugs: agitation, insomnia, diaorrhea, nausea and vomiting. Of the current drugs used for treating withdrawal symptoms clonidine can have severe side effects and methadone and buprenorphine can themselves be addictive. The drug ondansetron, which is already used to treat nausea and vomiting, blocks the receptors that are involved in maintaining opioid addiction and trials on mice have proved promising. A very small-scale study on humans also showed encouraging results.
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