Vicodin, Percocet, Oxycodone fall under the category of opioid narcotic analgesic drugs. Oxycodone, for example, is a semi-synthetic opioid synthesized from poppy-derived thebaine (also known as codeine methyl enol ether). Oxycodone has been in clinical use since 1916 and it is used for managing moderate to moderately severe acute or chronic pain and it was developed in 1917 in Germany as one of several new semi-synthetic opioids in an attempt to improve on the existing opioids. It has been found to improve quality of life for those with many types of pain. However, sometimes even taken as prescribed can cause dependence. Common side effects include euphoria, constipation, fatigue, dizziness, nausea, vomiting, dry mouth, anxiety, itching, and sweating. Less common side effects (experienced by less than 5% of patients) include loss of appetite, nervousness, abdominal pain, diarrhea, urine retention, dyspnea, and hiccups. In high doses, overdoses, or in patients not tolerant to opiates, oxycodone can cause shallow breathing, bradycardia, cold-clammy skin, apnea, hypotension, miosis, circulatory collapse, respiratory arrest, and death. The risk of experiencing severe withdrawal symptoms is high if a patient has become physically dependent or addicted and discontinues oxycodone abruptly. Therefore, particularly in cases where the drug has been taken regularly over an extended period, use should be discontinued gradually rather than abruptly. People who use oxycodone in a recreational, hazardous, or harmful fashion (not as intended by the prescribing physician) are at even higher risk of severe withdrawal symptoms, as they tend to use higher-than-prescribed doses. The symptoms of oxycodone withdrawal are the same as for other opiate-based painkillers, and may include “anxiety, panic attack, nausea, insomnia, muscle pain, muscle weakness, fevers, and other flu-like symptoms.”