Opioids act by attaching to and activating opioid receptor proteins, which are found on nerve cells in the brain, spinal cord, gastrointestinal tract, and other organs in the body. When these drugs attach to their receptors, they inhibit the transmission of pain signals. Opioids can also produce drowsiness, mental confusion, nausea, constipation, and respiratory depression, and since these drugs also act on brain regions involved in reward, they can induce euphoria, particularly when they are taken at a higher-than-prescribed dose or administered in other ways than intended. For example, OxyContin is an oral medication used to treat moderate to severe pain through a slow, steady release of the opioid. Some people who misuse OxyContin intensify their experience by snorting or injecting it. This is a very dangerous practice, greatly increasing the person’s risk for serious medical complications, including overdose.