Common side effects include euphoria, constipation, nausea, vomiting, loss of appetite, drowsiness, dizziness, itching, dry mouth, and sweating. Severe side effects may include addiction, dependence, hallucinations, respiratory depression (a reduction in breathing), bradycardia, and low blood pressure. Those allergic to codeine may also be allergic to oxycodone. Use of oxycodone in early pregnancy appears relatively safe. Opioid withdrawal may occur if rapidly stopped. Oxycodone acts by activating the μ-opioid receptor. When taken by mouth, it has roughly 1.5 times the effect of the equivalent amount of morphine.