As a narcotic, hydrocodone relieves pain by binding to opioid receptors in the brain and spinal cord. It can be taken with or without food as desired. When taken with alcohol, it can intensify drowsiness. It may interact with monoamine oxidase inhibitors, as well as other drugs that cause drowsiness. It is in FDA pregnancy category B: its effect on an embryo or fetus is not clearly known and pregnant women should consult their physicians before taking it. Common side effects include dizziness, lightheadedness, nausea, drowsiness, constipation, vomiting, and euphoria. Some less common side effects are allergic reaction, blood disorders, changes in mood, mental fogginess, anxiety, lethargy, difficulty urinating, spasm of the ureter, irregular or depressed respiration, and rash.