A narcotic is an addictive drug that reduces pain, induces sleep and may alter mood or behaviour. Aside from their clinical use in the treatment of pain, coughing and acute diarrhea, narcotics produce a general sense of well-being known as euphoria by reducing tension, anxiety, and aggression.

Narcotic use is associated with a variety of effects including drowsiness, itching, sleeplessness, inability to concentrate, apathy, lessened physical activity, constriction of the pupils, dilation of the subcutaneous blood vessels causing flushing of the face and neck, constipation, nausea, vomiting and, most significantly, respiratory depression.

Reference: science daily, https://www.sciencedaily.com/terms/narcotic.htm , consulted on july 5th,2019