Opioids have pronounced behavioral effects in two domains – pain relief and intoxication (profound euphoria or “high”) – both of which are described below in detail. The intensity of the euphoric effect varies with the route of administration. Intravenous and smoked opioids produce a dramatic and intense pleasurable effect. Opioids can also impair cognitive function, block memory formation, and impair performance of cognitive and skilled tasks. Other behavioral effects of opioids are related to their non-central nervous system actions, many of which are considered side effects, such as pruritis (itching) and constipation.