What characterizes the "high" experienced from opioids?

The "high" experienced from opioids is primarily characterized by relaxation and euphoria. Opioids act on the nervous system by binding to specific receptors in the brain, which leads to feelings of intense pleasure and a significant reduction in pain. This feeling of euphoria can create a strong sense of well-being, often accompanied by deep relaxation. These effects are prompted by the release of neurotransmitters like dopamine, which contribute to feelings of happiness and reward.

The other options do not accurately capture the principal effects associated with opioid use. Increased alertness and heightened sense of reality are more typical of stimulant drugs, which lead to heightened arousal and energy. Enhanced mood may occur temporarily, but it does not encompass the profound sense of relaxation and euphoria that are hallmark effects of opioids. Therefore, the combination of relaxation and euphoria distinctly defines the high experienced with opioid usage.