Which is a common symptom of an opioid overdose?

Respiratory depression is a hallmark symptom of opioid overdose and occurs due to the effects of opioids on the central nervous system that depresses the brain's respiratory centers. When an individual takes a dose of opioids that exceeds the body’s tolerance, the respiratory drive can diminish significantly, leading to inadequate breathing and potentially life-threatening situations. This effect raises the risk of hypoxia, where the brain and other organs do not receive sufficient oxygen.

In contrast, increased heart rate is usually seen in situations related to withdrawal or other stimulant medications rather than an overdose. Extreme agitation is associated more with withdrawal symptoms or anxiety rather than the depressive effects of opioids. Visual disturbances could occur with various substances but are not a primary concern linked to opioid overdose specifically. Thus, respiratory depression is the key indicator of a serious opioid overdose and warrants immediate medical attention.