Hypoventilation is not synonymous with respiratory arrest, in which breathing ceases entirely and death occurs within minutes due to hypoxia and leads rapidly into complete anoxia, although both are medical emergencies.
Strong opiates (namely fentanyl, heroin, and morphine), barbiturates, and certain benzodiazepines (such as alprazolam) are known for depressing respiration.
In an overdose, an individual may cease breathing entirely (go into respiratory arrest) which is rapidly fatal without treatment.
Nevertheless, appropriate use of opioids in the right setting, as seen in patients with advanced cancer have been shown to be helpful, but must be monitored very carefully, nonetheless.
The opposite condition is hyperventilation (too much ventilation), resulting in low carbon dioxide levels (hypocapnia), rather than hypercapnia.