Respiratory depression can be described as a reduced urge to breathe that can be fatal depending on its intensity. At relatively safe levels, this effect typically causes a "sighing" pattern of breathing which can be described as deep breaths separated by abnormally long pauses. At higher levels, however, an individual may cease breathing entirely in a manner which is rapidly fatal without immediate treatment.
This effect is capable of manifesting itself across the 4 different levels of intensity described below:
Minimal respiratory depression
Moderate respiratory depression
Severe respiratory depression
Respiratory depression is often accompanied by other coinciding effects such as sedation and sleepiness. It is most commonly induced under the influence of heavy dosages of depressant compounds, particularly opioids, such as heroin and fentanyl, or GABAergics, such as alcohol and GHB. However, it is worth noting that otherwise safe dosages of these compounds can become fatal when combined with even small amounts of other classes of depressant. For example, benzodiazepines combined with opioids are an extremely common cause of fatal respiratory depression. It is therefore strongly discouraged to combine these depressants at any dosage range.
To prevent death, it is recommended to contact emergency medical services immediately in case of severe respiratory depression. If caused by an opioid overdose, an opioid antagonist, such as naloxone, should be administered. Many harm reduction organizations provide naloxone to users for free or it can be bought at pharmacies (including Walgreens and CVS in the U.S.). Naloxone will rapidly reverse the respiratory depression unless complicated by other depressants.
For other drug-induced respiratory depression, hospitalization and the assistance of a mechanical breathing machine may be necessary.