Respiratory depression: when mixing downers slows breathing
Alcohol, benzodiazepines, GHB, opioids and pregabalin each slow the brain's drive to breathe. Taken together the effects stack, so amounts that would be manageable alone can be enough together to slow breathing until it stops. It is the mechanism behind most overdose deaths involving more than one drug, and it often happens during sleep, hours after the last dose, when nobody is watching.
- They cannot be wokenNo response to their name, or to knuckles rubbed hard on the breastbone.
- Breathing is slow, shallow, or has stopped
- Snoring, gurgling or choking sounds while they are outThat sound is an airway struggling, not deep sleep.
- Lips or fingertips turning blue or grey
- Pinpoint pupilsA sign that opioids are involved.
- 01Call 911 and say they are not breathing properly.
- 02Give naloxone (Narcan) if there is any chance an opioid is involved.It has virtually no effect on someone who has not taken opioids, so there is no harm in giving it. It does not reverse alcohol, benzos or GHB, but street drugs often contain fentanyl nobody knew about.
- 03If they are not breathing, follow the dispatcher's instructions for rescue breaths.
- 04Once they are breathing, put them in the recovery position and stay.On their side, so vomit cannot block the airway. Naloxone can wear off before the opioid does.
If you are going to combine anyway
- Less of each, not the usual amount of both.Each one adds to the others. A normal dose of one plus a normal dose of another is a larger dose of the same effect.
- Do not redose while the first dose is still working.Pills, GHB and alcohol all take time to peak, and the peak is when breathing is lowest.
- Do not use alone, and do not let someone sleep it off unchecked.Someone who checks their breathing, and knows to roll them onto their side, is the whole difference.
- Carry naloxone.It is sold over the counter in US pharmacies, and often given away free.
How it happens
Breathing is not something you decide to do. A part of the brainstem sets the rate automatically, and it responds to rising carbon dioxide in the blood. Depressants blunt that response, so the body stops reacting to the signal that it needs more air.
Opioids act on that part of the brainstem directly. Alcohol, benzodiazepines and GHB act mostly through GABA, the brain's main slow-down signal. They get there by different routes, which is why combining them is worse than more of either one: nothing is left pushing the other way.
In 2016 the US FDA required its strongest warning, a boxed warning, on every opioid and benzodiazepine because of the deaths from taking the two together.
Substances that carry this risk
MixSafe raises a whole-mix warning when two or more of these are in the same mix. The list is kept narrow on purpose, so it is not every drug that can contribute. Each pair still has its own rating.