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CrookedGrin78 t1_jefh5ir wrote

Reply to comment by ogbubbleberry in ELI5: If benzodiazepines are CNS depressants, why is it so hard to die from a overdose of them alone? by psychrolute

That's really interesting, thanks! This might answer a long-time question I've had, which is why some drugs are worse in combination than a higher dose of them would be on their own. I had always wondered how combining GHB and alcohol could be any worse than doing double the normal dose of either one on its own, but it sounds like maybe this is why?

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d0rf47 t1_jefphrh wrote

The reason is these types of drugs (GHB and ethanol) both interact with your brains GABA system which is the bodys inhibitory neurotransmitter. Your body uses it to essentially calm itself. This also has effects on heart rate and respiration. this is why they are dangerous. Since the both activate this system they essentially relax your body to the point where your heart can stop pumping(cardiac arrest) or your lungs stop functioning on their own (respiratory arrest)

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Other "depressant" drugs also have dangerous interactions since the systems they work on can also have similar effects on the same systems even though they work using different neurotransmitters, eg being heroin and alcohol. They activate different systems in the body, however these systems have similar effects such as decreased heart rate & lowered respiration. which is why they can also be a dangerous combination.

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This is also the reason these drugs are so physically addictive and cause dangerous withdrawl symptom. Since they work with such critical natural bodily responses, when you get dependent on them your body stops operating these systems normally and when the chemical substitute (let say alcohol in the example) is no longer present/available the system goes haywire since the body is no longer capable of regulating the system which is why ppl can suffer strokes or heart attacks if they attempt to detox without medical supervisions.

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CrookedGrin78 t1_jeftrgg wrote

Ah, but that sounds different from what other posters were saying, i.e., that combining certain CNS depressants is _worse_ than overdosing on either of them on their own, because they act on _different_ systems. So with GHB and alcohol, is that actually the case? Does one of them depress respiration and the other one does not? Or when people overdose on a combination of GHB and alcohol, is it just that they took a full dose of both and the combination was the same as it would have been if they had taken that big of an overdose of either one?

To put it another way, with certain combinations, it seems like the sum is greater than the whole of the parts (2+2=5), because Drug B is causing Drug A to create an effect that Drug A wouldn't create on its own, even if you overdosed on it.

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d0rf47 t1_jefzmsx wrote

its likely that the effects of one are potentiating the effects of the other. The bigger issue is a persons response to the drug and how their body metabolizes it. I am not a physician just some with a keen interest in pharmacology. CNS is your central nervous system, this system control much more than just breathing, certain drugs may affect the heart more while others affect the breathing more. the issue becomes troubling when the cns is suppressed enough that one of sub systems (breathing or heart) becomes so low that it either stop functioning and arrest begins or in some cases it may be that they are both still "functioning" but not properly and hypoxia can set in. My understanding with GHB and alcohol is that its the heart rate dropping which causes the dangerous effect.

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Nagi21 t1_jegs3ew wrote

You’re using the wrong math idea. It’s not 3+3=7, it’s 3*3=9

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CrookedGrin78 t1_jefu36k wrote

The kind of thing I'm describing is somewhat similar to combining an MAOI with a drug that's metabolized through a pathway that the MAOI suppresses: if you took either drug on its own, it wouldn't be a problem, but when you combine them, it's dangerous. I previously thought that a CNS depressant was a CNS depressant, but it sounds like that's not entirely true, since some CNS depressants inhibit respiration and some do not.

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