ELI5: What is exactly happening in a person body whey they overdose?
Posted Apr 8, 2018, 11:00 PM UTC
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That depends greatly on WHAT they have overdosed on.
Opioid overdose causes respiratory depression, sometimes to the point where they stop breathing. Not breathing will lead to hypoxia, brain damage, and death.
Other drugs or substances cause a very wide range of other symptoms, depends on the substance. You can over overdose on water, in which case the damage is caused by hyponatremia (loss of electrolytes) leading to cardiac arrythmia
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It depends on the drug. Every substance (from water to cyanide) has what they call an "LD50" that is the dosage (in mg per kilo of mass of the subject) that will result in the deaths of 50% of the subjects.
LD50 = Lethal Dose 50%
So without asking about a specific substance, we can't really tell you what's happening.
Yeah probably should have been less vague, I’m thinking specifically on drugs like heroin and cocaine.
Heroin, an opioid, will suppress your respiratory drive. Deep in your brain, there’s an area which is always running (even when you’re asleep) that senses the oxygen and carbon dioxide in your blood and tells your lungs to breath. Opioids suppress neural firing in this area, leading to a decrease in the “breathe!” Signal coming from the brain. With enough opioids eventually this signal goes away entirely, you stop breathing and you die.
As for cocaine it’s a bit more complicated - you can die from multiple different effects it has on your body. But the quintessential cocaine OD is due to heart attack. Cocaine increases the amount of a group of molecules called catecholamines available in your body. These molecules (called dopamine, norepinephrine, and epinephrine) have a whole host of effects. The main pleasurable/addictive effect of cocaine is due to dopamine. However the epinephrine and norepinephrine cause an increase in your heart rate, and increase in how “hard” your heart beats (called contractility). At the same time they make your arteries constrict, making it much harder for the heart to pump blood to your body. These two effects mean the heart is using up WAY more oxygen than it usually would. But the kicker is these catecholamines have particularly strong activity on the arteries that bring blood and oxygen to the heart ITSELF. So you’re decreasing the blood flow to the heart while increasing the blood demand.
The result, if the dose is high enough, is that eventually the muscle of the heart runs out of oxygen and dies. And without a heart to pump blood to your body, you die along with it.