overdose
Meaning of overdose: The threshold is not a fixed quantity: body size, kidney and liver function, and whatever else is already on board all move it.
Definition of overdose
An overdose is exposure to more of a drug or other substance than the body can safely process, whether the substance was prescribed, bought without a prescription, or obtained illicitly. It may follow a dosing error, an interaction between drugs, a deliberate act, or a gradual buildup in someone whose kidneys or liver are clearing the substance more slowly than expected.
What decides how bad an overdose is?
Three things at once. The substance sets the ceiling, since some are tolerated in enormous excess while others have very little room between a working dose and a harmful one. The amount taken sets the position within that range. The person sets everything else: body size, age, kidney and liver function, whether the stomach was empty, tolerance built up through regular use, and what else is present. That last factor is easily underestimated. Two substances that are each survivable in excess can be dangerous together, and alcohol combined with a sedative medication is the everyday example. An over-the-counter product carries no assurance of a wide margin either, and several of the narrowest margins in common use sit on open shelves.
Which systems fail first?
| System affected | What it looks like |
|---|---|
| Breathing | Slow, shallow or stopped breathing, the usual mechanism of death in opioid excess |
| Heart rhythm | A racing, slowed or disorganized beat, and a fall in blood pressure |
| Brain | Drowsiness sliding into unconsciousness, or the opposite, agitation and seizures |
| Liver or kidney | Silent injury emerging over a day or more, with no early warning at all |
Why can someone look well at first?
Because the harm and the symptom do not have to arrive together. Some substances damage an organ quietly while the person feels nothing unusual, and the most familiar example is a common painkiller whose overdose produces little more than nausea before liver injury declares itself far later. Slow release formulations spread absorption over many hours, so the peak comes long after the tablets were swallowed. A few substances are harmless in themselves and become toxic only once the body has broken them down. Some overdoses have a specific antidote that blocks or reverses the effect; most do not, and are handled by supporting whichever system is failing until the substance clears. Every adverse effect of an overdose is judged against the substance involved rather than against the amount alone.
Used in a sentence
The patient was brought to the emergency department for evaluation of a suspected medication overdose.
Good to know
Not every overdose produces immediate symptoms, since some substances cause organ damage that becomes apparent only after a delay, and an early absence of symptoms does not indicate the exposure was minor.