What is a pill someone could overdose on?

Im trying to write a script based in a mental health part. What pills can somebody overdose on to attempt suicide?
Answers:
well, cyanide pills are very effective and i own heard of a lot of people doing that, and excluding that, narcotics are a drug of choice because they suppress your heart and breathing patterns. i hope this helped!
Traditionally, lethal pills are oval capsule, approximately the size of a pea, consisting of a thin-walled glass ampoule covered in brown rubber (to protect against accidental breakage) and jam-packed with a concentrated solution of potassium cyanide. It is important to note that purpose-made noxious pills (of the rubber-coated type) are never swallowed whole. Instead, they are first crushed between the user's molars to release the fast-acting poison contained within. Brain death occur within minutes and the heartbeat stops shortly after. A suicide pill swallowed without first being crushed would exceed harmlessly through the digestive tract.

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