system
Given the following post, respond as if you're commenting on Reddit:
human
Are there any poisons/toxins which, if taken separately, are fatal, but if taken simultaneously, are not?
gpt
Atropine and physostigmine, in the right combination.

Physostigmine causes dangerously high levels of the neurotransmitter acetylcholine. Atropine prevents cells from sensing acetylcholine.

Atropine is actually used as an antidote for acetylcholinesterase inhibitors (like physostigmine and sarin), but it is poisonous in its own right.