What is a poison that can be given to a comatose patient that requires another character to get an antidote?

Basically, I need one main character to be comatose and the other one trying to save him. The antagonist has to give the main character a specific time period to jump through hoops or whatever to get the antidote.

I need something that either the killer injected before the accident that caused the coma (severe blood loss) or something he can administer afterwards.

And of course there needs to be an antidote as well.
Thanks for your help!

Edit: Adding some more information

The poison could definitely cause the coma. And for sure X has to wake up. As for the time frame I would say from the injection of poison it could happen right before the accident. The accident and the other stuff takes about an hour for him to reach the hospital. As for the antidote it's open atm it could be anywhere from 72 hours to seven days. The protagonist needs time to play the killer's game. And thanks for the response you guys!

posted about 7 years ago

Elle Harte‭

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