Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Treat any suspected prochlorperazine overdose as an emergency, even if there are no symptoms.
Contact your local poison control centre or emergency service immediately.
Stay with the person and follow the instructions you are given.
Call emergency services at once for:
Trouble breathing, blue or grey lips, or choking
Collapse, inability to wake, or a seizure
Severe neck, jaw, tongue, or throat spasms
Trouble swallowing or speaking caused by muscle tightening
A very fast, slow, or irregular heartbeat
High temperature with severe rigidity, confusion, or heavy sweating
Do not induce vomiting or give food, drinks, or home remedies unless a poison specialist or emergency professional tells you to do so.
Breathing or swallowing difficulty makes this an emergency.
And for anyone, someone who:
is unconscious, or cannot be woken
you believe has taken an overdose or swallowed something poisonous
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
2
Is any of this happening?
Be seen today
If you develop unusual eye, face, jaw, or neck movements after a normal prescribed dose, seek urgent medical advice.
Return for urgent assessment if marked sleepiness, spasms, fainting, breathing problems, fever, confusion, or a racing or irregular heartbeat develops.
3
Does any of this apply?
Book an appointment
After discharge, routine follow-up is appropriate for medication review and prevention planning.
And for anyone, someone who:
is having side effects from a medicine, or is struggling to take it as prescribed
The article also says
Do not drive if you are drowsy, confused, faint, or having muscle spasms.
Every sign above is quoted from the sofidex article on Prochlorperazine overdose. If you are not sure, err upward — it is always reasonable to be checked.