Hello, thanks for your question today! I am Dr. Drew, and I am a licensed veterinarian. I'll be happy to help you in any way I can.
Promethazine overdose in dogs can cause low blood pressure, weakness, incoordination, staggering, and other similar signs.
It would be wise for you to bring your Pug to a veterinarian for examination, to include checking blood pressure,
there's no at-home remedy for ingestion of this medicine,
if it was ingested very recently (within the last 1-2 hours), then inducing vomiting may be of some value,
but if more time has passed, then that is not likely to help.