Hi Jdogs,

There are two types of poisons. One type is an anticoagulant and causes your dog to start bleeding from different areas such as nose, rectum, penis, etc. Difethialone is an anticoagulant. The other type causes an increase in thirst, frequent urination, vomiting, weakness, muscle twitching, seizures and eventually death. Symptoms do not appear immediately but from 18 hours to several days later.

You will need to get your dog to vomit if it has been within 4 hours and then get your dog to the vet immediately.   Most likely the vet will start treatment with Vitamin K. If you can not get your dog to vomit, go immediately to the vet.

You can induce vomiting with hydrogen peroxide 3%. Instructions on dosage can be found here:
http://www.bichonfriseusa.com/ref/inducevom.htm

If you do not know of an emergency vet, you may be able to find one on this site.
http://www.pets911.com/services/emergency/index.php

More information can be found here
http://www.pugman.com/Pug%20Information/Rodent%20Poisoning.htm
http://www.vspn.org/Library/misc/VSPN_M01287.htm

And for difethialone here:
http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1012&context=vpcthirteen

I hope you find this information helpful.