You need to be very careful, LD as vomiting can increase the risk factor of some poisons. I've also heard the egg remedy, as well as mustard & milk & large quantities of soda water (??) - to make them vomit (as I said, not always the best bet).

My advice is to go to the pharmacy now/tomorrow and buy some charcoal tablets & keep them in your first aid box. Should the unthinkable happen, force two or three charcoal tablets down them (they absorb the poison) and get them straight to the vet - as they'll need specialist treatment & possibly an IV.