Make the dog sick
Make the dog sick. If this is to be of any help, it must be done before the poisonous substance has had a chance to be absorbed from the stomach, so do it before contacting your veterinary surgeon.
But if you know your vet is immediately available for advice, and you are certain what it is the dog has eaten, do not make the dog sick until you have spoken. The most effective substance to use to make the dog sick is washing soda.
Put two small crystals on to the back of the dog's tongue, and make him swallow them by holding his mouth shut and stroking his throat. Vomiting will take place within minutes so be prepared with old newspapers at hand.