If your animal has been poisoned, or you think it may have been poisoned, then:
-it needs treatment, and,
-you need advice.
 
CONTACT YOUR VETERINARY SURGEON.  
Contacting your veterinary surgeon now will be of more benefit to your pet, your animal, than reading the rest of this page.
In the United Kingdom veterinary surgeons are listed in the telephone Yellow Pages under the heading: "VETERINARY SURGEONS".
 
Any treatment or advice depends not only on the nature of the (suspected) poison but also on the nature of the patient and on the clinical state of the patient. Hence professional advice is essential and no agent-specific advice is given here.
 
The following points are though noted:

• Even during office hours it is generally better to telephone in advance.
  Advice can be given more quickly.
  If the veterinary surgeon is out (on visits, for example), the practice can make better arrangements so that you and your pet are seen more speedily.
   
• Minimise the patient's and other animals' exposure to the poison.
  Removing the patient from the poison is obvious.
  Make sure (your) other animals do not consume any.
  Try to ensure the patient and other animals do not (re-)eat vomit or faeces or groom each others' coats if these are contaminated.
   
• Help the vet identify the poison.
  If you can safely take the poison or a sample with you (preferably in the original container) do so.
  Your own medicines in their original packing will, for example, almost certainly be capable of being safely taken with you -if these are the cause of the problem.
  More toxic agents, unsealed sacks, leaking containers are not likely to be suitable to take with you. Not all plants are easy to transport -besides obvious examples such as nettles, the sap of some plants is highly irritant to the skin.  ASK ADVICE.