'B is for Barbiturates' - A to Z of Pet Poisons

 

Phenobarbital

Quick facts:

• Poison(s): Drugs of the barbiturate class.  This group of drugs is used in human and veterinary medicine for anaesthesia, sedation, the relief of anxiety and insomnia, and prevention of seizures (fits).  Barbiturates form part of some 'lethal injection' cocktails used by the US penal system, and are also used in veterinary medicine for humane euthanasia of patients.  Barbiturates have abuse potential.
• Species affected:  All species, dogs are most likely to suffer accidental poisoning.
• Toxic dose:  Depends on the drug, route of administration, and the patient.  Any accidental barbiturate ingestion or overdose in an animal or a human is potentially serious.
• Symptoms:  Barbiturates are sedatives. Initial symptoms include weakness and sleepiness.  Low blood pressure and reduced breathing rate will develop, and depending on dose, may be followed by unconsciousness, coma, and death.
• Action:  Contact your veterinary surgeon as soon as possible if you believe your pet may have been exposed to any barbiturate.  In general accidental ingestion of any prescription, non-prescription, or 'recreational' drug may be extremely dangerous, and you should seek advice as soon as possible if you believe your pet may have been exposed to them.  It will be helpful to your veterinary surgeon and to poison control / advice services if you have the name of the drug, strength, and quantity to hand, as well as knowing the weight of your pet.
• Treatment:  Will depend on the drug, the dose to which the pet has been exposed, and the severity of symptoms at the time of presentation.  There is no specific antidote to barbiturate poisoning / overdose and treatment is focused on supporting the patient while the drug is cleared by their body.  Treatment may include gastric lavage (stomach pumping), giving supplemental oxygen or artificial respiration if breathing is severely compromised, intravenous fluids to support the circulation, and drugs to encourage the heart to beat more strongly.  Despite intensive management, if a sufficiently large dose of drug has been absorbed, barbiturate overdose is commonly fatal.

Barbiturates have become less commonly prescribed in human medicine over the past few decades because of the potential for abuse, and the very narrow margin between the dose required for a 'high' and that which will induce a fatal coma.  Safer drugs are now available for the treatment of anxiety and insomnia.  Barbiturates remain in quite common use in veterinary medicine.  Sodium thiopental is a general anaesthetic agent, though this is less used now than a couple of decades ago.  Pentobarbital is the drug commonly used in the UK for humane euthanasia of veterinary patients.  Phenobarbital (trade names include 'Epiphen') given in tablet form is used to prevent seizures (fits) in epileptic dogs.      

 

Accidental overdosing with medications prescribed for epileptic patients, or dogs deciding to 'scavenge' medications belonging to owners or members of their households are the common routes of exposure.  Rarer, but something which is seen occasionally, is barbiturate overdose in dogs or cats caused by them scavenging and eating remains of animals who had been 'put to sleep' with a barbiturate injection.  Please think carefully about where and how you bury pets' remains, particularly after euthanasia, and consider arranging for cremation if there is nowhere safe or appropriate in your garden to lay your pet to rest.

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