Amitriptyline (Elavil, Endep)
What is it used for?
Amitriptyline is a long-acting anti-anxiety medication that is usually given daily for a minimum period of several months. It is used in pets that have anxiety or behaviour problems that benefit from a long acting medication. Some examples include generalised anxiety, separation anxiety, aggression, or inappropriate urination.
How is it used?
Any behaviour medication works best when used alongside a behaviour modification.
Therapeutic effects are usually seen within 4-6 weeks. Medication is usually continued for at least two months after a good response to help support a behavioural modification plan. For most behaviour medications, 6-12 months is considered short term.
How does it work?
Human formulations of Amitriptyline (Elavil, Endep) are off-label use. This means they have not been through the regulatory trials for registration, however amitriptyline has been commonly used by veterinarians for many years and is regarded as a relatively safe medication with few long or short term side effects. This medication increases the amount of serotonin (a brain chemical that regulates anxiety and mood) over the long term. It also increases the level of noradrenaline, which can help to reduce arousal and anxiety. Amitriptyline belongs to a group of medicines called TCA (tricyclic antidepressants). More recently, this medication has been used to provide pain relief for nerve issues, and managed overactive bowels in humans.
What are the side effects?
The most common side effects when starting the medication include decreased appetite and lethargy. These are usually mild and only occur in the short term, resolving in 10-14 days. Generally pets will take ‘special’ meals (eg chicken) well and can be well managed over this period.
Other rare effects include vomiting, diarrhoea, constipation, panting, irritability, paradoxical increase in anxiety, noise sensitivity, increased drinking due to dry mouth and light sensitivity. Neurological signs such as trembling and shaking may be seen at higher doses.
If any of the above signs occur, please contact your veterinarian as soon as possible.
Are there any other interactions?
Some alternative therapies such as St John’s Wort and tryptophan supplements can cause more side effects. Other medications such as Trazodone (another behaviour medication), and Clonidine (catapres) may affect your pet. Speak to your vet about any other medications or supplements your pet is taking.
Where do I get it?
As a human medicine, Amitriptyline is available through a human pharmacy with a script.
Off label use
In Australia, we only have only one medication registered for treating behaviour problems. This means many of the medications we use are considered ‘off label’. These medications still have excellent evidence for their use, and lots of data about their effects and side effects, however it is essential that you feel well informed about their off label use. Please read all the information thoroughly to ensure you feel well informed about the risks and benefits of using this medication.