(for veterinary information only)


10 mg, 25 mg, 50 mg,     
75 mg, 100 mg AND 150 mg


Amitriptyline was developed out of a need in human medicine for anti-anxiety medications in the treatment of mental illness though, in humans, it has gained some popularity for the treatment of chronic pain syndromes, especially interstitial cystitis.

This medication creates its effects via several mechanisms:

  • By blocking the way cells of the nervous system transports biochemicals called “amines,” amitriptyline is able to increase the levels of circulating neurotransmitters, especially a neurotransmitter called “serotonin.” This mechanism seems to be at the root of amitriptyline’s anti-anxiety and psychoactive properties. In humans, this medication is used in the treatment of anxiety, bipolar disorders, and depression. This drug's serotonin modifying property is also responsible for its sedation side effect.
  • The same blockage of the amine pump leads to increased levels of the neurotransmitter “norepinephrine.” Norepinephrine is an important neurotransmitter in the “sympathetic” nervous system as described below.
  • Amitriptyline also has what are called “anticholinergic” effects which requires some explanation. The part of the nervous system which regulates an assortment of involuntary operations is called the “autonomic nervous system.” It is divided into two areas: the “sympathetic” system which is responsible for generating changes during a “fight or flight situation” (such changes include increased circulation to muscles, increased heart rate, pupil dilation etc.) and the “parasympathetic” nervous system which is responsible for maintaining the body’s “status quo.” The parasympathetic system uses “acetylcholine” as its chief neurotransmitter. An anticholinergic medication, disrupts acetylcholine and creates side effects such as dry mouth, urinary retention, constipation, dried respiratory secretions.
  • Amitriptyline is a strong antihistamine.

Amitriptyline is a member of the class of drugs called “tricyclic antidepressants.”


With amitriptyline becoming widely used in human mental illness, it was not long before small animal uses for this medication came to light. Amitriptyline has been used in animals for separation anxiety, for inappropriate urination in cats, for feline lower urinary tract disease in cats, and for obsessive grooming behaviors in both dogs and cats. In many of these conditions it is not clear which of the above described mechanisms of action are responsible for the desired effects.


The most common side effect is drowsiness/sedation.

Anticholinergic side effects would probably not be surprising: dry mouth (manifested in animals often as frequently licking of the lips), urinary retention, constipation.

The most potentially dangerous side effect that happens with a realistic frequency
is the exacerbation of a cardiac rhythm disturbance.
For this reason, an EKG screening has been recommended
before starting this medication.

Tricyclic antidepressants can alter blood sugar levels.

In humans, side effects in virtually every organ system have been reported at one time or another which means that potentially any side effect could be attributed to the use of this medication.


Tricyclic antidepressants such as amitriptyline cannot be safely used with monoamine oxidase inhibitors such as Deprenyl (Anipryl®).

The risk developing a dangerously low white blood cell count with the use of methimazole is greatly increased if there is concurrent use of amitriptyline.

The use of Cimetadine (Tagamet®) can interfere with the desired effect of amitriptyline.

Amitriptyline is best not used in conjunction with other drugs with anticholinergic effects, drugs that stimulate the sympathetic nervous system, or with other psychoactive drugs.

Use of the intestinal motility modifier cisapride leads to heart rhythm disturbances when it is combined with certain other medications. Amitripyline is one of those medications so these two drugs should not be used together.


Amitriptyline is removed from the body via the liver. Patients with abnormal liver function may have trouble with this medication. Periodic liver enzyme evaluation (blood testing) is a good idea for patients on this medication long term.

Amitriptyline should not be used in pregnancy or lactation, in patients with seizure disorders, or in patients with cardiac rhythm disturbances.

Diabetic pets should avoid the use of amitriptyline.

Page last updated: 9/28/2014