At a glance
- Drug Name: Amitriptyline HCI
- Common names: Elavil, Amitrol, Endep, Levate, Laroxyl and Saroten
- Drug Type: Tricyclic Behaviour Modifier, Antipruritic, Neuropathic Pain Modifier
- Used For: Behaviour disorders, pruritis (itching), idiopathic cystitis, chronic neuropathic pain
- Species: Humans, cats, dogs, birds
- Administered: Tablet
What is amitriptyline?
Amitriptyline (am-e-trip’-ta-lean) is a prescription-only tricyclic antidepressant (TCA) that is sold under the brand names Elavil, Amitrol, Endep, Levate, Laroxyl and Saroten, it is used in both human and veterinary medicine.
Amitriptyline was discovered in 1960 and approved by the Food and Drug Administration for use in humans in 1961. The drug has not been approved by the FDA for use in cats but is commonly prescribed extra-label.
Amitriptyline is on the WHO Model List of Essential Medicines.
Uses
Amitriptyline is used to treat behavioural conditions in cats which include excessive grooming, spraying, urinating outside the litter box, pica and anxiety. It may also be useful for adjunctive treatment of pruritis, chronic neuropathic pain.
Mechanism of action
The exact mechanism of action is not known, but tricyclic antidepressants are thought to block the amine pump, thereby increasing neurotransmitter levels (especially serotonin and norepinephrine). Seratonin is responsible for feelings of well being and happiness. The same blockage of the amine pumps also leads to increased levels of norepinephrine which is an important neurotransmitter in the sympathetic nervous system.
Central and peripheral anticholinergic activity. Acetylcholine is a chemical messenger which transfers signals between certain cells in the body. Anticholinergic drugs block acetylcholine from binding to its receptors on certain nerve cells, inhibiting parasympathetic nerve impulses. These nerve impulses are part of the autonomic nervous system responsible for several functions not consciously controlled, which includes pupil dilation and constriction).
Other pharmacologic effects include stabilising mast cells via H1 receptor antagonism and antagonism of glutamate receptors and sodium channels.
Dosage
Behaviour disorders:
0.5 – 1 mg per kg, once per day or divided twice daily.
Pruritis:
The veterinarian may prescribe amitriptyline in cases where more conventional therapies have failed.
2.5 – 12.5 mg per cat once per day or 2.5 – 7.5 mg per cat twice a day.
Symptomatic therapy of idiopathic cystitis and FLUTD:
2.5 – 12.5 mg per cat once per day at night or 0.5 – 1 mg per kilo once a day at night.
In most cases, the veterinarian will prescribe 2.5 mg to 12.5 mg per day, and start at a lower dose, and gradually increase as tolerated. When discontinuing, the cat will be gradually tapered off.
Drug interactions
Inform the veterinarian if your cat is on any medications, some of the drugs listed below should not be prescribed to cats who are on amitriptyline, other drugs may be used in conjunction, but with close veterinary monitoring.
- Acetazolamide
- Alpha-2 adrenergic agnostics
- Amantadine
- Ammonium chloride
- Anesthetic agents
- Antiarrhythmics
- Anticholinergic agents
- Antihypertensive agents
- Anthracyclines
- Apomorphine
- Azole antifungals
- Barbiturates
- Benzodiazepines
- Beta-2 agonists
- Bethanechol
- Bromocriptine
- Buspirone
- Carbamazepine
- Cetirizine
- Cimetidine
- Cisapride
- Clonidine
- Cyproheptadine
- Desmopressin
- Diazoxide
- Divalproex
- Dobutamine
- Domperidone
- Estrogens
- Fluoroquinolone
- Hydroxychloroquine
- Ifosfamide
- Iohexol
- Leuprolide
- Levetiracetam
- Lithium
- Macrolides
- Methylphenidate
- Methylphenidate
- Metoclopramide
- Metronidazole
- Monoamine oxidase inhibitors
- Muscle relaxants
- Nitroglycerin
- Non-DHP calcium channel blockers
- NSAIDs
- Octreotide
- Opioids
- Pergolide
- Phenothiazines
- Phenytoin
- Physostigmine
- Potassium chloride
- Pregabalin
- Primidone
- Rifampin
- Rufinamide
- Selective-serotonin reuptake inhibitors
- Serotonin receptor antagonists
- Sulfamethoxazole
- Sulfonylureas
- Sympathomimetic agents
- Terbinafine
- Thyroid agents
- Tramadol
- Trazodone
- Valproic acid
- Vasopressin
- Warfarin
- Yohimbine
- Zonisamide
Contraindications
Do not administer amitriptyline to cats with a history of adverse effects to TCAs.
Use with extreme caution in cats with seizure disorders, as tricyclic agents may reduce seizure thresholds.
Use with caution in cats with liver disease, diabetes, glaucoma, cardiac rhythm disorders, adrenal tumours and keratoconjunctivitis sicca (KCS).
Side effects
The most common side effects are sedation, urinary retention and diarrhea. Other side effects can include ataxia (wobbly gait), thrombocytopenia (low blood platelets), nausea and vomiting, hypersalivation (drooling), neutropenia, unkempt coat, disorientation and heart conductivity disorders.
Always inform your veterinarian if your cat develops side effects, it may be necessary to reduce the dose.
Storage
Store at room temperature away from children and pets.
Frequently asked questions
How long does it take for amitryptiline to work in cats?
It takes between 7 – 10 days for amitryptiline to reach full therapeutic effect. Sedation effects may develop when the cat starts amitryptiline, but should not be confused as a response to treatment.
Does amitryptiline need to be given with food?
No, amitryptiline can be given with or without food.
Can amitryptiline cause constipation in cats?
Yes, amitryptiline can cause constipation in cats due to its anticholinergic properties.
How is amitryptiline supplied?
Amitryptiline comes in tablet form but can be compounded into a liquid or paste by a compounding pharmacy.
Resources
Plumb, D.C. (2018). Veterinary drug handbook. Ames, Iowa: Iowa State Press.
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