15.May 2022

Melatonin in veterinary medicine


The main function of the hormone melatonin is the regulation of the day and-night rhythm. In daylight, the production is inhibited, in darkness stimulated - the melatonin production shows accordingly also seasonal variances, whereby, among other things, the seasonal change of coat is stimulated and  it can be used in some forms of alopecia (stimulation of the anagen rate).

Melatonin production decreases with age, providing a possible bridge to its use in senior dogs.

In general, there are few conclusive studies for the use of melatonin in veterinary medicine; but most of the knowledge is based on practical experience. Isolated studies have looked at its use in epilepsy (anticonvulsant effect in nocturnal seizures), but conclusive scientific studies on this topic are lacking to date.

Known indications for the use of melatonin

→ Dosage data are to be understood as guidelines and may need to be adjusted individually.

  • Anesthesia: According to a 2020 dissertation, preoperative use of melatotin (5mg/kg p.o. 2 h before induction of anesthesia) leads to a more relaxed behavior of dogs as well as a reduced use of propofol.
  • Dermatology: alopecia X or follicular dysplasia: different data on dosage are available: 2-4 mg/kg or 3-6 (12) mg/animal 1-3x daily for about 2-3 months, depending on the author. Used with either high or lack of success.
  • Canine pattern baldness (stencil disease)
  • Canine recurrent flank alopecia: Improvement can be expected after 1-3 months.
  • Color dilution alopecia : 1.5-6 mg 2-3x daily.
  • Preventive administration (3-6 mg 1-2x daily), starting about 4 weeks before possible onset of hair loss, can also be used with partial success in some forms of follicular dysplasia.
  • Hyperadrenocorticism: melatonin as an "antagonist" of cortisol, helps stimulate hair growth in Cushing-induced alopecia. Possibility to lower the cortisol levels but more detailed studies are missing. Successful reports of joint use with lignans (sec. plant compounds) in atypical Cushing's exist. Possible dosage: 1-6 mg (depending on dog size) 2x daily.
  • Sexual behavior: In the USA, melatonin is used as a neutering chip for male and female cats, especially liked temporarily in breeding cats, because the later suitability for breeding is preserved. In Europe, the Vetmeduni Vienna has also worked on this method: The chip is placed between 2 heatings and suppresses the next heatings for 3-4 months. The implant can also be given after birth, repetitive application is possible. However, it must be mentioned that the effect and duration of action are not absolutely reliable and the implants are not currently available in Europe according to current knowledge.
  • Behavior: Pronounced noise anxiety (1.5-6 mg depending on dog size) and age-related nocturnal restlessness or anxiety disorders (e.g., in canine cognitive dysfunction). Nocturnal restlessness in cats: 3-12 mg/animal p.o. 1-2x tgl.

The long-term effects as well as possible interactions with sex hormones have not been sufficiently researched in either human or veterinary medicine, which is why the permanent administration of melatonin should only be carried out after thorough consideration.

Melatonin has a relatively short half-life, so it should be taken once a day, preferably 1-2 hours before bedtime. Measurements from human medicine showed that the bioavailability as well as the onset of action is reduced or delayed in case of simultaneous intake with food, which is why melatonin should preferably not be given with food.


In human medicine, there are drugs approved for sleep disorders in the elderly population. There are also some over the counter medications in pharmacies, which are often used against jetlag, for example.
In Germany, there is currently no approved veterinary product available containing melatonin. Should your customers buy melatonin in the pharmacie, it must be ensured that they contain no xylitol!
In the USA, the use of melatonin is more common and a variety of preparations with sometimes higher dosages are available on the market for both human and veterinary medicine.

Known side effects and contraindications

Both human and veterinary medicine lack extensive studies on side effects, interactions, or contraindications, but melatonin has so far been described as having very few side effects.

However, the following should be mentioned:

  • From human medicine are known drowsiness and concentration problems. However, this can be counteracted by taking it at the correct time (in the evening) and not using it continuously. Headaches are also mentioned as a side effect.
  • Influence on sex hormones and fertility: Therefore, use only in adult dogs or cats that are not pregnant or used for breeding.
  • Metabolism is largely via the liver, therefore avoid use in hepatopathies if necessary.
  • No reliable values are available for use in renal insufficiency.
  • The possible influence on thyroid hormones should be monitored.

Drug interactions

Melatonin may potentiate the effects of benzodiazepines or succinylcholine when administered simultaneously.


Determination of melatonin blood levels is not yet possible in current laboratories and reference values are not available.




Bibliography: Upon request

Author of the article:

Veterinarian vet. med. Julia Brüner