it is probably safe to give melatonin on cats. however, medicaiton is not the only thing that will help in your case. Melatonin is usually used in cats for nocturnal vocalization, and anxiety, not for aggression. It may also be hard to give melatonin form a supplements, since the dose is made for humans and not cats. You may need to have it compounded by a pharmacist.
If we discuss about melatonin, it has many regulatory and immune modulating functions. Proper melatonin levels regulates circadian rhythm in the hypothalmus. It appears to decrease depression and it has potent central nervous system antioxidant effects. It has some clinical applications in skin alopecias (hair loss) as well.
Melatonin may regulate growth hormone secretion during sleep (involving rapid eye movement) and may even stimulate bone cells through its action on growth hormone (GH).
Behavior and systemic effects of this chemical are extensive. Sleep disorders, depression and hair loss are routinely treated with melatonin.
When you have aggression, several medication can be used, but you always need to be address the primary problem. Aggression because the aggressive cats, feel there is one too many in the household. in nature, care are naturally solitary and after weaning kittens usually go their own way.
You can try some natural remedy like Nutri-calm available at your primary care veterinarian from Rx Vitamins.
Here is a link about introducing a new kitty.
Let me know if you need additional information, or have more questions.
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