Pet owners can sometimes encounter overly aggressive behavior from their pets. And it would be good if this problem were always solved by training or other mild methods of behavior correction. However, there are also such severe and untreatable cases that one may consider abandoning the pet or even resorting to euthanasia. Of course, one should not rush with such a decision because if the situation is so bad, there is no reason not to try another option, which is to restore the normal functioning of the “violence inhibitor” with the help of medications.

It is known that the main regulator of aggressive behavior in animals is the serotonergic system of the brain (the same is true for humans, in which case it is also called a violence inhibition mechanism). The disruptions in its function lead to pathological expressions of aggression, and enhancing its function has an anti-aggressive effect^[1]. Accordingly, it is necessary to look toward agents that positively affect the function of this system.

You can start by using supplements with tryptophan, a precursor to serotonin. This is a highly safe approach in terms of side effects and risk of overdose. In one study, daily supplementation with 1.45 grams of tryptophan per kilogram of animal weight in dogs' diets resulted in a significant reduction in their aggressiveness after just one week^[2].

Natural remedies that target specific receptors of the serotonergic system should also be safe. In laboratory experiments on mice, the herbal extract mixture Kamishoyosan (also known as Jia Wei Xiao Yao San in Chinese) has shown promising results. Its daily administration in a dosage of 100 milligrams per kilogram of weight should have an anti-aggressive effect. The Yokukansan herbal extract mixture, or even its single component, Uncaria rhynchophylla extract, should also be effective. Daily administration of 0.5–1 g/kg of Yokukansan or 75–150 mg/kg of Uncaria rhynchophylla extract should be sufficient^[3][4].

If natural remedies do not have the desired effect, you can consider more serious options. Start with triptans, commonly used against migraine. Especially worth mentioning is zolmitriptan, which demonstrated an excellent anti-aggressive effect in laboratory experiments on mice as well as high safety of administration, including to dogs^[5][6]. You can start with a dosage of 1 mg/kg per day. However, given the safety of the drug, we will not exclude the possibility of increasing this dosage if necessary.

Selective serotonin reuptake inhibitors (SSRIs), which are classical antidepressants, are also effective. As one study shows, in the case of aggressive dogs of various breeds, fluoxetine (Prozac) may be a good option. Its daily administration at a dosage of 1.5 mg/kg resulted in a significant anti-aggressive effect a month after the start of therapy, and six months later, there was practically nothing left of the previous aggressiveness. At the same time, no toxic effects were observed during the experiment^[7]. Another study on the administration of fluoxetine to dogs at a dosage of 1 mg/kg per day also demonstrated the presence of a significant anti-aggressive effect as early as 3 weeks after the start of therapy^[8]. A similar approach can be used in aggressive cats: daily administration of fluoxetine at a dosage of up to 1.5 mg/kg^[9].

Of course, SSRIs are known for causing unwanted side effects. They are also not recommended for use if the pet has specific health problems, such as seizures. Therefore, instead of using SSRIs, which lead to a general increase of serotonin levels in the brain, it is worth trying agents that affect specific receptors (1A and 1B) of the serotonergic system, such as the previously mentioned herbal extracts or triptans. Although such drugs have so far been tested for an anti-aggressive effect only on laboratory animals (mice and rats), the result, which is the elimination of offensive aggression without causing any side effects, is impressive.

When administering any of the mentioned medications, it is important to ensure that the pet takes the full dosage. Animals may refuse to eat food containing some drugs due to the bitter taste or specific odor. It is advisable to put the drug in a large amount of food to reduce discomfort for the animal. But it is also necessary to make sure that there is no overdose, which, in the case of some drugs (especially SSRIs), can be dangerous for the pet's health. And in case of side effects, you should immediately stop using the drug that caused them and consider other options!

We hope this material will help you solve the problem of aggressive pet behavior if it occurs. At the very least, it is definitely worth trying the approach suggested here if there are no alternatives left because it may be the one that will work best in your case.

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