How Long does Prozac take to work in cats?

When your cat starts to become overly aggressive and starts to have a little too many ‘accidents’ outside the litter box, then it may be time to consult a pet behaviour specialist or a vet. However, if you have other cats or have previously experienced your cat’s behaviour changes, you know that many vets recommend using a medication called Prozac. While the process should be quite straightforward, exactly how long should Prozac take to work in your cat?

If you are unsure about this, keep reading because, in this article, we will answer this question and how you can use Prozac to ease your cats’ behavioural problems.

How Long does Prozac take to work in cats?

How long does Prozac take to work in cats?

Since Prozac deals with certain parts of the brain that handle behaviour controls of the body, you must have an estimate of how long the medication has to continue.

This is because, if it heals the cat soon, then the cat has to be weaned off of Prozac as soon as possible, if not, the medication has to be continued with the dosage being adjusted every once in a while.

Generally, though, Prozac takes about 1.5 to 2 months before you notice any visible behaviour changes in your cat. In less severe cases, it can take less time, but for that, your vet can guide you better.

As for regular and severe cases, the medication can take a good amount of time to cause healing and changes in behaviour, so don’t be disheartened and leave the medication before the course ends.

Moreover, every cat is different. Just because Prozac fixed one cats’ behavioural problems in a short period, doesn’t mean it will fix your cats too.

The pace of any visible behavioural changes in your cat’s behaviour depends on a variety of factors such as:

  • Breed of your cat
  • Previous health issues like kidney, heart, liver problems
  • Age of your cat
  • Toleration level
  • Proper dosage given

Prozac has been effective for around 90% of cats to fix their behavioural issues. Such as prozac is used for aggression. So as long as you give it for the due period, you will observe behavioural changes.

Have you been giving prozac on alternate days? If you dont observe changes in the prescribed period, then you must consult your vet about this matter.

Signs that Prozac is not working in your cat

A valid question that is asked by many cat owners when beginning to use Prozac for treatment is how to figure out if Prozac is working in their cats at all.

As a general rule of thumb, you should always thoroughly look into medications that affect the brain before ingesting them.

As for Prozac, the effects of Prozac not working in your cat can be clearly visible soon enough, but they don’t always appear in every cat.

There are different signs you can look out for to see if Prozac is not working in your cat, such as:

  • Lethargy in your cat
  • Constant diarrhoea and vomiting
  • Loss of weight in your cat
  • Breathing problems

The more serious set of signs after which you should go to the vet for a change in medication/dose can be:

  • Seizures
  • Heartbeat increase
  • Increasing anxiety and stress
  • Vomiting but in a larger amount
  • Heart, liver or kidney failure
  • Difficulty in sleeping for days on end

It should be noted that all this is important to know because Prozac is a strong antidepressant. With medications like these, it is best to know how long they take to benefit your pet, otherwise, you will notice side effects like these.

Plus, the longer you continue the medication without it being needed by the cat’s body, the more it won’t work, so please do not take this matter lightly.

While you may notice behaviour changes in your cat a few weeks after giving Prozac if you find any signs of it not working, take your cat to the vet.

How to avoid overdosing in a bid to make Prozac work quicker

When you come from the vets’, you should have a proper prescription stating what dosage of Prozac is fit for your cat to consume.

If you don’t have this, we highly suggest that you consult your vet about this again, because, with antidepressants, you want to avoid an overdose as much as you can.

We’ll give you an idea about what Prozac dose is given to cats, but keep in mind that this is not personalized advice for any cat. It also does not replace veterinary advice whatsoever.

After consideration of all the factors that will decide on the dose of Prozac for your cat, most cats require 2 to 4.5 mg of Prozac per day.

Sometimes, people are impatient and want to reduce the course of the medication. In this case, their doctor recommends to take Prozac every other day, but the dose is reduced.

But often times, people end up overdosing Prozac in this case too.

To avoid overdosing, all you have to do is read the marking of the instrument properly, and make sure the reading is exactly what the doctor said to give your cat.

Other than this, if you have any questions about the dose, mention your concerns to a doctor and he’ll guide you so you don’t overdose Prozac even slightly.

This has to continue for 6-8 weeks, and hopefully, by then you will see a change in your cats’ behaviour and overall mental health as well.

What should you do if Prozac does not work in your cat at all?

If you see some of the signs of Prozac not working in your cat as we mentioned above, then its time to look into some alternate options. There is only so long you can wait to see if a medicine is working for your cat or not.

The first thing is to make sure that you have tried the dosage variations as recommended by your vet on your cat.

You want to be certain that you’ve tried everything with Prozac, because switiching too many antidepressants can mess up with hormones in the cats body.

Once you are sure about this, you should move to the next step.

As you know, fluoxetine is the name of the antidepressant which comes in different brands. So if Prozac is not working for your cat whatsoever, you should give another fluoxetine brand a try.

Who knows, it might suit your cat and fix its behavioural problems better than Prozac did.

Lastly, talk to your vet about the right alternatves for your cat. They will suggest you the best advice that will be beneficial for your cat.


In conclusion, Prozac is a good medication for behavioural problems in cats, but exactly how long does Prozac take to work?

It takes around 6-8 weeks for Prozac to cause a change in the behavioural properties of a cat. Even after then, in many serious cases of aggression in cats, the treatment can be prolonged, so there is no definite period for all cats.

The effect of the medicine does not last very long in the short term and a new dosage has to be given a few times a day to keep your cat healthy.

Your vet will show you how the medication has to be given so it can benefit your cat as much as possible, and it does not have to stay on treatment for as long.

Moreover, take care of providing the right dosage to your cat. This is because not only can an overdose prolong the treatment further, but also negatively impact your cats’ mental health.

Finally, if you feel like Prozac is not working in your cat after lookin gat the signs we mentioned above, make sure you talk to a vet immediately.

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