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Dr. Braha
Dr. Braha, Veterinarian
Category: Cat Veterinary
Satisfied Customers: 388
Experience:  Veterinarian
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how long after giving my cat Mirtazapine would it start working

Resolved Question:

how long after giving my cat Mirtazapine would it start working and make her hungry to eat?
Also, I heard that B-12 or one of the B vitamins stimulates a cats appetite. Is this true?
Submitted: 4 years ago.
Category: Cat Veterinary
Expert:  Dr. Braha replied 4 years ago.

Thank you for posting your question can you also provide me with some more information as to:


How much Mirtazapine (dose) she is receiving?

Is this her first time being administered the drug?

What underlying condition does she have making her not want to eat?

How frequent have you been instructed to administer the medication?

Customer: replied 4 years ago.

I don't know the miligrams, but the dose is 1/4 a tablet every 3 days if needed. This would be the second time she would be taking it.


The first time she had to use it was after she came back from the vet after having a depostation. The vet said she lost her appetite due to the medication she was given that day. I used the mirtazpine only once that night and then her appetite resumed in full force.


Then we had to bring her back to the vet yesterday a second time this week just to be checked out and being a normally nervous cat, I think the stress of visiting the vet so soon after last week made her even more stressed and when she's stressed she doesn't want to eat.

Expert:  Dr. Braha replied 4 years ago.
Thank you for providing all the additional information. I am glad to hear that her loss of appetite is a sporadic occurrence and likely stress related compared to having an underlying condition. She is currently receiving 3.75mg which is the high end of the dose so if you are not seeing any immediate response to the medication there is no "play room" to increase her dose for the time being. That being said new research has shown that it can be repeated in 48 hours instead of waiting the entire 3 days. Once the tablet is given the drug is being absorbed into her drug stream within the hour. At this point the drug should start to have an effect but will reach maximum concentrations in her blood a few hours later and provide your cat back with her appetite at this point. You are correct in the fact that vitamin B12 does have appetite stimulating properties although this is not the first choice in helping a cat with a poor appetite. It is generally used in cats with long term diminished appetites by administering an injection of the vitamin B12 under their skin once a week.
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