Hyperphosphataemia after Mirtazapine (Mirataz) in cats

The FDA has received 22 reports of hyperphosphataemia in cats after Mirtazapine. That is 1.2% of all reports for this medicine, compared with 1.0% across reports for all cat medicines.

22Reports

91%Marked serious

0.0%Recovered

45%Died or euthanised

10 daysTypical onset

How soon it started

Same day

1 5.0%

1–2 days

6 30%

3–7 days

3 15%

1–4 weeks

4 20%

Over a month

6 30%

How the animals did

Still unwell when reported

11 50%

Died

3 14%

Euthanised

7 32%

Not known

1 4.5%

Problems reported at the same time

21 95%

15 68%

12 55%

10 45%

10 45%

Elevated symmetrical dimethylarginine (sdma)

9 41%

Lethargy

7 32%

Vomiting

7 32%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Mirtazapine stimulates appetite (cats: ointment applied to the ear).

Products with this ingredient include Mirataz. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

Questions owners ask

Can Mirtazapine cause hyperphosphataemia in cats?: 22 reports link the two, but a report alone does not prove the medicine was the cause: other illnesses, other medicines or coincidence can be involved. Your vet can judge it for your animal.
How soon after a dose was it reported?: In half of the reports with dates, it started within 10 days of the first dose.
What should I do?: Don't give another dose until you've spoken to your vet, and keep the packaging so you can tell them the product and dose. Your vet can also report it to the FDA (or you can, through the manufacturer or FDA form 1932a).

Hyperphosphataemia with similar medicines

Hyperphosphataemia after Maropitant (Cerenia) 114 reports · 3.0% of its reports

All reported side effects of Mirtazapine in cats · Medicines most reported with hyperphosphataemia