Didn't stop worms after Fluralaner + Moxidectin (Bravecto Plus) in cats

The FDA has received 119 reports of didn't stop worms in cats after Fluralaner + Moxidectin. That is 3.7% of all reports for this medicine, compared with 1.8% across reports for all cat medicines, so it is reported unusually often with this medicine.

119Reports
66%Marked serious
2.5%Recovered
0.8%Died or euthanised
20 daysTypical onset
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How soon it started

Same day
11 18%
1–2 days
0 0.0%
3–7 days
3 4.9%
1–4 weeks
26 43%
Over a month
21 34%

How the animals did

Recovered
2 1.7%
Recovered with lasting effects
1 0.8%
Still unwell when reported
108 91%
Euthanised
1 0.8%
Not known
7 5.9%

Problems reported at the same time

Age of the animals

Under 1 year
17
1–3 years
39
4–7 years
35
8–11 years
8
12+ years
5

About this medicine

Fluralaner kills fleas and ticks for up to 12 weeks (chewable or spot-on). Moxidectin prevents heartworm disease (monthly topical, or a 6- or 12-month injection for dogs).

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

In 2018 the FDA alerted owners and vets that isoxazoline products have been associated with neurologic reactions such as muscle tremors, wobbliness (ataxia) and seizures, including in animals with no history of them.

Questions owners ask

Can Fluralaner + Moxidectin cause didn't stop worms in cats?
119 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 20 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).

Didn't stop worms with similar medicines

All reported side effects of Fluralaner + Moxidectin in cats · Medicines most reported with didn't stop worms