Didn't prevent heartworm after Fipronil + S-methoprene (Frontline Plus) in dogs

31 reports to the FDA describe didn't prevent heartworm in dogs given Fipronil + S-methoprene. That is 1.0% of all reports for this medicine, compared with 13% across reports for all dog medicines, so it is reported less often than average with this medicine.

31Reports

23%Marked serious

13%Recovered

0.0%Died or euthanised

–Typical onset

How the animals did

Recovered

1 3.2%

Recovered with lasting effects

3 9.7%

Still unwell when reported

4 13%

Not known

23 74%

Problems reported at the same time

Cardiac disorder

5 16%

Didn't work as expected

3 9.7%

Vomiting

2 6.5%

Leucocytosis

1 3.2%

Eosinophilia

1 3.2%

Seizures

1 3.2%

Weight gain

1 3.2%

Drug dose omission

1 3.2%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Fipronil kills fleas and ticks (spot-on).

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

Questions owners ask

Can Fipronil + S-methoprene cause didn't prevent heartworm in dogs?: 31 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.
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 prevent heartworm with similar medicines

Didn't prevent heartworm after Spinosad (Comfortis) 99 reports · 0.2% of its reports
Didn't prevent heartworm after Lufenuron + Milbemycin Oxime (Sentinel) 7,458 reports · 29% of its reports
Didn't prevent heartworm after Imidacloprid + Moxidectin (Advantage Multi) 1,665 reports · 13% of its reports
Didn't prevent heartworm after Nitenpyram (Capstar) 30 reports · 0.3% of its reports
Didn't prevent heartworm after Lufenuron + Milbemycin Oxime + Praziquantel (Sentinel Spectrum) 2,544 reports · 26% of its reports
Didn't prevent heartworm after Flumethrin + Imidacloprid (Seresto) 62 reports · 2.7% of its reports
Didn't prevent heartworm after Fipronil 30 reports · 2.1% of its reports
Didn't prevent heartworm after Imidacloprid + Permethrin 20 reports · 4.3% of its reports

All reported side effects of Fipronil + S-methoprene in dogs · Medicines most reported with didn't prevent heartworm