Didn't prevent heartworm after Moxidectin (ProHeart 6) in dogs

The FDA has received 11,529 reports of didn't prevent heartworm in dogs after Moxidectin. That is 23% of all reports for this medicine, compared with 13% across reports for all dog medicines, so it is reported unusually often with this medicine.

11,529Reports

66%Marked serious

2.0%Recovered

0.5%Died or euthanised

283 daysTypical onset

How soon it started

Same day

60 1.6%

1–2 days

11 0.3%

3–7 days

7 0.2%

1–4 weeks

33 0.9%

Over a month

3,591 97%

How the animals did

Recovered

231 2.0%

Recovered with lasting effects

2 0.0%

Still unwell when reported

9,653 84%

Died

44 0.4%

Euthanised

19 0.2%

Not known

1,580 14%

Problems reported at the same time

Didn't work as expected

813 7.1%

Medication error

537 4.7%

Drug dose administration interval too long

403 3.5%

Drug dose administration interval too short

243 2.1%

218 1.9%

145 1.3%

78 0.7%

57 0.5%

Age of the animals

Under 1 year

1–3 years

6,497

4–7 years

3,241

8–11 years

1,239

12+ years

285

About this medicine

Moxidectin prevents heartworm disease (monthly topical, or a 6- or 12-month injection for dogs).

Products with this ingredient include ProHeart 6, ProHeart 12. The FDA hides brand names in its public data, so these reports cover every product with the same active ingredients.

Some herding breeds (for example Collies) carry the MDR1 gene variant and can be more sensitive to this drug class at high doses.

Questions owners ask

Can Moxidectin cause didn't prevent heartworm in dogs?: 11,529 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 283 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 prevent heartworm with similar medicines

Didn't prevent heartworm after Ivermectin + Pyrantel (Heartgard Plus) 57,581 reports · 39% of its reports
Didn't prevent heartworm after Milbemycin Oxime + Spinosad (Trifexis) 10,801 reports · 8.3% of its reports
Didn't prevent heartworm after Milbemycin Oxime + Praziquantel (Interceptor Plus) 8,433 reports · 27% of its reports
Didn't prevent heartworm after Milbemycin Oxime (Interceptor) 13,118 reports · 44% of its reports
Didn't prevent heartworm after Selamectin (Revolution) 8,789 reports · 30% of its reports
Didn't prevent heartworm after Ivermectin (Heartgard) 3,385 reports · 28% of its reports
Didn't prevent heartworm after Ivermectin + Praziquantel + Pyrantel (Iverhart Max) 1,879 reports · 22% of its reports
Didn't prevent heartworm after Moxidectin + Pyrantel + Sarolaner (Simparica Trio) 319 reports · 28% of its reports

All reported side effects of Moxidectin in dogs · Medicines most reported with didn't prevent heartworm