Drug dose administration interval too long after Ivermectin + Pyrantel (Heartgard Plus) in dogs

The FDA has received 874 reports of drug dose administration interval too long in dogs after Ivermectin + Pyrantel. That is 0.6% of all reports for this medicine, compared with 0.3% across reports for all dog medicines, so it is reported unusually often with this medicine.

874Reports
57%Marked serious
5.7%Recovered
0.5%Died or euthanised
71 daysTypical onset
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How soon it started

Same day
5 2.3%
1–2 days
2 0.9%
3–7 days
2 0.9%
1–4 weeks
9 4.2%
Over a month
197 92%

How the animals did

Recovered
26 3.0%
Recovered with lasting effects
24 2.7%
Still unwell when reported
124 14%
Died
1 0.1%
Euthanised
3 0.3%
Not known
696 80%

Problems reported at the same time

Age of the animals

Under 1 year
97
1–3 years
356
4–7 years
257
8–11 years
120
12+ years
36

About this medicine

Ivermectin prevents heartworm disease (monthly). Pyrantel treats roundworms and hookworms.

Products with this combination include Heartgard Plus, Tri-Heart Plus, Iverhart Plus. 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 Ivermectin + Pyrantel cause drug dose administration interval too long in dogs?
874 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 71 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).

Drug dose administration interval too long with similar medicines

All reported side effects of Ivermectin + Pyrantel in dogs · Medicines most reported with drug dose administration interval too long