Ivermectin (Heartgard) side effects in Mastiffs

54 FDA reports involve Ivermectin in a Mastiff. These are the problems they describe.

Didn't prevent heartworm
17 31%
Vomiting
14 26%
Didn't work as expected
6 11%
Lethargy
6 11%
Wobbliness (ataxia)
4 7.4%
Eye or vision problems
4 7.4%
Didn't stop fleas
3 5.6%
Tremors
3 5.6%
No sign
3 5.6%
Loss of appetite
3 5.6%
Blood problems
3 5.6%
Labeled drug-species interaction
2 3.7%

All reports for Ivermectin in dogs