Thanks very much for the additional information.
I am glad to hear he did not eat the bait station, that is one less worry, and that he is his usual annoying self!
The ingredients in Trifexis (spinosad + milbemycin oxime) should not interact with that particular toxin. In fact some products to kill fire ants combine spinosad & Hydramethylnon.
Hydramethylnon is a trifluoromethyl aminohydrazone insecticide. It is poorly absorbed from a dog's gastrointestinal tract, more than 95% is excreted in the stools and not absorbed.
The most common signs reported in dogs with oral ingestions of hydramethylnon are gagging and vomiting. But we only need to induce vomiting if large amounts (greater than 1 ounce of bait per kilogram or body weight or 0.45 ounces per pound of body weight are ingested. That means if a 26 pound dog eats less than 11.7 ounces of hydramethylnon he should not get sick.
According to the manufacturer of Combat Roach Control System (1.65% hydramethylnon) a medium-sized (4.545 kg or 10 pound) dog would experience adverse effects from the bait itself only after eating an amount equivalent to 50 trays. The amount he ate by eating one trap was even less, and he weighs much more. That means he should not get sick.
Please let me know if you have any further questions.