My dog ate 300mg of isoniazid?

Yesterday morning my mom dropped a pill, didn't bother looking for it, and it didn't even cross her mind that the dog might eat it. She also didn't tell me about it, until after 6pm last night, when the dog started wobbling when she walks and shaking. The vet was already closed. She seemed herself apart... show more Yesterday morning my mom dropped a pill, didn't bother looking for it, and it didn't even cross her mind that the dog might eat it. She also didn't tell me about it, until after 6pm last night, when the dog started wobbling when she walks and shaking. The vet was already closed. She seemed herself apart from the tremors, so I took her to the vet this morning. They said they wont look at her, and the receptionist gave me a list of emergency numbers to call.
I don't have thousands of dollars just to take her in, not guaranteed they help her at all.

I'm not looking for lectures, on how I should have taken my dog to an emergency vet last night, or criticism that if I don't have money for emergencies I shouldn't own a dog. I'm here looking for advice, so if you're not gonna help, please don't answer.

It's been about 24 hours now since she likely ate the pill, she's been acting, eating and drinking fine. She's not stumbling much, but she's still a little shaky. I've been giving her milk to try to flush it out.

I know isoniazid is highly toxic to dogs, but at what dosage? She only ate one pill, even though it's 300mg.

She's an 8 month old german shepherd/american eskimo mix. About 50 pounds.

Is there anything I can give her to help?

Please and thank you.
Update: The only ER places on that list in my area are hospitals. One with terrible care, and another one which only wants your money. Which I know for a fact would charge me up to and over a thousand for various tests not even related. I found another vet that is open and called, they said they'll take her in... show more The only ER places on that list in my area are hospitals. One with terrible care, and another one which only wants your money. Which I know for a fact would charge me up to and over a thousand for various tests not even related.

I found another vet that is open and called, they said they'll take her in immediately. Got bloodwork done, and everything looks fine. Vet said that Isoniazid is used in dogs, and is usually given at 10 mg per pound. She got a 13mg dose. Since it's already been 24 hours, she isn't showing any serious symptoms, and all her bloodwork is fine, it isn't likely it would start to decline now, but I should watch her.

Thank you for your help, for those who offered some advice.

The true negligence should go to my regular vet, because I came in with a poisoned dog, and they said oh sorry! we're full, not our problem!
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