I know it goes without saying, but prevention is the best method here. Dogs like to be repeat offenders, so try to be sure that the weed is put somewhere he cannot access it. They typically don't learn from their mistakes in cases like these and he's apt to do it again.
That being said, most dogs who consume weed usually survive although they often exhibit signs of being stoned, basically. We often see hard sleeping, balance issues when walking, urinating while sleeping, easily startled behavior, low temperature, etc. It's customary to recommend taking your pet to the vet as they can induce vomiting, monitor symptoms/temperature and administer activated charcoal to minimize absorption in the GI tract for what may have made it out of the stomach. This is the safest approach.
If you choose to keep him at home, keep an eye out for more major symptoms such as being unable to wake him, seizures, vomiting, diarrhea, non-responsive behavior, if he stops breathing, etc. The majority of symptoms occur within the first 12-24 hours of consumption and he should be resolved by the 72 hour mark. If he worsens, you absolutely must take him to a veterinarian this evening. It may be worth finding an ER clinic just in case you need it. If you need assistance with this, reply with your city, state and zipcode and I'll locate one for you.
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