My dog ate human cold medicine. Is it an emergency? He's lethargic.
Hi, and thank you for your question on Petco Pet Education Center, formerly Petcoach! This particular medication has two medications that should be fairly well tolerated by dogs but can cause mild sedation as it contains an antihistamine and dextromethorphan. Phenylephrine, however, could be toxic due to cardiac side effects. Also, there may be sweeteners such as xylitol which is highly toxic to dogs.
My recommendation would be to call the ASPCA poison control at (888) 426-4435 and make a visit to the vet as soon as you can with Happy this evening as he could be experiencing side effects of the medication or have a different problem entirely. Coughing in the first place is worrisome as older dogs are highly prone to heart problems which can lead to both the cough and the lethargy.
I hope this helps, and I hope Happy gets better soon!
Updated on September 23rd, 2025