Hello, I am Dr. Zoe, a licensed veterinarian here to help. This sounds extremely concerning for Smoke. I first must ask if Smoke received a full vaccination series for parvovirus (in the distemper vaccination) done not at home or by a breeder but by a vet. If so, then we can probably safely rule out parvovirus as the cause of his signs. If not, then I am worried that he could have parvovirus...and this is not something that he will survive with the signs you report with at-home care only. Even if you try at-home care you are going to need a veterinarian's assistance to provide medications and fluids to try to help him. This carries a very poor prognosis with at-home care, though (high percentage will die) and really does require hospitalization with IV fluid therapy and treatments.
If we are entirely sure this is not parvovirus then again this is concerning and the possible underlying causes can range from severe intestinal worms to ingestion of an inappropriate item that is stuck to organ issue (liver, kidney).
About the only things I can recommend you can do OTC other than offer the syringe of an electrolyte solution (Pedialyte for kids is better than Powerade) is:
1)Give famotidine 10mg 1 tablet every 12 hours (Pepcid AC) - can get at any pharmacy for people; helps with nausea
2)Offered a bland diet of white rice and boiled chicken breasts
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