The regurgitation of his food, high volume of water consumption and the vomiting all suggest that Zach has a pretty substantial GI upset. I can give you some things to try at home, but if his symptoms don't improve quickly he will need to see a vet for diagnostics and injectable medication to be administered. There are a variety of causes including the ingestion of things that may have upset his stomach such as human food, leaves, sticks, etc. to more major concerns like gastric blockages due to consuming part of a toy, a bone, etc.
The first step is to administer a dose of regular pepcid (famotidine) every 12-24 hours. You will want to give 0.5mg/pound of body weight (a 10# ***** would receive 5mg, a 5# ***** would receive 2.5mg, etc). For this, you can visit any human pharmacy and buy the OTC brand name Pepcid, or you can use the cheaper, off-brand “famotidine” that’s available. Either will be useful.
2 hours following a dose of famotidine, the time needed for the medication to begin working, you can offer a bland diet. To make this, you’ll combine white or brown rice, boneless, skinless chicken breast and sufficient water for cooking in a stock pot. Boil on medium until it turns to mush and the breast is easily flaked. To avoid more nausea, start with small amounts to begin with and offer the amount every 2-4 hours. A few teaspoons to start is typically sufficient and you can work your way up every 2-4 hours in incremental increases until you’re sure no vomiting will be seen. If your companion requires a more palatable food, try adding in pureed baby food in chicken, turkey and similar flavors. Avoid those that contain onion or garlic in the ingredient panel.
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