I'm sorry to hear about your girl - I have a min pin too, and they're just wonderfully peppy dogs!
It's certainly possible that your girl has periodontal disease - this can cause a host of problems throughout the body. But I wonder if she doesn't have another parallel problem going on as well.
I wonder if your girl could be suffering from seizures. The stumbling and the urination during these "episodes" sounds like a classic petit mal seizure. Was this occurring before she started the antibiotics? You can see some pets react adversely to medications, and seizures can be among the symptoms.
It's very possible that your dog could be otherwise healthy and still have a seizure disorder. They can also arise seemingly out of nowhere, so even if he has no history, this is a possibility.
Petit mal seizures, for instance, can involve spasms, episodes of staring off into space and bouts where the dog loses coordination. The mention of these spasms stopping him in his tracks is really consistent with these seizures. What really sets these apart from grand mal seizures is that the dog maintains control over certain parts of the body, so some of these seizures can be very subtle. It's even possible that he's been having them for years and you just didn't realize it.
To learn more about canine seizures, you can visit these sites - they have some really helpful information on the different types of seizures and what you can do when these occur. Hopefully, in reading some of the descriptions, something will "click" and make sense for you:
These website links will take you to a site that lists some of the other symptoms of seizure and the different types of seizure:
As for the other symptoms, it's possible she could be suffering from an upset stomach too. My min pin is VERY prone to stomach problems (she actually had a special surgery to pin her intestines in place because she was developing chronic bloat! Very rare in small dogs).
Her lethargy could be due to not eating and drinking properly, although the nutri cal should help with that. If she's in pain due to a problem with her teeth, a soft food may help. And if her stomach is upset, a bland food could be beneficial, so we'll want to try her on some bland people food.
You'll want to offer a small meals of bland food (rice, cottage cheese, chicken, hamburger, as discussed above). In the cases of the meats, be sure to drain and cut away any fat. The key is to keep these foods light on the stomach. To start out, only offer one or two spoonfuls. If she keeps this down for four hours, offer a bit more than you did the first time. Wait another four hours and repeat the process until you get up to about 1/4 or 1/3 of her normal meal size. And feed her this food three or four times a day for two full days. On the fourth day, you can begin to feed her normal dog food. But don't do this changeover suddenly. Mix four parts of the bland food with about one part normal dog food. On the fifth day, mix three parts bland food to two parts normal dog food and continue at this rate until she's back on her normal dog food.
Notably, this bland food will be more appealing to her than her normal food, so she may be more apt to eat this, even with a stomach ache or tooth ache.
You could also try to hand feed her, in the event that a bad tooth is at the root of this problem.
ix her food with water to make a mush. Use a blender, if necessary. If she's on dry food, add hot water and wait until the kibble swells, then mash it up and add a bit of water, if necessary. Using a liquid syringe can be an effective way to feed her - just don't aim for the back of the throat, as she could aspirate the food into her lungs. Instead, aim for the side of the mouth, more near the back. This will help bypass her teeth and avoid some of the discomfort if a tooth is to blame.
You can find liquid syringes at the pharmacy counter (just ask for one, they're usually free at places like Walgreens) or you can buy one - they're found in the baby section, as they're used to give medicine to babies. I recommend the type that are like a plunger, rather than the type with the rubber bulb, which work more like a turkey baster.
You'll also want to address the problem of dehydration. Your dog will be low on fluids if she's not eating and drinking like normal and this will just make her feel even worse (and even less likely to eat) To combat this, you can add plain, unflavored Pedialyte to her water (50-50 mix). This will help replenish electrolytes and hydrate her. When you visit the vet, they can also give her subcutaneous fluids.
I hope your girl is feeling better soon. Don't hesitate to let me know if you have any additional questions!
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