My experience with slippery elm and my dog. My dog has had very bad acid reflux for years and unfortunately no vet, holistic or traditional has been able to help (they only say take Pepcid - a very bad solution). After a dental procedure in July 2013, we were given antirobe to give to our dog. It's a very potent anti-bacterial drug that is strong enough to penetrate bone. The acid reflux became so severe that our dog would faint and have a seizure from it. Again, no vet, holistic or traditional knew what to do. So, as I always do, I researched and found slippery elm. It was a "miracle" for a month. Then, he started to show signs that again no vet, holistic or traditional (we went to 5 different vets for help) knew what was going on. From Sept. 2013 thru Dec. 2013 there were symptoms which included: extreme hind side pain, wouldn't eat unless it smelled right, excessive thirst (he's got kidney disease so we thought he could be in renal failure), dry eye, etc. We tested for numerous things. I questioned everything (as I usually do). He got sub-cutaneous fluids and homeopathic remedies. It was miserable for him and for us. He would only eat liver. We got a vet nutritionist to help. Finally, after he lost a pound in a matter of weeks and then gained several pounds in two weeks, it dawned on me. It's the slippery elm that stopped the absorption of his hypothyroid medication that caused this. Yes, as I said, the severe reflux improved to just minor episodes for a month but the reflux came back anyway and in addition, he now didn't have enough thyroid medication in his system. I followed the directions of what I found online for the slippery elm (which wasn't adequate - 1 hour before the medication) because as I asked every vet no one had an answer for me except one after the fact (as that one vet mentioned, "The slippery elm should always be given at least 2 hrs before or two hours after any other medication.") Of course, no vet wanted to believe my conclusion until all the symptoms finally went away during the weeks following the end of the slippery elm usage. It took about 12 - 16 weeks following the end of the slippery elm usage for the symptoms to be completely gone and his thyroid to be back to normal. We now have found other alternative health solutions for the acid reflux (still all the vets wanted him to take Pepcid) that appear to be working.
I'm not saying to not use slippery elm. I've heard of it being helpful for very sick animals outside of this forum, too. Just please be careful if your dog/cat is on any medication (although we try very hard to use alternative health solutions, he eats home cooked organic food, thyroid medication is a necessity for our dog). I also do wonder if the slippery elm does not allow for the complete absorption of nutrients when given with food. If it causes lack of absorption of medication, that leads me to believe it could cause lack of absorption of nutrients, too.
Another thought, when a vet says that tests or study's were done on humans so the result might correct not be for dogs/cats, trust your instinct. Who's to say it might not be for them, too. BTW: every single symptom I researched that was about humans applied to my dog and led us to be able to help him. Also, he was never in renal failure (YAY! ), his excessive thirst was due to dry mouth which IS (no vet wanted to believe which caused the wrong homeopathic remedy and was just a waste of time and money) a symptom for hypothyroidism (in humans AND dogs). In addition, I found a study from the NIH that stated that humans who have hypothyroidism can have their sense of taste and smell thrown off because of it. And finally, we couldn't understand why our dog would only eat liver for weeks (which made us a bit nervous). Turns out liver is very good for the thyroid.
Bottom line: listen to your animal and then, yourself! Good luck to everyone.