Salsa has been on metformin tablets for almost three weeks now and is getting increasingly harder to syringe them into.
The metformin IS helping him with his sore feet and lab tests show insulin dropped into the 30s now on it (his best EVER).
Due to a mouth injury as a yearling - Salsa is always "less than pleasant" to syringe meds/dewormer into.
He'd been sort of ok about the metformin in milk of magnesia until Monday (2 week mark) and then he just quit having it.
He won't eat the metformin 'whole' in feed - been there, done that. 
Hubby went out with me and was like "you have to figure something else out before you get hurt" trying to syringe it in - and he's right - this is getting to a level that has to stop.

Two times now I have ground the human tablets up and put them in some wet feed.  He does it eat this way no problem - but I worry about irritation to his mouth/throat.  I do make sure he has hay after this to eat.

Talked with my compounding pharmacist (who talked to his compounding buddy that does more animal meds) and he is getting an apple flavor powder and is going to give me some as a sample to see if Salsa will eat that.
He said the flavored powder has a ph adjustment in it that should prevent any irritation and he even said if I don't mind grinding the human tablets up - he can sell me the flavored powder and I can mix it in with the ground up tablets and put that in Salsa's feed.  He should have the powder on Tuesday.
If he compounds the metformin into this powder for me - will be about $70 a month vs current $15 or so for the human tablets.

Questions - is the current ground up metformin tablets in some wet feed something I really need to stop asap?  Can I get away with this for a few more days to get the powder and hope he likes the taste?  Maybe I can TRY to syringe in some plain milk of magnesia after he eats the ground tablets in his feed (where I'm not so concerned with getting every drop into him like when I mix it with the metformin)?

What about the pharmacist selling me the ph balanced powder (if prince picky-pants will eat it) and I just add it to the metformin tablets that I grind up? 

I can't get hurt getting metformin into Salsa.  Not an option.
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Tracy and Salsa (1999 model year Paso Fino)
Middle TN USA, September 2019
Case History  https://ecir.groups.io/g/CaseHistory/files/Tracy%20and%20Salsa
Photos https://ecir.groups.io/g/CaseHistory/album?id=95827