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Hi. I have a 5 yr. old with a stifle injury. He got jabbed with a slide latch that's on a half gate in his stall and he somehow opened it and did this in his stall in the middle of the night. 
Anyway, he did this last weekend. He got penicillin, Gent. and bute. I was icing for 2 days. 4 days later, after being on nothing since the accident (vet didn't seem to think he should be on anything), it became infected. Well, I had to give 10cc's of Gent. twice a day and 20cc's of Penicillin twice a day, in shot form. I've been doing that since Thurs. eve. and hot packing twice a day. The swelling has gone down and the cut is still seeping. He's still sore and limping on it. 
 The vet wants me to give the rest of the Gent. shots till the bottle is gone (only 10cc's once a day) which may take me till next week. 
My question is, what is a dangerous amount of Gentamicin to be giving? I'm obviously second guessing my vet because I have to keep asking what to do next. 
Thanks!

Deb