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JC Dill
JC Dill, AFA Certified Farrier Equine expert
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How much penicillin do I give a 1000 lb horse in a dose?

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My horse slipped on some lava rock & has cuts on 3 legs. The one on the front leg was pretty deep. And took out a piece of skin the size of a golf ball. I cleaned the wounds & bandaged them. I now giving my horse penicillin, and want to know how many days & how much should be given. The horse weighs around 1000 lbs.

Submitted: 8 years ago.
Category: Pet
Expert:  JC Dill replied 8 years ago.

The procaine penicillin G available in feed stores for use in horses typically has 300,000 IU per ml. The standard IM dosage for horses and ponies is 22000 IU per kg. of body weight. Your ~1000 lb horse weighs ~454 kg, so the appropriate doseage is 33 ccs - usually the vets round up to 35ccs or if they think the horse may be a bit more than 1000 lbs then they round up to 40ccs. On the other hand, you can get 3 33cc shots per 100ml bottle. (BTW, ask if your feed store carries 250 ml bottles. Mine does, for less than 2x the cost of the 100ml bottles.) The shots need to be given IM 2x daily, for a minimum of 7 days - 10-14 days is usually recommended. If you discontinue the injections too soon this can result in antibiotic resistant bacteria which is a very serious problem. If the leg is still swollen after 14 days you can keep giving the antibiotics until all signs of swelling and infection are gone. You don't want to give antibiotics unless it's really needed, but when it's needed (as in this case) you don't want to discontinue it too soon.

Please see this link for more information about how to safely give IM injections:

How To Give Your Horse An Intramuscular Injection

You will also want to give some bute to help reduce the pain and swelling. If the horse is very lame or the legs very swollen give 2 grams of bute 2x daily. If there isn't a lot of pain or swelling, then 1 gram 2x daily. After 7 days, you can go to 1 gram 1x daily, and after another 7 days stop the bute if the horse is not serious lame and doens't have much swelling.

The bandages need to be changed daily as long as the wounds are seeping. Once the wounds close up and aren't seeping you can leave the bandage on that leg for 2 days, and if it isn't seeping when you change that bandage you can leave the next one on for 3 days. Be sure the bandages aren't too tight and aren't too loose. Use lots of cotton padding between the bandages and the elastic or vet wrap padding on the outside layer of the bandage.

Your horse needs strict stall rest to help these wounds heal, and also to keep the bandages clean and keep them from slipping with exercise. Hand walk for 15-30 minutes a day for exercise. If your horse has been fed grain, you want to cut back to just enough to feed the bute (if any) and no more - to reduce excess energy when you are keeping the horse pent up in a stall with limited exercise. If you don't normally feed grain, make a mash with hay pellets. Dissolve the bute tablets in water, then add pancake syrup to sweeten and mask the flavor of the bute. Then add to a small amount of hay pellets.

Good luck!

Customer: replied 8 years ago.

Thank you , you have answered almost all of my questions. Can I convert the dosage to ground up tablets. Instead of the shots. If so, I purchased tablets at the feed store. They are 250 mg. So, how many mg or tablets. should I give my horse then?

Expert:  JC Dill replied 8 years ago.
In order to convert the doseage I need to know how many IUs per MG or per tablet. The 250 MG figure is how much "stuff" is in the tablet but not all of that is the penicillin medicine - most of it is the carrier, the chalky stuff that makes the tablet.
Customer: replied 8 years ago.
Reply to JC Dill's Post: Sorry, The only thing on the bottle is 250MG. I bought it at a feed store. It was not given to me from a Vet. It does say that it is potassium penicillin. I probably wasted my money on these tablets, didn't I.
Expert:  JC Dill replied 8 years ago.

There should be more information on the label. Can you give me all of the text on the label, including the manufacture?

Is there some reason you don't want to use injectible penicillin? The link I provided above will help you determine the right places to give the injections.

I went thru this same situation last February/March. My filly sliced her hock on a wire fence. I gave her IM penicillin for about a month until the infection in the wound had cleared up. I just alternated from one buttock to the other - morning shots went on the right side, evening shots went on the left side. She never had any problems with the shots. The important thing is to give the shots on the REAR portion of the buttocks as shown at How To Give Your Horse An Intramuscular Injection

Customer: replied 8 years ago.
My horse is reacting alittle to the shots. The reason that I don't want to give her the shots are is That I just had knee surgery about 3 months ago. If she reacted, I couldn't get out of the way. I could possible re-injure my knee and have to go in for surgery again. Thats the reason that I would rather mix up a paste & give it to my horse.
Expert:  JC Dill replied 8 years ago.

One way to safely give shots is over a door or wall. Have someone hold the horse in the stall with the rump next to the stall door, and you give the shot from over the door. It also helps to give the horse food treats while and after giving the shots - positive reinforcement so that she learns to stand quietly and tolerate this procedure. My mare only reacted to the first few shots. After a few days, I'd put her mash (with the bute in it) in her bucket and then give her the shot without even putting her halter on.

I can lookup more information about the pills if you can give me all the info on the label. If it's a hand written label call the feed store and ask for the label from the box or bottle the pills came in.

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