GIVING INTRAMUSCULAR INJECTIONS The fleshy area of the horse's neck (see photo) is the most commonly used injection site, as it's the safest spot for the person doing the injection. I prepare the site by brushing off loose dirt and hair, washing it with soap and water and wiping it (down to skin level) with alcohol. Hold the needle between your thumb and first finger, touching only the hub (top). [caption id="attachment_376" align="alignnone" width="555"] This needles is properly inserted, straight into the horse’s neck for its full length.[/caption] [caption id="attachment_377" align="alignnone" width="555"] Since necks often become sore after multiple injections, alternate sites are needed. The best bet is the large muscle mass of the upper hind leg.[/caption] Aim for the center of your target area. Quickly and forcefully place the needle deep into the muscle. This should be done in a manner similar to shooting a dart. Slow insertion, or hesitant insertion, causes much more pain. Also, do not slap or punch the horse before inserting the needle. That doesn't numb the area but does upset the horse. Next, securely attach the syringe containing the medication to the hub. Pull the plunger back very gently to see if the syringe fills quickly and easily with blood. If you get blood filling the syringe, remove the needle and use another spot. If you do not get blood, then inject the medication at a slow and steady pace.

Excerpted from, Dr Kellon's Guide to First Aid For Horses 
copyright © 2006 Eleanor Kellon VMD
This excerpt reprinted by permission of Trafalgar Square Books