The dose is based on the extent of envenomation, weight of the person, and ongoing symptoms. Horse serum is actually a giant pain in the ass to deal with. It'

The dose is based on the extent of envenomation, weight of the person, and ongoing symptoms. Horse serum is actually a giant pain in the ass to deal with. It's a crystalline structure that is really hard to dissolve. And, when it gets dissolved, it tends to foam terribly. It generally takes at least 1/2 an hour of slow mixing to dissolve the crystals and get them to stop foaming. So, to compensate for the difficulty in mixing the horse serum, they don't put as crystallized serum into a vial, and the dose requires multiple vials. The standard adult dose is 4-6 vials depending on the size of the person. Hospitals don't stock too much of the stuff (unless you're in an area where rattlesnake bites are endemic) because of cost and infrequency of use. If you're interested in learning more about it, there's a good article here: http://emedicine.medscape.com/article/771455-overview http://emedicine.medscape.com/article/771455-overview