What is used to make medicines for snake bites?

In India, out of so many species of snakes, only four of them are poisonous. But the snake bites caused by them can be life-threatening. Interestingly, the medicine for such injury is prepared using the snake's poison itself. That is why doctors while treating victims of snake bites want to know which particular snake attacked her so the treatment becomes easier. And the medicines are readily available in all the government hospitals.