So what happens if we do inject antivenom (and hopefully save the life of the snake-bite victim in the process)? The list of equations we'll use will be the same one we used initially, with one exception: our concentration of antivenom, CA, at time zero will be 5 x 10-9 M. This is an arbitrary value that we have chosen for CA, based on an extra tidbit of information that we have; namely, that the normal antivenom dose is typically 3.6 x 10-9 M (although it can be as high as 9.1 x 10-9 M). With this in mind, we decided to make the antivenom dose equal to the venom dose.
Please realize that this is an idealized situation, where the amount of venom injected by a hypothetical cobra is known. Such knowledge would be difficult to determine for an actual snake-bite.
Let's take a look at the resulting plot of the fraction of free sites versus time:
It looks like our snake-bite victim will recover just fine.
