[wavefunction]

You'd probably have to insufflate (snort) it. That's the recreational method for most users, at least.

[1024core]

Can't you just take a pill?

[joeyo]

Many drugs undergo first-pass metabolism by the liver and their metabolites are much less active or much more non-specific. I don't know if that is the case for ketamine, but I suspect that it must be.