I've heard of ketamine being used with-meth, and Ketamine, which is much more costly, has been known to be mixed with meth to "stretch" it and increase the profits through the distribution chain.
The two drugs' effects are, from what I understand, quite dissimilar, but in some people, compliment each other.
Remember, I've only had Ketamine in a supervised medical setting, and I've never so much as tried methamphetamine. 1st of all, when I was in the drug scene, methaphetamine (which we called crank or ice) users were the lowest of the low. 2nd of all, ampetamines, or speed of any kind, just do not agree with me, physically or mentally, and I've taken several forms of amphetamines during my early years.
I do not like the high, and i especially do not like the comedown. Knowing that, and knowing that meth is the most potent of all the amphetamines (not counting some of the "research chemicals" (google this for an eye-opener), why would I try it if I hated the milder stuff.