I'm unsure as to whether we can claim credit for coining 'sketchy' in this context, but my extended group of friends have been using the word successfully for several years to describe the cumulative effect of an evenings drug use.

"sorry everyone, I just had a sketchy incident in the toilet"

"pox is looking a little sketchy"

can also be used to describe a very happy inebriated state of being.

"How are you feeling pox?"
"Sketchy!" [grinning]

the word may be subject to the usual manipulation

i.e.
sketched out
sketching around

and also more creative attempts such as 'sketch-tastic'

;)
pox