A new drug on the internet markets is "Zannie."  The drug is delivered with a tongue-in-cheek claim that it is an aersol "air freshener."  In fact, it is designed for internal use.  Ad link is here.

The active ingredient is phenazepam.  This drug is not a controlled substance-so expect it to show up in the usual head shops and corner stores.   Phenazepam's effect is similar to bezodiazepam, except Pheazepam is about 10X as strong.   A typical dose in is the .2 ng range.  Most user's scales are unable to quantify at this level, so users often just guess on dosage.  Overdose is a big concern with this drug.

The drug has a very long potency, although its hard to determine how long because a major effect of the drug is amnesia.  (Which is why OD is a concern).  One user admits he burned through 200 ng over several days because he continued to use while he was high--but cannot remember much after his second dosing.  He does remember destroying various personal items, including his laptop.  The link to the comment is here.