Be careful, the 4F analogue of this "MBDB N-BZ F", as it's known in Russia or 4F-MDMB-CHMINACA as it could also be called has supposedly killed 25 people and hospitalised a further 700 according to reports from the Russian news site RT.com.
I don't know how accurate these reports are and some of the reports may include problems caused by other cannabinoids too or be exaggerated or falsified to some extent and the report itself has a few flaws, but it's clear that these CHMINACA compounds are highly potent and very dangerous.
MDMB-CHMINACA and MMB-CHMINACA are more potent than PB-22, and PB-22 is active with as little as 0.1-0.2mg to a non-tolerant user. So these things are active at like 50 micrograms, more potent than LSD.
Be fucking careful guys. Don't buy these if you don't have a tolerance and a combination of accurate milligram scales and volumetric measurement. Whatever you do, don't buy a blend someone's made using these as if there's hotspots you could end up as a statistic, in hospital or dead.
While you're not gonna die from smoking too much weed, even THC itself can kill, it's just impossible to smoke that much plant matter (or virtually impossible anyway, I'm sure with a machine pump of some kind someone could figure a way out to do it). Cannabinoids in high doses cause seizures/convulsions and can kill as a result of that, THC and some other cannabinoids are also PAMs (positive allosteric modulators) for the mu-opioid receptors, and so potentiate your natural endorphins (endogenous opioids), and the effects of exogenous opioids. With something like THC at a normal dose this means little other than good pain-killing effects and it's part of where the euphoria comes from. With stronger cannabinoids at high enough doses, enough of this effect will potentiate your endorphins enough to see notable central nervous system depression, meaning your blood pressure will drop quite significantly, your breathing and heart beat will slow down, and you could even die as a result of this.
Strong cannabinoids actually most likely have significant enough of an effect as opioid PAMs that they have comparable opioid effects to a partial agonist opioid like say Buprenorphine, or maybe even a full agonist like Morphine. This adds to the euphoria, pain-killing effects, and overall niceness of the high, but also adds massively to how addictive these compounds are, and how easy it is to overdose.
In addition to this, THC and other cannabinoids partially inhibit the release of GABA. GABA is responsible for regulating various things including your mood (GABA reduces anxiety, so strong cannabinoids can induce large amounts of anxiety) and also GABA has an anti-convulsant effect, so too much inhibition of its release can result in convulsions/seizures, which is the most common cause of death by synthetic cannabinoid.
Be careful with these folks. I'm a big fan of synthetic cannabinoids myself, but unless you're a very heavy smoker of them, you should stick to the safer less potent and easier to dose ones like say JWH-073, AM-694, AM-2201, AKB-48,
Here's a comparison pic of all the CHMINACA products that are available that I'm currently aware of. Be careful with any of these, and whatever you do please DO NOT buy blends that contain these as with cannabinoids so potent if your blend is not completely evenly dosed this can lead to hotspots, aka areas of the material that have a higher concentration of the active cannabinoid - ending up smoking/vaporising a hotspot could lead to not just a terrifying very anxious trip but a trip to the Emergency Room/Accident & Emergency after you convulse and have a seizure.
Hope this helps keep some people safe.
[PS I know other people sorta beat me to a lot of the points in this post but I just wanted to make a full informative post to back up the information, clear up any confusion, and make sure it was all understood]