The authors of the article which tried to explain the mechanism by which Aminorex and Phentermine cause PAH - by affinity to a certain HT5 serotonine rezeptor which affects the heart - have meanwhile stated that they meanwhile found out Aminorex does not do this, and now no explanation exists how this should happen. (Phentermine though is still a bad one). Aminorex does also not cause PAH in animals and seemingly also not in the USA as the trials there with some 2000 participants which had taken place before those in Europe had found nothing like it. 4-MAR seems to have caused PAH in one group of Americans producing it - if one trusts anecdotal evidence lanced by the DEA.
Also the number of people who got PAH was 2%% (promille, 2 from 1000) whats pretty much the statistically number which was to be expected.
PAH is also cumulative, say when it starts it is self-re-enforcing and nowadays we have medication which stops it when it starts - Viagra and Cialis, the whole group of medication was developed to treat PAH, the other positive effects were just a coiincidence. In short: 5 mg Tadalafil per day keeps PAH away (and provides better circulation to the nether regions as side-effect).
But I do not claim to know for 100% or that I can prove the whole PAH story is bogus. Not yet at least. I would recommend to take Cialis or Viagra in small daily doses when consuming anything from this family and I would include Morpholines like Phenmetrazine just to make sure. I actually would recommend to do this anyways if you are beyond 35 or so.
The reason why 4-MAR vanished is IMHO that it is a VERY long acting drug but not nearly as euphoric and activating as Crystal Meth and Tweakers want to tweak not just be wide awake. 4-MAR simply does not live up to the hype, similar to most RCs which usually pale when compared with plain Amphetamine or 2c-B or MDMA not to talk of LSD.