Lacey,
I can speak w/ a little knowledge on this topic. My understanding is if you have drug induced PH, it is actually manifested as PAH. I have idiopathic PAH, which means the origin of why I succumbed to this condition is not known. It could be Drug induced. As AI said the appetite suppressant phentermine which I took many years ago, & I had a drug issue that I successfully worked out many yrs. ago. Also the COPD can cause the PAH. I really feel like if I only had a back ground of drugs w/ no COPD or if I had COPD w/ no drug background than perhaps I could have skated by without acquiring this condition but I got a double whammy w/ both issues. So basically there is no way for me to have escaped it.
Also as AI mentioned that quitting a certain category of drugs will no longer cause PH or PAH. Those are pharmaceutical drugs AI is speaking of. I'm not sure if you are inquiring about all drugs in general or specifically pharmaceutical drugs or the illegal street drugs that AI should have mentioned. The diet pill was legal but the use of Methamphetamine & Cocaine can also cause PAH. Many times you don't acquire this condition until yrs. later after the illegal drugs are no longer an issue. So my belief and experience would say that if you are inquiring about illegal drug use, that no you don't get lucky enough to quit the drug and have PAH quit also. PAH is a condition that is gradually gets worse especially left untreated. But even if I or you or anyone else is currently engaging in illegal drug use and we get PAH it will not resolve & go away when we decide to no longer do drugs. Now don't misinterpret my explanation. If a person decides to use illegal drugs today & says ahh this ain't for me a week later more than likely they will not develop PAH.
Because PAH is so difficult to diagnose, it is actually doing it's thing to the pulmonary artery for a while before symptoms manifest, that by the time it is diagnosed, unless you are so lucky to get diagnosed by PAH expert, by the time it got diagnosed for most of us it was full on & the pulmonary artery has been really affected. Part of that is also that the pulmonary artery has to do it's thing shrinking however it is described, that at a certain point of the pulmonary artery doing it's thing quite a bit before a person even knows what's happening. Someone correct me if I'm wrong. I couldn't be thorough enough about this condition w/ out it turning into a long post. Sorry.

I believe you are totally correct.

Dohickey,
Thank you for your response & support.... I hope you have a good Mon. start to your new week. Hope the entire week is good for you, in whatever way you need it to be!!!!!!!!!!!!