I started loving 3-FPM approximately 5 minutes after insufflating it for the first time. The euphoric rush lasting half an hour that slowly fades into a very functional stimulation was exactly what I was searching for in a stimulant. It allowed me to study 8+ hours per day, several times a week.
My usual protocol was putting approximately 100mg in front of me and insufflating about a fourth (25mg) every hour and a half to two hours. I did this every day except one for 4 days in a row. I was not strictly speaking abusing it, although I was certainly taking too much at a time.
On the second day, symptoms of cardiac arrhythmia started to appear, which pushed me to start researching reports of various cardiac issues arising from 3-FPM and from its older relative phenmetrazine. It turns out phenmetrazine is well known for its tendency to cause vasculitis, and 3-FPM has been reported by some users to increase blood pressure way more than most other functional stimulants.
The frequency of cardiac arrhythmia is now starting to reduce, 3 days after my last dose. I did feel some mild burn, pain and pressure in my chest approximately one to two and a half hours per day for the last two days, though in a much less noticeable way today compared to yesterday.
3-FPM seems to be cardiotoxic for some people. I would advise everyone to be careful with this substance, particularly regarding cardiovascular health.