Dextro-amphetamine sulphate

Recently-ish seitched from 30 mg daily ritalin to 30 mg of this, as elvanse/vyvanse is not abailable in Belgium. It worka great and helps me get stuff done, actually cleaning and doing daily tasks without thinking twice about it. Problem is whenever i take it my heart rate is through the roof. Anyone with knowledge or experience know wether taking multiple smaller doses a day like 3 doses of 10 mg can help mitigate this? My heart rate goes from 70-75 resting to 90 and sometimes 100+ , i also have autism in case that’s relevant. I’m 22 and 102 kg, dosewise it checks out but maybe it’s being released too fast in my system or something. I also am an occasional smoker and do vape which does make it worse, but the 100 bpm reating heart only happens when i’m on my meds. I did take a two week break due to shortages in supply and while i did notice a higher heart rate when i started out it sort of got better after a while, but now i feel my heart racing constantly after leas than a week of getting them back, i also fee quite anxious which is one of the side effects but then again my heart is working overtime and i’m worries.