Welcome to HCM
is a stimulant drug and its an amphetamine
. It increases heart rate
and over all cardiac output. So the increase in heart rate in you is due to increase in dose in morning as previously you were taking 20mg extended release which is long acting and now its 25mg, so due to this dose adjustment HR has increased. As immediate release dose has nothing to do much because its short acting only and its decrease just will not affect much.
Hope I solved your query.
Thanks Take care