hmm.... i can imagine this probably will not be very good. there is definately a potential for cns depression to be increased although the adderall may counter this as it is a stim.
if you were to take heroin start really small. honestly really small and make sure to monitor the effects every minute/two minutes or so.
heroin can also have a rather detrimental effect on the mind when mixed with clozapine too. be careful with this one if using these medications non recreationally and as intended to treat problems.