Don't confuse clozapine with clonidine! Clozapine is an antipsychotic (note both cloZapine and schiZophrenia have a Z). Clonidine is an antihypertensive.
A patient is POSITIVE for orthostatic hypotension if: The SBP decreases more than 20mmHg when changing position AND/OR the DBP decreases more than 10mmHg