Unisom is safer than opiates for the comedown off this bitch.
I think depending on the formulation of unisom, the drug in it that causes sedation is just an antihistamine, which could be very painful for coming down off amphetamine (or any stimulant), and for a few reasons:
1. The antihistamine would cause vascular constriction, which amphetamine also does - so any negative physical effects caused by vascular constriction such as cold extremities, high blood pressure, muscle weakness, chest pain, etc would be amplified.
2. The antihistamine would further dehydrate you
3. The antihistamines in most (if not all) formulas of unisom are also anticholinergics (as are most antihistamines), which in theory would worsen an amphetamine psychosis. If i remember, amphetamine itself is also an indirect anticholinergic, which is what causes symptoms such as short term memory loss, delusions, bizarre/abnormal thought processes, and dissociation in higher doses.