Propylhexedrine is structurally similar to methamphetamine. The only difference in the two compounds is that an alicyclic cyclohexyl group is used in lieu of the aromatic phenyl group of methamphetamine. It is because of this that propylhexedrine is not an amphetamine, nor even a phenethylamine, but instead can be referred to as a cycloalkylamine.
Propylhexedrine, like amphetamine and methamphetamine, is a chiral compound (the α-carbon is chiral, like in its amphetamine cousins). Like other monoamine releasing stimulants with the amphetamine type backbone, the dextrorotatory isomer of propylhexedrine is much more active as a norepinephrine and dopamine releaser in the central nervous system than the levorotatory isomer is. The propylhexedrine contained in Benzedrex inhalers is racemic d,l-propylhexedrine as the freebase. It is likely that pure d-propylhexedrine would have a higher abuse potential and less undesirable side effects than the racemic compound.
Freebase d,l-propylhexedrine is a volatile, oily liquid at room temperature. This is the form present in Benzedrex nasal inhalers; the volatility of the freebase form insures that some propylhexedrine will be inhaled from the device when used as indicated on the label. D,l-propylhexedrine hydrochloride is a white powder if finely ground, or a clear crystalline substance if the crystals grown are larger. The hydrochloride salt can be vaporized much like the hydrochloride salt of methamphetamine can be.
