Ephedrine and pseudoephedrine have the same molecular formula (C10H15NO) and the bonding sequences, but differ in their three dimensional spatial arrangements, making them stereoisomers. At the molecular level, ephedrine has two chiral centers, giving rise to the four stereoisomers pictured below. The ability of the enantiomers to rotate plane-polarized light differs for each conformation, noted by the (+) clockwise rotation and (-) counterclockwise rotation in the name.Each enantiomer gives rise to slightly different pharmacological potency and biological effects. Ephedrine is commonly used as a bronchodilator, nasal decongestant and a central nervous system stimulant. On a similar note, pseudoephedrine is used to relieve symptoms of congestion of the nasal, sinus, and eustachian tubes caused by the common cold, hay fever, or other respiratory issues as well as allergic rhinitis, croup, sinusitis, and acute otitis media (ear infection). Since both drugs stimulate the nervous system, side effects present when the drugs are consumed in high doses include sweating, convulsions, hallucinations, irregular heartbeat and shortness of breath.Ephedrine is known for its use in the compounding of the drug methamphetamine, because it is a substituted amphetamine and structural analogue differing only in the presence of a hydroxy group.