The dextrorotary (+)- or d- enantiomer is (1S,2S)-pseudoephedrine, whereas the levorotating (−)- or l- form is (1R,2R)-pseudoephedrine.
In the outdated  system (+)-pseudoephedrine is also referred to as pseudoephedrine and (−)-pseudoephedrine as pseudoephedrine (in the Fisher projection then the phenyl ring is drawn at bottom).
Often the  system (with small caps) and the d/l system (with lower-case) are confused. The result is that the dextrorotary d-pseudoephedrine is wrongly named pseudoephedrine and the levorotary l-ephedrine (the diastereomer) wrongly ephedrine.
The IUPAC names of the two enantiomers are (1S,2S)- respectively (1R,2R)-2-methylamino-1-phenylpropan-1-ol. Synonyms for both are psi-ephedrine and threo-ephedrine.
Pseudoephedrine is the International Nonproprietary Name of the (+)-form, when used as pharmaceutical substance.