Emopamil is a phenylalkylamine calcium antagonist. Emopamil has optically active stereoisomers. Emopamil enhanced the postischemic restoration of high-energy phosphate levels. The racemic mixture and the (-)-enantiomer of emopamil caused similar metabolic changes while (+)-enantiomer of emopamil proved to be ineffective. Emopamil is able to reverse multi-drug resistance in human KB cell lines. No differences in reversing potency were observed between emopamil (R)-isomers, (L)-isomers and the racemic form. There is a pharmacological relationship between sigma1-binding site and the mammalian sterol C8-C7 isomerase which is identical with the emopamil binding protein.