Sopromidine is a neuroprotective drug. Sopromidine is a potent and stereoselective isomer of the achiral H2-agonist impromidine. The chiral impromidine isomer sopromidine is of special interest as the (R)-configurated compound behaves as gpH2R agonist, whereas the (S)-configurated counterpart is devoid of agonist activity. Both Sopromidine and its S enantiomer acted as antagonists of histamine at H3-autoreceptors with similar potencies (Ki = 5.6 X 10(-8) M and 4.5 X 10(-8) M), whereas Sopromidine acted as an H2-receptor agonist and the S-enantiomer as an H2-receptor antagonist.