A CYCLOPROPANE COMPOUND REPRESENTED BY THE FOLLOWING FORMULA (A) OR A PHARMACEUTICALLY ACCEPTABLE SALT THEREOF HAS OREXIN RECEPTOR ANTAGONISM, AND THEREFORE HAS A POTENTIAL OF USEFULNESS FOR THE TREATMENT OF SLEEP DISORDER FOR WHICH OREXIN RECEPTOR ANTAGONISM IS EFFECTIVE, FOR EXAMPLE, INSOMNIA: WHEREIN Q REPRESENTS -CH- OR A NITROGEN ATOM, R1A AND R1B EACH INDEPENDENTLY REPRESENT A C1-6 AIKYL GROUP AND THE LIKE, R1C REPRESENTS A HYDROGEN ATOM AND THE LIKE, R2A, R2B, R2C AND R2D EACH INDEPENDENTLY REPRESENT A HYDROGEN ATOM, A HALOGEN ATOM, A C1-6 ALKYL GROUP AND THE LIKE, R3A, R3B AND R3C EACH INDEPENDENTLY REPRESENT A HYDROGEN ATOM, A HALOGEN ATOM AND THE LIKE, AND R3D REPRESENTS A HYDROGEN ATOM AND THE LIKE. (FIGURE 1)
