Compounds of the formula I CHEM wherein n is 1 or 2, R1 represents a hydrogen atom or a C1-C4 alkyl group, R2 represents a hydrogen atom and R3 represents a hydrogen atom or a hydroxy group or R2 and R3 together represent a chemical bond, R4 represents a hydrogen atom, or a phenyl or C1-C4 alkyl group, R5 represents a C1-C4 alkyl group or an allyl group and R6 represents a hydrogen or halogen atom, and the pharmaceutically acceptable salt thereof, are useful for the manufacture of a pharmaceutical composition useful in the treatment of emesis.
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