the present invention relates to a method for correlating single nucleotide polymorphisms in the preprotachykinin gene with the efficacy and compatibility of a pharmaceutically active compound administered to a human being . the invention further relates to a method for determining the efficacy and compatibility of a pharmaceutically active compound administered to a human being which method comprises determining at least one single nucleotide polymorphism in the nkna gene . said methods are based on determining specific single nucleotide polymorphisms in the nkna gene and determining the efficacy and compatibility of a pharmaceutically active compound in the human by reference to polymorphism in nkna . the invention further relates to isolated nucleic acids comprising within their sequence the polymorphisms as defined herein , to nucleic acid primers and oligonucleotide probes capable of hybridizing to such nucleic acids and to a diagnostic kit comprising one or more of such primers and probes for detecting a polymorphism in the nkna gene , to a pharmaceutical pack comprising nk - 1 receptor antagonists and instructions for administration of the drug to human beings tested for the polymorphisms as well as to a computer readable medium with the stored sequence information for the polymorphisms in the nkna gene .