The present invention relates to 1-amidino-3-aryl-2-pyrazoline derivatives of the general formula IThe invention specifically relates to such derivatives which exhibit antagonizing activity towards serotonin 5-HT2B receptors. The present invention also relates to use of said compounds as a medicament and for the treatment of fibrosis, cardiovascular diseases, pain, IBD, and other inflammatory diseases, as well as pharmaceutical compositions comprising one or more of said compounds and methods of treatment.