HTR2B and pulmonary arterial hypertension: However,the use of these appetite suppressants was associated with cases ofprimary pulmonary arterial hypertension (PAH) and changes at the heartvalves.318 Through receptorome screening,Roth and Setola showed the role of the metabolite formation in theundesirable side effects observed of these drugs.316 The activation of mitogenic 5-HT2B receptorsby norfenfluramine 184 (Scheme 69), a fenfluramine metabolite, revealed thepossible molecular mechanism responsible for the adverse cardiopulmonaryeffects of fenfluramine.