Norfenfluramine

Norfenfluramine (3-Trifluoromethylamphetamine) is a psychoactive drug which functions as a serotonin releasing agent and potent 5HT2B receptor agonist. The action of norfenfluramine on 5HT2B receptors on heart valves leads to a characteristic pattern of heart failure following proliferation of cardiac fibroblasts on the tricuspid valve, known as cardiac fibrosis. This side effect led to the withdrawal of fenfluramine as an anorectic drug worldwide, and to the withdrawal of benfluorex as an alleged antidiabetic drug in Europe, as both fenfluramine and benfluorex form norfenfluramine as a metabolite.

Norfenfluramine has also been shown to be vasoactive in its own right, causing pulmonary hypertension.