The distinctive valvular abnormality seen with fenfluramine is a thickening of the leaflet and chordae tendineae. Roth suggested a mechanism by which fenfluramine damaged the valves. Heart valves also have serotonin receptors, which regulate their growth. He reported that fenfluramine and its active metabolite norfenfluramine stimulated the serotonin receptors 5-hydroxytryptamine (5-HT). In particular norfenfluramine is a potent agonist of 5-HT2B receptors. These receptors are plentiful in human cardiac valves and appear to be essential for normal cardiac development. Roth suggested that the mechanism by which fenfluramine causes damage is through inappropriately stimulating the valve cells to divide. This valve damage is found in other drugs that act on 5-HT2B receptors.
Valvular regurgitation and surgery associated with fenfluramine use: an analysis of 5743 individuals.(Research article)(Report)
Nov 06, 2008; Authors: Charles F Dahl [1,2]; Marvin R Allen [1,2]; Paul M Urie ; Paul N Hopkins (corresponding author)  Background An...