Increased levels of free 5-HT have been shown to be present in the plasma o
f symptomatic asthmatic patients compared with levels in asymptomatic patie
nts. In addition, free 5-HT has been shown to correlate positively with cli
nical status and negatively with pulmonary function. These findings suggest
that 5-HT might play a role in the pathophysiology of acute asthma. Accord
ingly, modifiers of the 5-HT transmitter system such as compounds that affe
ct the 5-HT transporter, prejunctional 5-HT receptors or postsynaptic 5-HT
receptors might represent a novel treatment of asthma.