Adverse drug reactions to herbal and synthetic expectorants.

Our knowledge relating to adverse drug reactions (ADRs) of phytomedicines is highly fragmentary. The aim of this study was to define the prevalence of ADRs following medication with herbal or synthetic expectorants. In a multicentre, comparative post-marketing surveillance study of more than 3000 patients with acute bronchitis, about half were treated with a herbal remedy (SinupretR) and the other half with various other expectorants. In ascending order of incidence, ADRs were noted during mono-medication of SinupretR (0.8%), Ambroxol (1.0%) and acetylcysteine (4.3%). When concomitant drugs were used, this rank order was unchanged but incidence rates were markedly increased (3.4, 6.5 and 8.2%, respectively). The most frequent ADRs were gastrointestinal symptoms. It is concluded that expectorants are associated with ADRs in roughly 1-5% of cases undergoing single drug treatment and in 3-10% when more than one medication is being used. Amongst the expectorants used in this study, the herbal preparation SinupretR is associated with the lowest incidence of ADRs.