Astemizole is a potent antihistamine (H1-receptor antagonist, IC50 = 4 nM) that displays selectivity over dopamine, 5-HT, and muscarinic acetylcholine receptors. This compound has shown potent hERG K+ channel blocking activity (IC50 = 0.9 nM), antimalarial activity in multidrug resistant strains in vitro (IC50 = 227 – 734 nM), and has been used as a chaperone to correct folding defects and restore protein function for some mutated forms of hERG channels.