Ritodrine hydrochloride (DU21220 hydrochloride) is a β-2 adrenergic receptor agonist. Target: β-2 Adrenergic Receptor Ritodrine is a tocolytic drug, used to stop premature labor. Ritodrine can significantly prolong a short interval more quickly but with relatively more side effects than magnesium sulphate. Stratified RCTs for different gestational ages and different labour stages should be designed for further study [1]. Ritodrine is a beta-2 adrenergic receptor agonist - a class of medication used for smooth muscle relaxation. Since ritodrine has a bulky N-substituent, it has high β2-selectivity. Also, the 4'-hydroxy on the benzene ring is important for activity as it is needed to form hydrogen bonds. However, the 4'-hydroxy makes it susceptible to metabolism by COMT. Since it is β2-selective it is used for premature labor [2].