What is Yutopar?
Ritodrine (discontinued preparation: Yutopar) is a tocolytic drug, used to stop premature labor. This drug has been removed from the US market, according to FDA Orange Book. It was available in oral tablets or as an injection and was typically used as the hydrochloride salt, ritodrine hydrochloride.
Ritodrine is a beta-2 adrenergic receptor agonist - a class of medication used for smooth muscle relaxation (other similar drugs are used in asthma or other pulmonary diseases such as salbutamol). 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.