Notes: Ritodrine is an agonist of β2-adrenergic receptors (β2-ARs).{47089} It induces relaxation of isolated pig detrusor muscle when used at concentrations ranging from 0.001 to 1 μM. Ritodrine (30 μg/ml) reduces electrically-induced isometric tension in myometrial strips isolated from rabbits on day 25 of pregnancy.{47090} It also suppresses spontaneous motility of and increases concentration of cyclic AMP (cAMP) in isolated pregnant rat uterus.{47091} Formulations containing ritodrine were previously used to stop premature labor.