<prompt> Ritodrine is a:-b 2 agonistb antagonista agonista 1 antagonist  <response>: Selective b2 stimulants : salbutamol, terbutaline, salmeterol, formoterol and ritodrine b2 agonists can be used for preterm labour as they cause uterine relaxation. b2 Stimulators Used in preterm labour : RITODRINE ISOXSUPRINE 