It's a serious medicine, so only take it if prescribed. Focus on gentle breathing exercises instead of heavy physical activity if you are having any tightness.
Terbutaline is sometimes given to stop preterm labor, which is very common with twins. But please do not take it unless your doctor has specifically prescribed it for you!
Terbutaline is a prescription medication used under strict medical supervision, usually for asthma or to delay preterm labor. Please consult your obstetrician directly before taking it.