Which medication should be readily available to treat uterine tachysystole caused by prostaglandin administration?

The medication that should be readily available to treat uterine tachysystole caused by prostaglandin administration is terbutaline, specifically at the subcutaneous dose of 0.25 mg. Terbutaline is a tocolytic agent that acts by relaxing the smooth muscles of the uterus, thereby reducing the frequency and intensity of uterine contractions.

When administering prostaglandins for cervical ripening or labor induction, there's a risk of stimulating excessive uterine contractions, known as tachysystole. In such cases, it is critical to have a fast-acting and effective medication to halt these contractions. Terbutaline's subcutaneous route provides a quick onset of action, making it suitable for managing acute situations like tachysystole, where rapid intervention is necessary.

While magnesium sulfate is also used in obstetric care, it serves different purposes, such as managing preterm labor and conditions like preeclampsia or eclampsia rather than immediately addressing the urgent need to decrease uterine contractions due to tachysystole. Thus, the administration of terbutaline in the specified dose is the preferred and most effective treatment option in this scenario.