Tocolytics are generally administered between 24 and 34 weeks of gestation in cases of preterm labor with cervical changes. They are not recommended for use before 24 weeks or after 34 weeks due to the risk-benefit ratio. Additionally, these medications are contraindicated in situations where prolonging the pregnancy would pose a greater risk to either the mother or the fetus, such as in cases of severe preeclampsia or fetal distress.