thank you for your query.
Drotaverin in established labour helps in ripening the cervix
However in your case at 28 weeks, it helps in relieving uterine spasms
Please go ahead in full faith with your doctor's advice.
The medicine is safe to take if you DO NOT want to go into labour.
However if you are having established preterm labour pains, this would not work.
Then you would require intensive tocolytics ( discuss with your doctor ) and steroid
cover to enhance the lung maturity of your baby in case a preterm delivery occurs.