Ronygest 200 and Endogest SR 200 both contain progesterone and are used for similar purposes in pregnancy, but they may differ in how they are absorbed, so they are not always directly interchangeable without medical advice. If you are feeling uncomfortable (such as nausea, dizziness, or other side effects), do not stop or switch on your own; instead, discuss this with your doctor, who can adjust the dose, change the form, or prescribe a better-tolerated alternative based on your condition. Proper progesterone support is important, so any change should be guided by your doctor to ensure safety for you and your baby.