Usually cycle postponement medications should be taken at least 3 days before expected periods and at a higher dose. In the current situation, you may try primolut N 5 mg three times a day every 8 hrs( time specific - have to be strict with timely intake ) for maximum of 5 days (not guaranteed as you are starting only 2 days prior). 5mg dosage will work only if it is started at least a week before.
Health Tips
Better to avoid if possible
High dose of progesterone , might give you headache,breast tenderness,nausea etc
Next cycle can be irregular.
Not advisable to take if you have migraine or any other medical issues