Trigestril is similar to the pill triphasil
in action and the usage. The pill should be started on the first day of the mensus. The first tablet that should be taken should be from the first red tablet area. The tablets should be taken at roughly the same time daily and should be taken within 24 hours of the previous tablet. After the first tablet, you should continue taking the tablets in the order given by the arrows on the pills cover.
This above website gives a detailed explanaion of all the effects of triphasil pills. I hope this helps you.