Hi! Logynon is very similar to Trinordiol; both have pills that you take in order for 21 days. Everyone reacts to different pills differently. Hopefully you'll find that Logynon works for you in exactly the same way as Trinordiol, but it might take a month or two to settle down when you change over. If you are changing pill then it's best to start the new pill straight after the old one, rather than have a 7 day break. Hope that helps a little. Your GP or Chemist will be able to advise as well