There are many manufacturers and brands, but the main thing you need to know is that there are three types of them:
– Monophasic 21-day tablets are the most used type. These tablets are taken daily for twenty-one day, and then an interval of a week (7 days) is made. The example is Yasmin by Bayer.
– Pills with three phases. The packs of such medicines have two or three partitions of different colored pills. They are separated into sections because each of them has a different amount of hormone per pill. They are also taken for twenty-one days with the following break of seven days but these phase pills must be taken in the predetermined order which is defined by the section color, otherwise, the effect is not achieved.
– Daily pills are used for 28 days without interruptions. They actually also contain 21 active pills but also 7 dummy pills so that you can go on using the tablets and don’t have to remember about the breaks between the packages. Though, the use of these formulations also requires a strict observing of the tablets order.The pills are usually started to be taken on any day but there are some exceptions. Read the package insert guidelines to be certain that you use the tablets correctly.
Or better consult your gynecologist.
Besides these differences, the tablets can also be based on different combinations of hormones. It is preferable so that your gynecologist chose the optimal combination for you based on your tolerance of the tablets.