Rationale for new oral contraceptive dosing.

The evolution of both the type and dose of the estrogen and the progestin in oral contraceptives has been complex. Whereas the evolution of the progestin component remains dominated by a concern for the metabolic effects of the 19-nortestosterone derivatives, the evolution of the estrogen component has been more of a concern for safety, or perceived safety. By lowering the estrogen dose, some side effects, such as breast tenderness, bloating and nausea, have decreased. At the same time, others, such as breakthrough bleeding and spotting (BTB/BTS), have increased. Indeed, BTB and BTS are the chief reason why women discontinue OCs as well as the primary reason clinicians change the dose or brand of an OC. During the past few years numerous studies have shown inferior cycle control with 20-microgram ethinyl estradiol (EE) OC formulations compared to slightly higher dose OCs. Recently marketed OCs containing 25-30 micrograms of EE have addressed this issue. The 25-microgram EE OCs combined with desogestrel have cycle control equal to a 35-microgram EE OC, whereas the 25-microgram OC combined with norgestimate has shown superior cycle control compared to a 20-microgram EE OC. The 30-microgram EE OC combined with drospirenone in a non-comparative trial is also associated with low rates of BTB/BTS. Our current goal, now that safety issues have been put to rest, is that of identifying formulations that will enhance adherence and increase successful use of OCs.