One hundred thirty healthy women with proven ovulatory cycles were randomized, and 127 were treated with the drospirenone-only pill during two cycles. In treatment Group A (n = 62), 24-h delays in tablet intake were scheduled on days 3, 6, 11 and 22 during Cycle 2 and, in treatment Group B (n = 65) during Cycle 1, respectively. Ovulation was defined as disappearance or persistence of a large follicle and progesterone levels higher than 5 ng/mL for at least 5 consecutive days.
The overall ovulation rate was 0.8%; only one subject in Group A fulfilled the ovulation criteria in Cycle 2. Follicular diameters in the regular-intake and the delayed-intake cycles were similar.
Despite the 4-day hormone-free period and multiple intentional 24-h delays in tablet intake, ovulation inhibition was maintained. This property distinguishes this new-generation oestrogen-free pill from traditional POPs by allowing the same “safety window” or flexibility in intake as combined oral contraceptives without compromising contraceptive reliability.
Delayed or forgotten pill intake is very common. Ovulation inhibition by the new-generation oestrogen-free pill, containing 4-mg drospirenone for 24 days followed by a 4-day treatment-free period, was maintained despite four 24-h delays in tablet intake, so the impact of delayed intake on contraceptive reliability will be low.