Effect of four combined oral contraceptives on blood pressure in the pill-free interval

To evaluate blood pressure changes in the pill-free interval and from baseline among women taking four different low-dose monophasic oral contraceptives.

131 women were randomized to four different oral contraceptives. Pressures were obtained at baseline, at the end of treatment cycles and at the end of the 7 pill-free days, during 6 months of treatment. Pressures were obtained at 4 and 8 weeks after discontinuation. Group 1 received norethisterone acetate 1000 micrograms, group 2 received levonorgestrel 150 micrograms, group 3 received desogestrel 150 micrograms, and group 4 received gestodene 75 micrograms, all combined with ethinyloestradiol 30 micrograms.

All four groups showed an increase in pressure during treatment, with return to baseline levels four weeks after treatment. At the end of the pill-free interval, the readings did not differ significantly from on treatment except for women in Group 4, who experienced an increase in diastolic pressure.

Use of the four oral contraceptives was associated with a small increase in systolic and diastolic pressure. Whatever mechanism causes the increase is not entirely reversible by 7 days without treatment.