Contraceptive efficacy and safety of a low-dose oral contraceptive, (0.03 mg ethinyl oestradiol and 2 mg chlormadinone acetate) Belara®, over three medication cycles

Abstract

Objective To describe the modulation of ovarian function during three medication cycles with 0.03 mg ethinyl oestradiol (EE) and 2 mg chlormadinone acetate (CMA), leading to inhibition of conception in healthy women.

Methods Phase II, single-centre, open, non-controlled trial. The main outcome measure was inhibition of ovarian activity, assessed by frequent monitoring of the presence, size and persistence of follicle-like structures using ultrasonography. Secondary parameters included: cervical reaction score (CRS-probability of fertilization), endometrial thickness (probability of nidation), and serum levels of the sex hormones oestradiol, progesterone, luteinizing hormone and follicle stimulating hormone. Safety was primarily assessed by monitoring the occurrence of adverse events.

Results Thirty-three subjects were eligible for the trial and were included in the efficacy assessment (per protocol analysis, PPA). All subjects ovulated during the pretreatment cycle, but none during the three medication cycles. Follicular growth was profoundly suppressed during the medication phase, with residual ovarian activity occurring in only 12/83 (14.5%) treatment cycles. The CRS was negative during each medication cycle and endometrial thickness was suppressed on each medication day, with median values of 4.0–6.0 mm. EE/CMA was well tolerated, with few adverse events reported; most were typically cycle-related and included headache, breast discomfort, nausea and vomiting.

Conclusion During the administration of EE/CMA follicular development, cervical reaction and endometrial thickness are profoundly suppressed, resulting in unfavourable conditions for fertilization, implantation and, thus, pregnancy.

Key words:

• Contraception
• Ovarian activity
• Ethinyl oestradiol/chlormadinone acetate
• Belara®
• Cycle stability
• Efficacy
• Safety