Progesterone-only pills appeal to women for various reasons

Clinical Update – Contraception: Previous progesterone-only pills did not regularly prevent ovulation, and there was a higher failure rate with them, according to Dr Caitriona Henchion, Medical Director of the Irish Family Planning Association.

The previous pills acted on local mechanisms. Cervical mucus was thickened. This made it difficult for sperm to penetrate. The lining of the womb was changed, hindering implantation. Those changes, however, are temporary. The ovaries could be producing eggs, and if a three-hour window for taking the pill is missed, a pregnancy might occur.
Pills that do not contain oestrogen are considered more suitable for women over 35 years with migraine – and particularly for those women who have focal migraine with visual changes. It may be wise for women who have had previous clotting problems to avoid taking oestrogen.
Oestrogen can slightly increase the risk of breast cancer but the absolute risk is small.
Progesterone-only pills appeal to a number of women for these reasons. A number of new progesterone-only treatments have become available recently.
With the older Noriday minipill, a woman could be late by up to three hours in taking a pill. If women were more than three hours late, that would be considered a ‘missed pill’, meaning a woman would have to wait seven days before she is protected and covered by contraception again.
Cerezette is a new product to the market that prevents ovulation as much as the combined pills (at a rate of around 98 per cent). This action makes a 12-hour window for taking this pill possible.
Cerezette’s 12-hour window is the same as that of regular combined oestrogen/progesterone pills.
The progesterone-only pills are all 28-day packs, and this improves compliance. There have been two new combined pills recently. Both have 28-day formulations.
Yaz is a low dose treatment, which has 24 active pills and four daily placebo pills. The treatment also has a shortened ‘break’, which reduces the rate of failures as well.
Side effects may also be reduced. With previous con-traceptives, some women found that towards the end of their pill-free week, they got headaches or pre-menstrual symptoms. “The shorter break with Yaz means this is much less likely to happen,” Dr Henchion said.
Another new treatment, Qlaira, offers good cycle control and reliable contraceptive effects. This treatment contains a natural oestrogen. There are two placebo pills at the end, so a break between packs is not needed.
The oestrogen in all of the pills up to now has been ethinyl estradiol (the closest it had been possible to get to natural estradiol).
In September, Qlaira was licensed. In Qlaira, the ethinyl part has been removed, so the estradiol should be the same as the estradiol valerate in the woman’s own system. Theoretically, this should be better than a synthetic hormone.