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At the heart of general practice since 1960

New developments in hormonal contraception

Dr Tamsin Groom and

Dr Kay McAllister review the strengths and weaknesses of new contraceptives

In any 24-hour period there are 114 million acts of coitus worldwide, resulting in 910,000 conceptions and 330,000 sexually transmitted infections. At present in the UK the over-40s undergo the same percentage of terminations as the under-20s.

In the UK we can offer a growing choice of contraception to our patients. The last few years have seen exciting developments in the field of women's health.

Intrauterine system

The Mirena IUS has revolutionised gynaecological practice in the last five years. It consists of a plastic coil with a reservoir releasing levonorgestrel. This results in the progressive atrophy of the endometrium, and to some extent the myometrium below it, leading to a marked decrease in menstrual loss (amenorrhoea in 20-30 per cent of women at year one).

Mirena also modifies ovarian function, with approximately one-third of cycles becoming anovulatory after 12 months. Levonorgestrel increases cervical mucus hostility and has a possible effect on sperm migration in the genital tract, further increasing its contraceptive effect. The Pearl Index – the number of failures per 100 women years of use – for Mirena is 0.02.

Mirena is suitable for almost all women wishing to have effective long-term contraception and particularly useful for those considering sterilisation or those with menorrhagia. Many women complain of increasingly heavy menstrual loss following sterilisation and this usually coincides with the cessation of hormonal forms of contraception; this is an important point to stress when counselling a woman about sterilisation.

As the progesterone is released into the uterine cavity (20µg of levonogestrel in 24 hours), the systemic dose is far lower than any other progesterone preparation, and as a result hormonal side-effects are lower; they also decrease with time. The most common side-effect is menstrual irregularity – usually prolonged spotting. Cyclical progesterone for the first two to three months following insertion may help.

Implanon

This is a small, non-biodegradable implant containing 68mg of etonogestrel. Each comes individually packed in a sterile inserter. Implanon provides the most effective form of contraception available. In studies of more than 70,000 cycles there were no failures, giving a Pearl Index of zero.

Implanon is effective for up to three years and again may be useful for women considering sterilisation, those wishing to leave an interval between children, those who have hectic lifestyles and those who have had problems – such as forgetfulness – with other contraceptive methods.

Etonogestrel is a metabolite of desogestrel (found in Cerazette, Marvelon, Mercilon). Peak hormone levels are reached in four days following insertion and are less than one-sixth of the peak hormone levels from a single combined oral contraceptive pill (COC).

Like all progestogen-containing contraceptives there are possible side-effects. There is a high possibility of irregular bleeding, with one in six women having an intolerable bleeding pattern, one in five being amenorrhoeic and one in two having very light irregular bleeding. The bleeding pattern will remain the same after three to four months, so it is important to counsel women accordingly.

Weight gain associated with Implanon is minimal, and over two years is similar to that gained by women using a copper coil. Headaches, mood swings, decreased libido, bloating and nausea have all been reported in a minority of women.

It is worth considering a trial with Cerazette prior to fitting Implanon in women who have noted side-effects with other hormonal forms of contraception. Insertion and removal are straightforward and there is rarely any need for pelvic examination. Fertility returns rapidly on removal.

In men, studies are ongoing on the use of Implanon in addition to testosterone patches, but these remain available only within trials.

Cerazette

This progesterone only pill (POP) contains 75µg of desogestrel. In clinical trials it was found to inhibit ovulation in 97 per cent of cycles, so it should in theory be more effective than other progesterone-only pills.

But in a trial comparing Cerazette with a levonogestrel POP the Pearl Indices were not significantly different. The trial was not powered to compare efficacy, although when breast-feeding women were excluded a significant difference was noted (0.17 for desogestrel and 1.41 for levonorgestrel).

It therefore seems likely Cerazette is more effective than other POPs and our unit recommends it as the first-line choice for women under 35 who choose the POP as their contraceptive method.

Cerazette's primary mode of action is by inhibiting ovulation, so if a pill is late (more than three hours) or missed additional contraception should be used for a further seven days. Similarly, if not starting Cerazette in the first five days of a cycle, condoms should be used for seven days.

As with all progesterone-only preparations, irregular bleeding is a common side-effect and patients should be counselled accordingly. After four months 50 per cent of Cerazette users had infrequent bleeding or amenorrhoea as compared with 10 per cent of women using a levonorgestrel POP1,2.

Yasmin

Yasmin is a combined oral contraceptive pill containing 30µg of ethinylestradiol and 3mg drospirenone. Drospirenone is an analogue of spironolactone, with anti-mineralocorticoid and anti-androgenic activity. Its benefits are therefore against acne and water retention and it may be particularly useful in individually selected patients.

In high-risk women its use may result in hyperkalaemia and should therefore be avoided in women with renal, hepatic or adrenal disease. However, the antimineralocorticoid effects are similar to natural progesterone with a natriuretic effect similar to a mild sodium-reduced diet.

Women using NSAIDs, spironolactone diuretics, ACE inhibitors, Angiotensin-II-receptor agonists and heparin should not use pills containing drospirenone.

As yet there is insufficient evidence on thrombotic risk. A Swedish study reports a thrombotic risk of 4.6 per 10,000 users per year – more than for second-generation pills3. But the differences were not statistically significant.

Evra

This is another recent addition to our armoury, a 4.5 x 4.5cm transdermal patch releasing 20µg of ethinylestradiol plus 150µg norelgestromin (the active metabolite of norgestimate, the progestogen in Cilest) every 24 hours. Peak levels are reached at 24 hours and plateau at 48, remaining constant for a further seven days. This allows a two-day leeway period if the patch is not changed on time. The company will send text-message prompts to Evra users who register on its website.

Some 80 per cent of the total hormone content remains in the patch after seven days, which has ecological implications. Used patches should be returned to the pharmacy or medical centre for incineration.

The patch has been marketed as a once-weekly method of contraception, with the implication of improved compliance. In trials 88 per cent of cycles were perfect as opposed to 78 per cent of cycles in women using the COC.

The reliability of these findings has been questioned, as have the studies comparing efficacy of the COC and Evra, because numbers were insufficient and there was no statistical difference between the two user groups.

Enzyme-inducing drugs affect the metabolism of Evra; barrier methods should be used in addition to, and for 28 days after stopping, the medication.

When using antibiotics, additional barrier protection should also be used, with the exception of tetracycline, which does not seem to reduce the serum concentrations of either norelgestromin or ethinylestradiol.

Side-effects are similar to those of the COC, except that dysmenorrhoea, increased breast discomfort and breakthrough bleeding in early cycles are more commonly reported.

Evra may be useful for some groups of women, particularly those with malabsorption syndromes and inflammatory bowel disease.

Emergency contraception

Levonelle has now replaced the Yuzpe combined oestrogen and progesterone method of postcoital contraception. The packaging has changed and it is now available as a two-tablet, two-dose pack.

It has also been recognised as being as effective when taken as a stat dose of 1.5mg levonorgestrel, therefore further enhancing compliance. It should be taken within 72 hours of intercourse but will have some effect up to 120 hours.

Overall, progesterone-only emergency contraception will prevent 86 per cent of pregnancies (95 per cent if taken within 24 hours), which sounds better when expressed as an overall actual pregnancy rate of under 3 per cent.

The mode of action is not fully understood. When given before the LH surge it inhibits ovulation in 80 per cent, while in the remaining 20 per cent the luteal phase is shortened and progesterone is low. At or after ovulation no impairment of corpus luteal function has been noted.

The copper IUCD remains the most effective form of postcoital contraception, with failure rates of 0.1 per cent and the option to insert up to five days after the estimated date of ovulation. Although it is widely used as emergency contraception and endorsed by responsible professional bodies, such as the Faculty of Family Planning and Reproductive Healthcare, using a copper IUCD in this way is actually unlicensed. It is worth considering the use of prophylactic antibiotics at the time of insertion.

Further information

More details of contraceptive methods are available at

www.fpa.org.uk

References

1 Faculty of Family Planning and Reproductive Health Care, Clinical Effectiveness Unit. Desogestrel-only pill (Cerazette). Journal of Family Planning and Reproductive Health Care 2003 29(3):162-4.

2 Collaborative Study Group on the Desogestrel-containing progestogen-only Pill. A double-blind study comparing the contraceptive efficacy, acceptability and safety of two progestogen-only pills containing desogestrel 75mcg/day or levonorgestrel 30mcg/day. Eur J Contracept Reproduct Health Care 1998; 3(4):169-178.

3 Kieler H et al. Venous thromboembolism and combined oral contraceptives. Reported adverse reactions indicate at least similar risk with the most recent contraceptive pills. Lakartidningen 2003; 100(39):3050-2.

Tamsin Groom is specialist registrar in sexual and reproductive health care and

Kay McAllisteris consultant community gynaecologist at the Sandyford Initiative, an NHS community family planning clinic in Glasgow

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