Dr. Kirsty Horsey
Progress Educational Trust
21 April 2006
 [BioNews, London]
British women are being denied newer fertility drugs that help prepare the woman's body for egg stimulation, according to Bill Ledger, Professor of Obstetrics and Gynaecology at the University of Sheffield, The Times newspaper reports. IVF treatment requires a woman's ovaries to be stimulated in order to harvest eggs for external fertilisation. For this to happen the woman's natural menstrual cycle must be temporarily overcome. There are two classes of drugs that allow this to happen, which work to block a hormone called Gonadotrophin-releasing hormone (GnRH).
GnRH agonists are used in the majority of British fertility clinics. These drugs (the IVF 'long protocol') work by mimicking the hormone in the brain and binding to the receptors to block the natural hormone from attaching. These drugs are typically given for 14 to 21 days before the patient's period is due and they initially cause a sharp increase in hormone levels. As the hormone levels drop, menopause-like symptoms can occur including hot flushes, mood swings and insomnia. The alternative, newer treatment, involves using a different class of drugs - GnRH antagonists (the IVF 'short protocol'). These drugs do not bind to the hormone receptors in the brain, instead they bind to the hormone itself, allowing for a rapid decrease in hormone levels without the initial sharp increase. As antagonists reduce hormone levels much more quickly they can be given for a shorter period of time - around six days - meaning that side-effects are rare.
Developed in the 1990s, GnRH antagonists are used in 80 per cent of IVF cycles in Scandinavia. As well as reducing the instance of menopause-like side effects, the IVF short protocol also reportedly reduces the risk of ovarian hyperstimulation. British clinics have been slow to switch to the new drugs as in early trials they were shown to produce an average of 1.0 to 2.3 fewer eggs and 0.2 to 0.5 fewer good quality embryos in each cycle. Pregnancy rates were slightly lower but not statistically significant.
Professor Ledger argues that these studies took place before most doctors had experience of the new drugs and that the reason they are not used in Britain is due to the clinics' fear of falling in the success-rate league tables. The one trial that compares clinics that are experienced in the new regime found no appreciable difference in pregnancy rates between the two methods. 'The uptake of these drugs has been slower because of the conservative nature of IVF in Britain', Professor Ledger said. 'Clinics are terrified of a drop of a few points in their success rates if they switch', he added.
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Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.
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