What is the choice of oestrogen only preparations?

What is the choice of oestrogen only preparations?

Oestrogens may be natural or synthetic although both may be manufactured.

When natural oestrogens are taken, the oestrogens in the blood are the same as would be released by the ovaries. Hormone replacement uses natural oestrogens.

After synthetic oestrogen administration, oestrogens structurally different from those released by the ovaries appear in the blood. Ethinyl oestradiol and mestranol are synthetic oestrogens used in combined oral contraceptive pills.

There are several oestrogen only HRT preparations. The oestrogen can be administered orally (tablets –Table 28.2), transdermally (patches –Table 28.3 and Table 28.4 or gels), subcutaneously as implants (Figure 28.1), as a nasal spray (Aerodiol – estradiol hemihydrate - Servier) or by a vaginal ring (Menoring – estradiol acetate – Galen Ltd). The nasal spray and vaginal ring methods have been introduced in 2001.

Table: 28. 2

Doctors tend to have their personal preference for first choice recommendation. As with the combined oral contraceptive pill, the acceptability and side effects for each preparation vary between patients. If you have had a recommendation from a friend or relative it would seem sensible for you to try it.

Premarin is derived from pregnant mares urine. It has been popular for manyyears and much of the research on HRT relates to this product. The pharmaceutical company producing Premarin has documented evidence from veterinary surgeons that there is no cruelty to the animals involved.

Women who have been deprived of oestrogen for more than a few months seem to be prone to side effects and in particular to mastalgia (breast discomfort). It is often wise, particularly if there is a history of mastalgia, to begin with a low dose preparation; the tablets can be taken every few days and gradually increased to the daily regimen.

Oestrogen tablets are broken down in the small bowel where the oestrogen is absorbed. The blood circulating through the bowel then passes to the liver where much is broken down before it has a chance to reach the rest of the body. Sometimes side effects associated with oestrogen tablets may be avoided by using skin patches or by introducing the oestradiol as an implant under the skin. Blood from the skin passes to all parts of the body and not specifically through the liver on its first-pass. Several companies produce patches of different strengths designed to release between 25 and 100 ug (micrograms)/24 hours. Most must be changed twice each week (Table 28.3).

Table 28. 3 Oestradiol skin patches.

Some patches are designed to be changed at weekly intervals:

Table 28. 4 

Some women find that their patches stay in place whilst bathing but most prefer to take the patch off and replace it afterwards. Allergic reactions resulting in irritation and redness can be a problem although the more recent patches seem less likely to cause this.

There are two oestrogen gels (Oestrogel: Hoechst and Sandrena: Organon) for application to the skin. Between two and four measures of Oestrogel are rubbed gently into the upper arms, shoulders or thighs daily usually after bathing. Sandrena comes in 0.5 and 1mg sachets, and the gel is similarly applied each day.

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