Which pill?

Dr David Delvin discusses how to match oral contraceptives to patients

The oral contraceptive (OC) is so popular these days that the average GP now has approximately 100 pill-taking patients on his/her list. Indeed, the very positive report by the RCGP1 released this January which showed that the long-term health risks of the pill are very low, will probably help to make the OC even more widely used.

But choosing a brand of pill is not all that easy, especially as there are now 26 different brands of combined pill and six brands of mini-pill (progestogen-only) on the market. However, I find that by following the decision processes outlined below, it is usually fairly easy to get patients established on pills which will suit them.

Ordinary pill or mini-pill?

The vast majority of our patients need the combined pill, but a minority are better suited to the mini-pill or 'progestogen-only pill' (POP), often mistakenly called the 'progesterone-only pill'. These preparations are the only ones which are suitable for breast-feeding mothers and women who can not take oestrogens. They are also useful for diabetics, older women, heavy smokers, and for anyone who wants to take a break from the combined pill.

It is important to tell the woman about the higher failure rate of mini-pills. Also, bear in mind that some patients are not very good at remembering to take mini-pills at the same time of day, 365 days a year. Currently available POPs are shown in Table 2.

Combined pills

Three brands of combined OC are available in every day (ED) formulations. These products contain seven dummy (placebo) tablets as well as the 21 active ones. They are used by women who prefer to take a tablet every single day of the month.

In practice, while EDs are very popular in some overseas countries, only a minority of British women use them. The three available brands are:

• Microgynon 30 ED
• Femodene ED
• Logynon ED

Dosages

Some doctors prefer to prescribe pills in which the dose varies at different times of the woman's cycle. The idea behind this is to reduce the total dose of hormone administered. Also, it is sometimes claimed that cycle control is better with these multi-phasic pills. However, the International Planned Parenthood Federation (IPPF) has recently said that there is 'no evidence that multi-phasic OCs are more effective or safer.'²

The concept of using a bi-phasic or tri-phasic pill is intellectually attractive, but one has to remember that some patients do get confused between the different-coloured tablets. Available multi-phasic pills are listed in Table 3.

Low, medium or high strength?

Combined pills are classified as low strength, medium strength or high strength, depending on how much oestrogen they contain. Low strength pills have 20 micrograms of oestrogen, medium strength ones have 30 to 40 micrograms, and high strength pills contain 50 micrograms.

Low strength and medium strength pills both give very good results. These days the only two remaining high strength pills (Ovran and Norinyl-1) tend to be used mainly for women who do not get good enough cycle control with lower-dose brands.

Choice of progestogen

All the progestogens used in today's pills are safe and effective for most women. However, because of the somewhat controversial decision taken by the Committee on Safety of Medicines in 1996 to publicise an alleged higher incidence of thrombosis with two progestogens, the current official advice is that combined OCs containing the progestogens gestodene or desogestrel should only be given to women who are intolerant of other brands, and 'who are prepared to accept an increased risk of thromboembolism'. In practice, if any increased risk exists, it must be very small.

Changing brands

If a patient has tried a particular pill for three months or so and still is not happy with it, it is best to change brands empirically and see if another one suits her better. Care is needed here, because unwanted pregnancy can occur as a result of a change of brand. Occasionally, this has resulted in the GP being sued!

Different authorities give slightly different advice about changing OCs. The Family Planning Association says that 'when changing from a higher dose preparation to a lower one, or from a combined pill to a POP (or vice versa), the first pill of the new packet should be taken on the next day immediately after the last active tablet of the old packet'. In contrast, the British National Formulary (BNF) merely recommends that if you are changing the patient to a different progestogen, she should start on the new brand immediately after the last active tablet of the old one.

Worldwide, other authorities give slightly differing instructions. My advice is that if there is the slightest doubt in your mind, suggest to the patient that she takes additional precautions for the first 14 days on the new pill.

Conclusion

Rather than try to learn the characteristics of every single product on the market, it is probably best to get to know several brands of pill well and become practised in matching them to your patients' needs and preferences.

David Delvin is a part-time GP and Family Planning Instructing Doctor who runs a private psycho-sexual/contraceptive practice in London and Cambridge

References
1 Beral V, Hermon C, Kay C, Hannaford P, Darby S, Reeves G. Mortality associated with oral contraceptive use: 25 year follow-up of cohort of 46,000 women from RCGP oral contraceptive study. Br Med J ; 1999; 318: 96-100
2 IPPF International Medical Advisory Panel. IMAP statement on steroidal oral contraception. IPPF Medical Bulletin December 1998; 32(6): 1-6
3 Belfield T. FPA Contraceptive Handbook 2nd Ed. London: Family Planning Association 1997: 49
4 British National Formulary. London: BMA and Royal Pharmaceutical Society September 1998 (36): 353 5 Guillebaud J. The Pill 5th Ed. Oxford: OUP 1997