Contraceptives

About combination contraceptive pills

A commonly used and and effective method of birth control is the combination oral contraceptive (OC) pill. These pills contain a synthetic estrogen, usually ethinylestradiol, and a synthetic progesterone or progestin, of which several are available, combined in the same pill. Ethinylestradiol is used within the dose range that is known to prevent ovulation, but because different progestins have different potencies, their doses vary considerably.

Progestins also have different amounts of androgenic effects, which are actions that mimic the male androgen hormone and cause side effects, like acne and hirsutism (unwanted hair). Newer progestogens have very weak androgenic activity. The first generation progestin norethindone (norethisterone) has low progestational activity (prevents ovulation) and also some androgenic and estrogenic activity. Levonorgestrel and norgestrel are second generation progestins with high progestational and anti-androgen action. Desogestrel and norgestimate are third generation progestins with high progestational activity but minimal androgenic activity. Drospirenone is the newest and fourth generation progestin with a different structure, being derived from spirolactone instead of testosterone. It has high progestational activity but minimal androgenic activity and also has some effect on regulation of water and electrolytes, which helps prevent water retention.

Packs of OC pills contain one month’s supply usually 21 fixed dose combinations of hormone-containing pills, which are all the same, and 7 placebo (non-hormonal) pills, so that one pill is taken each day for a 28 day cycle. Some pills contain different dose combinations of each hormone, such that the dose of hormone increases through the month and the pills must all be taken in the correct order. Contraceptive pills are intended to be taken throughout the menstrual cycle and each monthly cycle should end with a withdrawal bleed and combination.

Combination contraceptive pills for menstrual problems

As a result of taking OC pills combining an estrogen and a progesterone, periods often become more regular, lighter, and less painful; also accompanied by an improvement in pre-menstrual symptoms, like bloating, and fluid retention. Because of this, combination OC pills may be used to treat irregular periods, primary dysmenorrhoea, which is very painful periods without a known cause, often accompanied by very heavy bleeding (menorrhagia), in women who also require contraception.

Combination contraceptive pills for androgen-related problems

Androgens are normally produced in women as well as men but usually only in small amounts. If levels are too high this can cause problems associated with excess androgen production, including hirsutism (unwanted hair), androgenic alopecia (hair loss), acne and seborrhoea (greasy skin from too much sebum). Combination pills containing an estrogen and an anti-androgen are used to combat the symptoms of androgenisation (overproduction of androgen) as well as providing effective contraception. They can also be used to treat polycystic ovary syndrome, which is caused by excess androgen. Cyproterone is the anti-androgen generally used in these combination pills and it also has some progesterone activity.

What is the “morning after pill"?

The “morning-after pill" is a single treatment used as emergency contraception after unprotected sexual intercourse or contraceptive failure, for example a burst condom or missed pill. It is most effective if taken within 24 hours of sexual intercourse but must be taken within 72 hours to be effective in reducing the chances of becoming pregnant. This pill will not have any effect on an existing pregnancy.

How does emergency contraception work?

Levonorgestrel is the same synthetic progestogen that is used in combination contraceptive pills, but is used at a much higher dose for emergency contraception. When taken as a single one-off pill, high-dose levonorgestrel can prevent ovulation or implantation of a fertilised egg, depending at what stage of the menstrual cycle it is taken. If taken within the first two weeks of the cycle it will prevent ovulation before it has taken place, which is when likelihood of fertilisation is the highest. If taken in the second two weeks of the month it helps reduces the chances of implantation by preventing changes in the endometrium that are needed for implantation of the fertilised egg. The “morning-after pill" will not prevent a pregnancy continuing if fertilization and implantation have already taken place.

Progesterone only injection

A progesterone only contraceptive injection contains a high dose of a synthetic progestogen like medroxyprogesterone that is injected once in three months for contraception. These injections inhibit ovulation, growth and thickening of the endometrium and thinning of cervical mucus; they also suppress menstruation if used continually.

Progesterone only injection acts on the endometrium in all its locations to stop it growing and can therefore be used to treat endometriosis, which is growth of endometrial tissue outside the uterus, causing pain and bleeding.

Progesterone only pills

The progesterone only contraceptive pill, also known as the mini pill, is a single hormone pill containing a fixed low-dose of a synthetic progestogen like desogestrel or levonorgestrel. It is taken throughout the menstrual cycle, which includes a normal menstrual bleed.

The mini-pill works as a contraceptive by preventing maturation of the egg, which inhibits ovulation. It also prevents preparation of the endometrium for implantation and thinning of cervical mucus. Taking a mini pill for contraception is particularly useful when breast feeding; also for women who are unable to use estrogen containing contraceptive pills or do not wish to take estrogen because of its associated health risks.