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Oral Contraceptives

  Oral Contraceptive


Contraception allows family planning and gives women the option to choose when to become pregnant. There are different contraceptive methods available which include combined oral contraceptives, progestogen-only pill, contraceptive implants/injections, contraceptive patches, intrauterine device, sterilization, condoms, diaphragms and caps, etc. The choice of contraceptive methods depends upon factors such as medical conditions, personal preference and the most suitable means for ensuring compliance for individuals. It is important to note that most contraceptive methods do not provide protection against sexually transmitted diseases (STDs) including Acquired Immunodeficiency Syndrome (AIDS). Thus, additional protection such as condoms should always be used to protect against STDs.


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Types of Oral Contraceptive

Oral contraceptive pills, when taken consistently and correctly, are highly reliable (over 99% effective) and reversible. They contain hormones and would prevent pregnancy by one or more of the following mechanisms:

  1. Preventing the ovaries from releasing egg each month;
  2. Suppressing development of uterine lining in order to prevent implantation of egg to uterine lining; and
  3. Thickening cervical mucus to block sperms and egg from meeting.
  Types of Oral Contraceptive

According to their composition, oral contraceptive pills can be categorized into 2 types:

  1. Combined oral contraceptive pills;
  2. Progestogen-only pills.
Although many of the oral contraceptive pills can be purchased over-the-counter, some of them are prescription only medicines for the treatment of acne. The use of contraceptive pills should be under the advice of a doctor and periodic review (no longer than yearly) should be performed by health-care professional to assess the suitability of continued use.

Combined Oral Contraceptive (COC) pills

COC pills are usually referred to as ‘the pill’ and contain two hormones, namely an oestrogen and a progestogen. The oestrogen and progestogen inhibit ovaries from releasing the egg. While the pill is used to prevent pregnancy, it may also be used in the treatment of menstrual disorders such as period pain and endometriosis. Pills containing non-androgenic progestogens (e.g. cyproterone) are often used in the treatment of acne in women who also require contraception.

  Combined Oral Contraceptive pills

COC pills are available in monophasic and multiphasic preparations. Monophasic preparations contain a fixed dose combination of both oestrogenic and progestogenic contents whereas the progestogen and/or oestrogen used in multiphasic preparations vary throughout the cycle mimicking the pattern of natural hormonal secretion in the body. The most commonly used oestrogen in COC pills is ethinyloestradiol. Progestogens that are commonly used in the pill include levonorgestrel, desogestrel, gestodene, drospirenone, dienogest, etc.

The COC pills are usually taken for 21 days with 7 tablet-free days before starting the next pack. Some preparations may include 7 tablets containing no active ingredients so that users do not have to count the number of tablet-free days.

Progestogen-only Pills

Progestogen-only pills (POPs) contain only one hormone, synthetic progestogen, and are known as the minipill. All POPs works by thickening the cervical mucus making sperm transportation difficult and by keeping the lining of the uterus thin thus leading to unfavourable environment for implantation of the fertilized egg. In addition, POPs inhibit the ovaries in releasing the egg but this effect can be variable. Currently, desogestrel-containing minipill is the only POP available in Hong Kong. Unlike the COC pills, the minipill is taken continuously without any break. It can be started on any day during the menstrual cycle provided that the woman is not pregnant, and it should be taken at the same time each day.

The desogestrel-containing POPs are highly reliable (over 99% effective) if taken consistently and correctly. It is often taken by women whom are unsuitable to take oestrogen, including breastfeeding women, older women, heavy smokers, and those with hypertension, valvular heart disease and diabetes mellitus.


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Common Side Effects and Precautions

Types of Oral Contraceptive Pills
Common side effects
1. Combined Oral Contraceptive Pills
  • Nausea, vomiting
  • Breast pain
  • Weight gain
  • Water retention
  • Changes in sex desire
  • Breakthrough bleeding are common in the first 2 to 3 weeks of taking the pill
  • Headache
  • Mood changes
  • Dizziness
  • Depression
  • Hypertension
  • Blood clots in blood vessels supplying the lungs and legs
  • Avoid in patients who are breastfeeding, obese, smokers aged 35 or above
  • Avoid in patients with diabetes, hypertension, congenital or pre-existing heart diseases, family history of venous thromboembolism
  • Contraindicated in patients with cerebrovascular disease, venous thromboembolism, breast cancer, severe hypertension, severe liver diseases, severe migraine, undiagnosed vaginal bleeding
  • Stop taking the pill immediately and use another non-hormonal method of contraception if you have persistent leg, chest or abdominal pain
2. Progestogen-only Pills
  • Irregular menstrual bleeding
  • Nausea, vomiting
  • Breast pain
  • Weight gain
  • Headache
  • Decreased sex desire
  • Depression
  • If the pill is missed for more than 12 hours, additional method of contraception should be used for 7 days or otherwise stated in the product labeling
  • Avoid in patients with history of malabsorption syndrome, functional ovarian cysts, past ectopic pregnancy, and history of breast cancer
  • Contraindicated in patients with undiagnosed vaginal bleeding, severe arterial disease and severe liver disease
  • Higher chance to develop ovarian cysts

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Emergency Contraception

Emergency contraception is a way of preventing pregnancy after unprotected sexual intercourse or due to failure of other contraceptive methods. It is sometimes called the ‘morning after pill’ or the ‘postcoital contraceptive pills’.

Emergency contraceptive pills

The emergency contraceptive pill used in Hong Kong contains progestogen called levonorgestrel. It acts by preventing or delaying the release of eggs from the ovary, thus achieving the contraceptive effect. In Hong Kong, the levonorgestrel-only emergency contraceptive pills are prescription only medicines. Medical advice should be sought to make sure there is no contra-indications before using the pills.

The emergency contraceptive pills must be taken as soon as possible and within a specified time (as stated in each particular product’s label) after unprotected sex to ensure efficacy. Failure rate of emergency pills is about 2 to 3% and they should not be used as a regular method of contraception.


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General advice on taking Oral Contraceptives

  • Choose the most suitable method of contraception only after discussing with your doctor who will advise you based on your personal or family medical history.
  • Take your pills regularly at the same time each day.

  • If you have missed a pill or pills, follow the instructions on the product’s package insert. Emergency contraception may be indicated in some situations.

  • If compliance is a problem, you should discuss with your doctor on other possible methods of contraception.

  • You should see a healthcare professional on the suitability of continued use at least once a year.

  • Do not use emergency contraceptive pills as a regular form of contraception. Emergency contraceptive pills should only be used under medical supervision.


General advice on taking Oral contraceptives


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Communication with your doctor

  • Oral contraceptive pills should be started under medical advice and continued with medical supervision.

  • Inform your doctor of the individual’s drugs and medical history because other drugs may interact with the pill and some diseases may warrant special precautions.

  • Inform your doctor if you wish to breastfeed or are breastfeeding as you may need to choose a particular pill.

  • Read the product information provided with your pill carefully and discuss with your doctor or pharmacist when there are uncertainties.

  • Seek medical advice if you have missed your pill for a time longer than that is allowed on the product’s package insert. You may need to use additional contraceptive method for the rest of your menstrual cycle.

  • If you experience any unexplained pain from leg, chest or abdomen, please seek medical advice immediately.

Communication with your doctor


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Storage of medicines

Oral contraceptive pills should be stored in a cool and dry place. Unless specified on the label, medicines should not be stored in refrigerators. Furthermore, drugs should be kept properly in places unreachable by children to prevent accidental ingestion.



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More information on Oral Contraceptives

Please refer to the following link for more information about oral contraceptives:



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Acknowledgement : The Drug Office would like to thank the Professional Development and Quality Assurance (PD&QA) and the Family Health Service (FHS) for their valuable contribution to the preparation of this article.

Drug Office
Department of Health
Jan 2013