Oral Contraceptive Pills An Overview


Oral contraceptive drugs, employed primarily for preventing unwanted pregnancies, embody a range of formulations with distinct pharmacological profiles to cater to individual needs. Here’s a comprehensive overview of their pharmacology, types, recent advancements, adverse effects, and contraindications:

oral contraceptive pills
OC Pills

Oral Contraceptive Pills: An Overview

Oral contraceptive pills, often simply referred to as “the pill,” are a type of medication taken daily to prevent pregnancy. They contain synthetic versions of the hormones estrogen and progesterone, which naturally occur in the female body. These hormones regulate a woman’s menstrual cycle and prepare the body for pregnancy. By manipulating these hormones, oral contraceptive pills can effectively prevent ovulation and fertilization.

Classification of Oral Contraceptive Pills

Types of Oral Contraceptive Pills:

  • Combined Estrogen-Progesterone Pills: These encompass synthetic versions of both estrogen and progesterone hormones, inhibiting ovulation, thinning the uterine lining, and thickening the cervical mucus to obstruct sperm from reaching the egg​1, ​​2​.
  • Progesterone-Only Pills: Containing only synthetic progesterone, these primarily work by thickening cervical mucus and thinning the uterine lining to avert sperm entry and implantation, respectively​1​.
  • Continuous or Extended Use Pills: Typically a form of combined pills, they are taken in extended cycles or continuously without breaks​1​.

Mechanism of Action of Oral Contraceptive Pills

Oral contraceptives curtail the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus, subsequently inhibiting the release of pituitary hormones that stimulate ovulation​3​.

Mechanism of Action of COCs

COCs work by suppressing the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland. This prevents ovulation, meaning no egg is released for fertilization. Additionally, COCs thicken the cervical mucus, making it harder for sperm to reach the egg, and thin the lining of the uterus, making it less likely for a fertilized egg to implant and develop.

Mechanism of Action of POPs

POPs primarily work by thickening the cervical mucus, which prevents sperm from reaching the egg. They also thin the lining of the uterus, making it less hospitable for a fertilized egg. Some POPs can suppress ovulation, but this is not their primary mode of action.

Adverse Reactions of Oral Contraceptive Pills

While oral contraceptive pills are generally safe and well-tolerated, they can cause adverse reactions in some women. It’s important to be aware of these potential side effects and to discuss any concerns with your healthcare provider.

Adverse Reactions of COCs

Common side effects of COCs include nausea, breast tenderness, headaches, and mood changes. More serious but rare side effects include blood clots, stroke, and heart attack, particularly in women who smoke and are over 35 years old.

Adverse Reactions of POPs

POPs can cause irregular menstrual bleeding, breast tenderness, and headaches. Because they do not contain estrogen, they have a lower risk of serious side effects compared to COCs.

Non-Contraceptive Benefits

They offer regulatory benefits on menstrual cycles, alleviation from menstrual cramps, and management of acne and hirsutism​4​.

Recent Advancements

New formulations have emerged allowing more individualized prescriptions based on women’s specific needs and responses, enhancing individualization and compliance​5​.

Contraindications of Oral Contraceptive Pills

Absolute Contraindications: Include a history of thromboembolic disorders, stroke, coronary artery disease, breast cancer, liver tumors, or undiagnosed abnormal uterine bleeding.

Relative Contraindications: Include conditions like migraines, diabetes, gallbladder disease, and a history of depression, where the benefits and risks need to be carefully weighed.

Contraindications of COCs

COCs are contraindicated in women who have a history of blood clots, stroke, or heart attack. They are also contraindicated in women who have certain types of cancer, liver disease, or uncontrolled high blood pressure and in women who smoke and are over 35 years old.

Contraindications of POPs

POPs are contraindicated in women who have breast cancer or liver disease. Unlike COCs, they can be safely used by women who have a history of blood clots, stroke, or heart attack.

Drug Interactions of Oral Contraceptive Pills

Drug Interactions of COCs

Certain medications can decrease the effectiveness of COCs, including some anticonvulsants, antifungals, and HIV medications. COCs can also increase the blood levels of certain drugs, such as cyclosporine and theophylline, which can increase the risk of side effects from these drugs.

Drug Interactions of POPs

Like COCs, certain medications can decrease the effectiveness of POPs, including some anticonvulsants, antifungals, and HIV medications. However, POPs have fewer drug interactions compared to COCs.


Oral contraceptive drugs, by modulating the hormonal milieu, provide a reliable contraception method alongside other non-contraceptive benefits. The continuous advancements in formulation development are geared towards enhancing individualization and compliance. However, like any other pharmacological agents, they come with potential adverse effects and contraindications, underscoring the importance of a well-informed prescription and administration guided by healthcare professionals.

Disclaimer: This article is for informational purposes only and should not be taken as medical advice. Always consult with a healthcare professional before making any decisions related to medication or treatment.


1. Are oral contraceptive pills 100% effective?

No method of contraception is 100% effective. However, when taken correctly, oral contraceptive pills are over 99% effective at preventing pregnancy.

2. Can I use oral contraceptive pills if I’m breastfeeding?

Yes, you can use oral contraceptive pills while breastfeeding. However, it’s generally recommended to use progestin-only pills as they do not affect milk production.

3. Can oral contraceptive pills cause weight gain?

Some women may experience slight weight gain when they start taking oral contraceptive pills due to water retention. However, long-term weight gain is not a common side effect of these pills.

4. Can I get pregnant as soon as I stop taking oral contraceptive pills?

Yes, you can get pregnant as soon as you stop taking oral contraceptive pills. If you don’t want to get pregnant, you should use another method of contraception.

5. Can oral contraceptive pills protect against sexually transmitted infections (STIs)?

No, oral contraceptive pills do not protect against STIs. To protect against STIs, use a barrier method of contraception, such as condoms.

6. Can I skip my period with oral contraceptive pills?

Yes, you can skip your period with certain types of oral contraceptive pills. This is usually done by skipping the placebo pills in your pill pack and starting a new pack right away.

Key Points:

  1. Oral contraceptive pills (OCPs) are of four types: Combination pills, Mini pills, Post-coital pills, and Centchroman (non-hormonal).
  2. Combination pills are the most popular and effective contraceptive method, with a 99-99.5% success rate.
  3. Combination pills are available in three formulations: Monophasic, Biphasic, and Triphasic, with varying amounts of estrogen and progestin in each phase.
  4. OCPs work by suppressing gonadotropin secretion, inhibiting ovulation, developing endometrial atrophy, producing viscous cervical mucus, and interfering with ovum and sperm transport.
  5. Some common side effects of OCPs include nausea, migraine, breast tenderness, mild oedema, headache, and mood changes. Other adverse effects include weight gain, abnormal menstrual bleeding, and increased incidence of thromboembolism, hypertension, and cancers.
  6. The World Health Organization has developed a list of absolute and relative contraindications to the use of combined OCPs, based on the available evidence of risks.
  7. Mini pills, which contain only progestin, are given in cases where estrogens are contraindicated and are prescribed soon after delivery.
  8. Mini pills have a lower success rate (98.3%) compared to combination or phasic pills.
  9. Post-coital pills are taken after unprotected sex to prevent pregnancy.
  10. Post-coital (morning-after) pills are emergency contraceptives that can be used after unprotected sex to prevent pregnancy.
  11. Centchroman is a non-hormonal contraceptive pill that works by inhibiting ovulation and thickening cervical mucus. It is sometimes used as an alternative to hormonal contraceptives.
  12. Oral contraceptive pills can also provide other benefits besides contraception, such as reducing the risk of ovarian and endometrial cancer, improving acne, and reducing menstrual cramps and bleeding.
  13. The effectiveness of oral contraceptive pills can be reduced by certain medications, such as antibiotics and anticonvulsants, as well as by vomiting or diarrhea.
  14. Women who experience certain medical conditions, such as liver disease, migraines with aura, or a history of blood clots, may need to avoid or be cautious when using oral contraceptive pills.
  15. Women who use oral contraceptive pills should be advised to monitor for side effects and to report any concerning symptoms, such as severe headaches or chest pain, to their healthcare provider.

Quiz (Please note that the quiz can only be accessed on desktops/laptops)

[qsm quiz=8]

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always seek the advice of a healthcare provider with any questions regarding a medical condition.

Leave a Reply

Your email address will not be published. Required fields are marked *