Medicine 3: Combined Oral Contraceptives

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Medicine 3: Combined Oral Contraceptives

What is it?

Combination birth control pills, also known as the pill, are oral contraceptives that contain estrogen and a progestin.

Combination birth control pills come in different mixtures of active and inactive pills, including:

Conventional pack: One common type contains 21 active pills and seven inactive pills. Inactive pills do not contain hormones. Formulations containing 24 active pills and four inactive pills, known as a shortened pill-free interval, are also available. Some newer pills may contain only two inactive pills. You take a pill every day and start a new pack when you finish the old one. Packs usually contain 28 days of pills. Bleeding may occur every month during the time when you take the inactive pills that are at the end of each pack.

Extended-cycle pack: These packs typically contain 84 active pills and seven inactive pills. Bleeding generally occurs only four times a year during the seven days you take the inactive pills.

Continuous-dosing pack: A 365-day pill also is available. You take this pill every day at the same time. For some people, periods stop altogether. For others, periods become significantly lighter. You do not take any inactive pills.¹

How does it work?

In women with primary dysmenorrhea, OCPs thin the endometrium, thereby reducing the amount of bleeding and inhibiting the metabolism of arachidonic acid to prostaglandin, effectively relieving cramping and pain.²

What is the efficacy?

Methods: The five studies included randomized controlled trials and systematic reviews that tested different combined oral contraceptive (COC) pills—ranging from low-dose and ultra-low-dose formulations to newer combinations—on women and adolescents with dysmenorrhea. Participants were randomly assigned to receive either a COC, a placebo, or another active pill for several menstrual cycles, with some trials also comparing continuous or extended regimens to the standard cyclic schedule. Pain relief was measured using standardized pain scores, visual analogue scales (VAS), quality-of-life questionnaires.^3,4,5,6,7

Results: Across the studies, COCs consistently reduced period pain more effectively than placebo, with improvements seen in pain scores, fewer painful days, and reduced need for pain medication. Extended or continuous pill regimens often led to even fewer days of discomfort compared to the standard monthly cycle. Mild side effects like irregular bleeding and nausea were more common than with placebo.

Conclusions: Overall, combined oral contraceptives are effective in easing period pain, with extended regimens offering added relief for some. They are generally safe, with most side effects being mild and manageable, making them a useful option for managing dysmenorrhea.³

Side-effects:

Short-term effects: Breast tenderness, nausea, headaches, bloating, and unscheduled bleeding.

Long-term effects: Increased risk of venous and arterial thromboembolism (deep vein thrombosis, pulmonary embolism, myocardial infarction, stroke), mild increase in blood pressure, and possible increases in breast and cervical cancer risk.⁸

References

1. Cooper DB, Patel P. Oral Contraceptive Pills. [Updated 2024 Feb 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan– [cited 2025 May 16]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430882/

2. Casper RF. Progestin-only pills may be a better first-line treatment for endometriosis than combined estrogen-progestin contraceptive pills. Fertility and sterility. 2017 Mar 1;107(3):533-6.

1. Davis AR, Westhoff C, O’Connell K, Gallagher N. Oral contraceptives for dysmenorrhea in adolescent girls: a randomized trial. Obstet Gynecol. 2005 Jul;106(1):97–104. doi:10.1097/01.AOG.0000165826.03915.65.

2. Schroll JB, Black AY, Farquhar C, Chen I. Combined oral contraceptive pill for primary dysmenorrhoea. Cochrane Database of Systematic Reviews. 2023(7).

3. Harada T, Momoeda M. Evaluation of an ultra-low-dose oral contraceptive for dysmenorrhea: a placebo-controlled, double-blind, randomized trial. Fertility and sterility. 2016 Dec 1;106(7):1807-14.

4. Damm T, Lamvu G, Carrillo J, Ouyang C, Feranec J. Continuous vs. cyclic combined hormonal contraceptives for treatment of dysmenorrhea: a systematic review. Contraception: X. 2019 Jan 1;1:100002.

5. Osuga Y, Kobayashi T, Hirakawa A, Takayanagi T, Nogami M, Tayzar K, Mochiyama T, Hirayama M, Foidart JM, Harada T. Efficacy and safety of estetrol (15 mg)/drospirenone (3 mg) combination in a cyclic regimen for the treatment of primary and secondary dysmenorrhea: a multicenter, placebo-controlled, double-blind, randomized study. Fertility and Sterility. 2025 Apr 1;123(4):700-8.

6. Edwards M, Can AS. Progestins. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan [cited 2025 May 16]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK563211/