From the Guidelines
Estradiol in a combination birth control pill is typically in the form of ethinyl estradiol, a synthetic form of the female hormone estrogen, usually dosed between 10-35 micrograms per pill. When taking a combination pill, the estradiol component works together with a progestin (synthetic progesterone) to prevent pregnancy by stopping ovulation, thickening cervical mucus to block sperm, and thinning the uterine lining to prevent implantation 1. The estradiol component is responsible for regulating your menstrual cycle and preventing breakthrough bleeding, while the progestin component primarily prevents ovulation.
Some key points to consider when taking a combination pill with estradiol include:
- The most common form of estradiol in combination pills is ethinyl estradiol, with doses ranging from 10-35 micrograms per pill 1
- The estradiol component can cause side effects such as nausea, breast tenderness, headaches, and blood clot risk, though modern pills use lower doses to minimize these effects 1
- If you experience concerning side effects, speak with your healthcare provider about switching to a different formulation with a different estradiol dose or type
- Combination pills do not protect against sexually transmitted infections (STIs) or human immunodeficiency virus (HIV), and a backup method such as condoms should be used for protection against STIs 1
It's essential to follow the prescribed dosage and regimen for your combination pill, and to discuss any concerns or side effects with your healthcare provider. They can help you determine the best course of action and ensure that you're using the most effective and safe form of birth control for your needs.
From the FDA Drug Label
CLINICAL PHARMACOLOGY Combination oral contraceptives act by suppression of gonadotropins. Kariva (desogestrel/ethinyl estradiol and ethinyl estradiol) Tablets provide two different regimens of ethinyl estradiol; 0.02 mg in the combination tablet [white] as well as 0. 01 mg in the light-blue tablet. Ethinyl estradiol is rapidly and almost completely absorbed. The pharmacokinetics of etonogestrel and ethinyl estradiol following multiple dose administration of Kariva® tablets were determined during the third cycle in 17 subjects Ethinyl estradiol Day Dose mg Cmax pg/mL Tmax h t1/2 h AUC0–24 pg/mL•hr CL/F L/h 1 0.02 51.9 (15.4) 2.9 (1.2) 16.5 (4.8) 566 (173)a 25.7 (9.1)
Ethinyl estradiol is a form of estrogen used in combination oral contraceptives.
- The combination pill contains 0.02 mg of ethinyl estradiol in the white tablet and 0.01 mg in the light-blue tablet.
- Ethinyl estradiol is rapidly and almost completely absorbed after oral administration.
- The pharmacokinetics of ethinyl estradiol were determined during the third cycle in 17 subjects, with a Cmax of 51.9 pg/mL and an AUC0-24 of 566 pg/mL·hr 2
From the Research
Definition of Estradiol
- Estradiol is a naturally occurring estrogen steroid hormone and a major female sex hormone [(3,4,5)].
- It is one of the three main types of estrogen, along with estrone and estriol [(4,5)].
Estradiol in Combination Pill
- Estradiol is used as an alternative to ethinyl estradiol (EE) in some combined oral contraceptives (COCs) [(3,4)].
- The use of estradiol in COCs has been shown to have similar efficacy and cycle control as EE-based COCs 3.
- Estradiol has a lower potency than EE and may be less stimulatory of coagulant proteins 4.
Comparison with Other Estrogens
- Estradiol has been compared to other estrogens, such as ethinyl estradiol (EE) and estetrol (E4), in terms of its structure-function relationships, receptor-binding affinity, potency, metabolism, pharmacokinetic parameters, and pharmacodynamics 4.
- Estradiol has a higher binding affinity for estrogen receptor (ER)β than EE, but a lower binding affinity for ERα 4.
- Estradiol undergoes extensive metabolism, similar to EE, while E4 produces only a limited number of metabolites 4.