Composition of Lo Loestrin Fe
Lo Loestrin Fe contains norethindrone acetate 1 mg and ethinyl estradiol 10 micrograms as its active hormonal ingredients, along with ferrous fumarate tablets for the placebo phase.
Lo Loestrin Fe is a combined oral contraceptive (COC) that features one of the lowest doses of ethinyl estradiol available in any oral contraceptive on the market. Its composition includes:
Active Hormonal Components
Norethindrone acetate: 1 mg
- A first-generation progestin derived from testosterone
- Functions as the progestin component that inhibits ovulation
Ethinyl estradiol: 10 micrograms
- A synthetic estrogen component
- Ultra-low dose compared to other COCs which typically contain 20-35 μg
Regimen Structure
Lo Loestrin Fe is packaged in a 28-day regimen consisting of:
- 24 blue active tablets containing both norethindrone acetate and ethinyl estradiol
- 2 white tablets containing only ethinyl estradiol (10 μg)
- 2 brown tablets containing ferrous fumarate (iron supplement)
Mechanism of Action
As a combined oral contraceptive, Lo Loestrin Fe works through several mechanisms 1:
- Inhibiting gonadotropin-releasing hormone, follicle-stimulating hormone, and luteinizing hormone
- Preventing ovulation
- Decreasing ovarian androgen production
- Increasing sex hormone-binding globulin
- Reducing free testosterone
- Reducing 5α-reductase activity
- Blocking androgen receptors
Clinical Context
Lo Loestrin Fe is FDA-approved for contraception and is one of four COCs that are also approved for the treatment of acne in women who desire oral contraception 1. The ultra-low dose of ethinyl estradiol (10 μg) makes it one of the lowest estrogen-containing COCs available, which may be beneficial for women who are sensitive to estrogen-related side effects.
Safety Considerations
- The low estrogen dose may be associated with a potentially lower risk of estrogen-related side effects compared to higher-dose formulations
- However, like all COCs, it carries risks including venous thromboembolism, with risk varying by estrogen dose and progestin type 1
- Contraindicated in women with certain conditions including history of thromboembolism, uncontrolled hypertension, and certain types of migraines 1
Lo Loestrin Fe represents an ultra-low-dose oral contraceptive option that maintains contraceptive efficacy while potentially minimizing estrogen-related adverse effects 2.