Slynd: The Progestin-Only Pill You May Not Have Heard Of… and it’s my personal favorite (Part 1)
One of the things I love most about practicing integrative women's health is helping women understand that there are more options than they think — especially when it comes to birth control.
Most women are familiar with the combined oral contraceptive pill — the one that contains both estrogen and progestin. But far fewer have heard of Slynd, a progestin-only pill that I find myself recommending more and more in my practice.
This is Part 1 of a two-part series. Today we're covering what Slynd is, how it works, and what makes it different from other birth control pills. In Part 2, we'll dive into who might benefit most from it — including women with PCOS, heavy periods, PMDD and those in perimenopause or postmenopause on hormone replacement therapy.
Let's get into it.
What Is Slynd?
Slynd is the brand name for drospirenone 4 mg, a progestin-only oral contraceptive. It was FDA-approved in 2019 as the first progestin-only pill containing drospirenone — making it a relatively new addition to the contraceptive landscape.
Unlike the traditional combined oral contraceptive pill (which contains both estrogen and a progestin), Slynd contains no estrogen whatsoever. This is an important distinction, and one that opens the door for women who can't or prefer not to use estrogen-containing contraceptives.
Slynd comes in a 28-day pack: 24 active white tablets and 4 inactive green tablets. The 4-day hormone-free interval is designed to allow for a scheduled withdrawal bleed, similar to the placebo week in combined pills.
How Does Slynd Work?
Slynd's primary mechanism of action is ovulation suppression. Unlike the older progestin-only pill (norethindrone), which does not reliably suppress ovulation and works mainly by thickening cervical mucus and thinning the uterine lining, Slynd consistently suppresses ovulation — making it more similar in efficacy to combined oral contraceptive pills.
This is possible because drospirenone has a long half-life of approximately 25–30 hours, which provides sustained hormonal activity throughout the day and more reliably inhibits the LH surge needed for ovulation.
In addition to ovulation suppression, Slynd also thickens cervical mucus, which further reduces the chance of sperm reaching an egg.
The 24-Hour Missed Pill Window — A Game Changer
One of the most clinically meaningful differences between Slynd and other progestin-only pills is its missed pill window.
The older norethindrone progestin-only pill has a strict 3-hour window — meaning if you take it more than 3 hours late, you need to use backup contraception for 48 hours, according to ACOG. For many women, this level of precision is simply not always realistic day-to-day.
Slynd, by contrast, has a 24-hour missed pill window. This means as long as you take it within 24 hours of your usual time, you're still protected. You only need to use backup contraception if you miss two or more active pills in a row. Of course, daily use at the same time each day is always recommended for the best efficacy.
This flexibility is a significant quality-of-life improvement — and may improve real-world effectiveness by reducing the margin for error.
What Is Drospirenone, and Why Does It Matter?
Drospirenone is a synthetic progestin that is structurally similar to spironolactone — a medication many women know as a diuretic and androgen blocker (shoutout to my ladies who have had success with spironolactone for their acne!). This structural similarity gives drospirenone two additional properties that set it apart from other progestins:
1. Anti-Androgenic Effects
Drospirenone has meaningful anti-androgenic activity. It blocks the androgen receptor, inhibits 5-alpha-reductase (the enzyme that converts testosterone to its more potent form, dihydrotestosterone), and reduces androgen production from the ovaries.
In practical terms, this means Slynd may have the added benefit of helping to treat androgen-driven symptoms like acne and excess hair growth (hirsutism). It's worth noting that this anti-androgenic potency is roughly one-third that of cyproterone acetate, so it is real but not as potent as dedicated anti-androgen therapies. Nuance is important here — it may be a benefit, but should not be framed as a primary acne or PCOS treatment without that context.
2. Anti-Mineralocorticoid (Diuretic-Like) Effects
Drospirenone is also an aldosterone antagonist — meaning it blocks the mineralocorticoid receptor, similarly to how spironolactone works. This gives it a mild diuretic effect, which may help prevent bloating and fluid retention that some, but not all, women may experience from micronized progesterone or other forms of progestins.
An important safety consideration here: because of this anti-mineralocorticoid activity, drospirenone can increase serum potassium levels. Women taking medications that also raise potassium — such as ACE inhibitors, ARBs, potassium-sparing diuretics, or NSAIDs used regularly — should discuss this with their provider before starting Slynd. Potassium levels may need to be monitored, and this is why its important to work with someone who understands the nuances of these medications! If you’d like to work with me in 2027, join my waitlist here.
Who Are Good Candidates for a Progestin-Only Pill Like Slynd?
Because Slynd contains no estrogen, it is a particularly good option for women who cannot or prefer not to use estrogen-containing contraceptives, including:
Women who smoke and are over 35 (combined pills significantly increase clot risk in this group)
Women with a personal history of blood clots (venous thromboembolism)
Women with migraine with aura (estrogen-containing pills are generally contraindicated)
Breastfeeding women (progestin-only pills are generally considered compatible with breastfeeding)
Women who simply prefer to avoid estrogen for personal or health reasons
And as we'll explore in Part 2 — women with PCOS, heavy menstrual bleeding, and peri/postmenopausal women on HRT who need progesterone opposition but don't tolerate micronized progesterone. Drospirenone may also have benefits for women with PMDD, though most of the evidence to date is from drospirenone combined with estrogen (like Yaz), which is FDA-approved for PMDD — not the progestin-only formulation specifically. The mechanism, however, is physiologically sound.
The Bottom Line
Slynd is generally well-tolerated, estrogen-free contraceptive option with a more forgiving dosing schedule than older progestin-only pills, meaningful anti-androgenic and diuretic-like properties, and reliable ovulation suppression. It's not a one-size-fits-all solution — but for the right woman, it can be a really wonderful fit.
Part 2 is coming later this week — where we'll explore who may benefit most from Slynd, including some specific patient populations that I find myself counseling on this option regularly.
If you'd like to work together to explore what birth control option is right for you, I'd love to support you. You can schedule an Individualized Educational Consultation with me here, or join my waitlist here to be one of the first notified when I open my integrative women's health practice in 2027.
*This is educational content only. Not a substitute for medical care. Views are my own and separate from my institution and employer. Always discuss individual health concerns with your personal healthcare provider.
References
Palacios S, Colli E, Regidor PA. Multicenter, phase III trials on the contraceptive efficacy, tolerability and safety of a new drospirenone only pill. Acta Obstet Gynecol Scand. 2019;98(12):1549–1557. https://pubmed.ncbi.nlm.nih.gov/31321765/
Kimble T, Burke AE, Barnhart KT, et al. A 1-year prospective, open-label, single-arm, multicenter, phase 3 trial of the contraceptive efficacy and safety of the oral progestin-only pill drospirenone 4 mg using a 24/4-day regimen. Contracept X. 2020;2:100020. https://pubmed.ncbi.nlm.nih.gov/32550535/
ACOG: Progestin-Only Hormonal Birth Control: Pill and Injection https://www.acog.org/womens-health/faqs/progestin-only-hormonal-birth-control-pill-and-injection