Slynd: How Canada’s Estrogen-Free Birth Control Pill Works

Most birth control pills use two hormones, which is where the name “combined pill” comes from. Slynd uses one — a progestin called drospirenone, with no estrogen at all. This makes Slynd a potentially suitable birth control option for people who have been advised to avoid estrogen, or would simply prefer a pill without it.

The change most people notice on Slynd is to their bleeding. Spotting between periods is common in the first few months, and it usually settles as your body adjusts. Over time, periods often become much lighter on Slynd, or stop altogether.

In this article, we cover what Slynd is, how it works, and how to take it, including the unusually forgiving 24-hour window it allows if a tablet is late. We also look at what to expect from your periods, the side effects worth knowing about, and what Slynd costs in Canada.

An Overview of Slynd Birth Control

Slynd is the brand name for drospirenone 4 mg tablets, a prescription birth control pill made by Duchesnay. Being progestin-only means it contains one hormone where a combined pill (such as Yaz, Yasmin and Mya) contains two. Slynd birth control has been available in Canada since 2022, and there’s no generic version on the market here.

A Slynd 28-day pack covers four weeks. 24 of the tablets are white and active, each containing 4 mg of drospirenone. The final 4 are green and contain no hormone at all. You take one tablet a day, and when a pack runs out, you start the next one the day after — there’s no break between packs.

Health Canada has approved Slynd for preventing pregnancy. Slynd is prescription-only, so you’ll need a doctor or authorized healthcare practitioner to prescribe it.

How Slynd Works

Drospirenone is a progestin — a lab-made version of progesterone, the hormone your body produces after ovulation each month. Slynd works mainly by using drospirenone to switch off ovulation. With no egg released, there’s nothing for sperm to fertilise. Drospirenone backs that up in two smaller ways: it thickens the mucus at the cervix so sperm find it harder to get through, and it thins the lining of the womb.

Slynd has an unusually forgiving missed-pill window. In the trials evaluating Slynd, ovulation stayed suppressed even when tablets were deliberately taken 24 hours late. That’s why Slynd allows a full day’s grace on a late tablet, whereas the older norethindrone pills have to be taken within three hours.

Drospirenone is chemically related to a diuretic called spironolactone, which gives it a mild effect on how your body handles salt, water, and potassium. For most people, that passes unnoticed and doesn’t cause any side effects. It’s also why Slynd carries some specific cautions for people with kidney, liver, or adrenal problems.

Taking Slynd: The 24/4 Pack and the 24-Hour Window

Slynd 4 mg is taken as one tablet a day, in pack order, with no break between packs. Here are some general guidelines for taking it:

• Pick a time and keep to it: The 24-hour window is a safety margin, not a schedule. Taking Slynd at roughly the same time each day is still the simplest way to stay protected.
• If you’re late or miss one white tablet: Take it as soon as you remember and carry on with one a day until the pack is finished. No backup contraception is needed — this is the 24-hour window doing its job.
• If you miss two or more white tablets: Take the last missed tablet as soon as you can, then carry on as normal. Use a backup method such as condoms for the next 7 days if you have sex during that time.
• If you miss a green tablet: The green tablets are the placebo pills in the pack and contain no hormone, so missing one doesn’t affect your protection. Skip the green pill(s) you missed and carry on with one tablet a day until the pack is finished.
• If you’re sick: Vomiting or diarrhoea within 3 to 4 hours of a Slynd tablet can stop it being absorbed, which counts as a missed tablet (so take the next day’s tablet as soon as you can).
• Starting a pack for the first time: Slynd is designed to be started on the first day of your period, taking the first white tablet that day. If you’re switching from another method or starting at a different point in your cycle, ask your doctor or pharmacist whether you need backup contraception for the first week.
• Medicines that can reduce effectiveness: Some epilepsy medicines, the antibiotic rifampicin, and the herbal remedy St John’s wort can make Slynd less effective. Tell your doctor or pharmacist what else you take, including any supplements.

How Effective Is Slynd?

Slynd is a reliable contraceptive. However, like all birth control pills, its effectiveness relies on taking it consistently. Researchers measure the effectiveness of birth control pills like Slynd in two ways: Perfect use means the method is used exactly as directed, every time; typical use allows for real life and the occasional late tablet.

Slynd’s own clinical trials produced different effectiveness figures in different populations. In the two European studies, fewer than 1 in 100 women became pregnant over a year of use. The North American study, which enrolled a wider range of body weights, found closer to 2 in 100. Those figures come from monitored trial conditions, so they sit closer to the perfect-use end than to typical use.

A more forgiving missed-pill window sounds as though it ought to mean fewer unintended pregnancies in practice, but that hasn’t been shown directly. What can be said is that forgetting tablets is the commonest way any pill fails, and Slynd tolerates a late dose better than most other birth control pills.

Slynd and Your Periods

Spotting or bleeding between periods is usual in the early months of starting Slynd. In the clinical trials, 61.4% of women had unscheduled bleeding or spotting in the first cycle, falling to 40.3% by the thirteenth cycle. The pattern settles rather than vanishes, and for most people, the first few months are the worst of it.

Periods themselves tend to get lighter over time with Slynd, and for some people they stop altogether. That isn’t a sign anything has gone wrong. With less hormone reaching the lining of the womb, there’s less to shed each month.

A missing period isn’t by itself a sign the Slynd pill has failed (especially if you’ve taken every tablet on time). If you’ve missed tablets, or you go two cycles with no bleeding at all, take a pregnancy test and check in with your doctor or pharmacist.

Slynd vs the Other Progestin-Only Pills

Canada has two kinds of progestin-only pill: Slynd, and the older norethindrone pills sold as Movisse, Maeve, and Jencycla.

Slynd vs Movisse and the Other Norethindrone Pills

Three things separate Slynd from norethindrone birth control pills.

• Timing: Slynd gives you a full day to take a late tablet. The norethindrone pills give you three hours, then 48 hours of backup contraception.
• The pack: Slynd runs on a 24/4 schedule with four hormone-free days built in. The norethindrone pills are taken continuously, with no inactive tablets at all.
• Cost: The norethindrone pills come as generics and are considerably cheaper. Slynd is brand-only in Canada.

If a daily alarm is something you’d rather not depend on, Slynd’s more forgiving window might be the reason to choose it. If cost is the deciding factor and you’re confident about timing, a norethindrone pill usually does the same job for less.

Slynd vs Yaz, Yasmin and Mya

These four pills share a progestin, which is why they’re often mentioned together, but they aren’t the same class of medication. Yaz, Yasmin and Mya are combined pills: they pair drospirenone with an estrogen, while Slynd doesn’t contain estrogen at all.

Combined pills carry a small increase in the risk of blood clots that progestin-only pills aren’t considered to share, which is why Slynd is an option for people who have been advised against taking estrogen. Yaz and Yasmin are also approved in Canada to treat moderate acne, while Slynd isn’t.

Slynd Side Effects and Safety

Most side effects of Slynd are mild, and they tend to ease over the first few months. In the clinical trials, only around a quarter of women reported any side effect at all.

The most commonly reported Slynd side effects include:

• Acne
• Headache
• Breast tenderness or pain
• Period pain
• Nausea
• A lower sex drive

Changes to bleeding are the most common Slynd side effect, which we have already covered in depth earlier in this article.

Weight gain is one of the most common worries about hormonal birth control. Slynd’s trials recorded no meaningful change in body weight, and broader reviews of hormonal contraception haven’t found that it causes weight gain.

Drospirenone (the active ingredient in Slynd) can raise the level of potassium in your blood. This is why your doctor may want a blood test before you start and during your first month, especially if you take any medicines like potassium-sparing diuretics, potassium supplements, ACE inhibitors, angiotensin-II receptor antagonists, or aldosterone antagonists.

Who Should Not Take Slynd

Doctors usually don’t prescribe Slynd for people who have:

• Kidney disease or reduced kidney function
• Reduced adrenal gland function
• Had cervical cancer, or another cancer sensitive to progestin
• Liver problems, including liver tumours
• Experienced unexplained bleeding from the vagina

Because Slynd contains no estrogen, several of the cautions that rule out a combined pill don’t apply. But that’s a conversation to have with a doctor who knows your history rather than an assumption to make on your own.

Slynd Cost, Coverage, and Access in Canada

Since Slynd is taken continuously, it’s an ongoing monthly purchase rather than a one-off course. What you pay for Slynd varies by province, pharmacy, and insurance, so ask your pharmacist for a current figure.

Slynd is brand-only in Canada, with no generic competing with it. As a result, it usually costs more than the older norethindrone pills. Coverage can differ sharply depending on where you live. Slynd appears on BC PharmaCare’s list of covered contraceptives as a full benefit. Elsewhere, prescription contraception is gradually becoming free under the federal pharmacare plan.

Slynd is prescription-only across Canada. You can see your family doctor, visit a walk-in clinic, or speak to a doctor online with Walk In.

Frequently Asked Questions

Can you take Slynd continuously and skip the inactive pills? 

Some people ask about running packs together to avoid a bleed. Slynd’s instructions say to take every tablet in the pack, in order, without skipping days, so it isn’t something to try on your own. If avoiding a monthly bleed matters to you, raise it with your doctor.

Does Slynd cause weight gain? 

Weight gain was reported by around 2% of women in the Slynd clinical trials, which is in the range you’d expect from ordinary fluctuation over a year. Drospirenone, the active ingredient in Slynd, tends to reduce fluid retention rather than cause it.

Does Slynd help with acne? 

Slynd isn’t approved for acne in Canada, and there isn’t good evidence it clears breakouts. Yaz and Yasmin do carry a Canadian acne approval, so if acne matters alongside contraception, it’s worth speaking with your doctor.

Can Slynd be used for endometriosis, PCOS, PMDD, or perimenopause? 

Slynd is not an approved treatment for any of those conditions in Canada. Progestin-only pills are sometimes prescribed off-label for symptoms in endometriosis, PCOS, PMDD, or perimenopause, but the evidence specific to drospirenone on its own is limited.

Is Slynd a good birth control pill? 

Most people who start taking Slynd carry on with it. Around a quarter reported a side effect of some kind, and roughly 3.5% stopped because of bleeding changes (which is the most common complaint you’ll find in Slynd birth control reviews).

Slynd vs Micronor — are they the same? No, and Micronor is no longer sold in Canada. Micronor contained norethindrone, a different progestin, with a much shorter missed-pill window. The norethindrone pills still available here are Movisse, Maeve, and Jencycla.

Is Slynd Right for You?

Slynd is the one birth control pill in Canada that combines a modern progestin with no estrogen at all. This can make it a good choice for people who have been told to avoid estrogen or who would prefer not to take a combined pill.

Slynd pros and cons tend to centre on two things. In its favour: no estrogen, a full day’s grace on a late tablet, and full coverage in BC. Against it: irregular bleeding in the early months, a brand-only price outside BC, and no acne benefit to speak of.

Whether Slynd suits you depends on your personal health history and what you want from your contraception. That’s something a doctor from Walk In can help you weigh up.

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