Meet Slynd: A Novel Progestin-Only Pill

What’s this new pill?

Slynd® is the new progestin-only oral contraceptive approved by the FDA in May 2019. This novel progestin-only pill (POP) contains drospirenone 4 mg in each active tablet, which is a higher dose than what is found in drospirenone-containing combined oral contraceptives (COCs). 

Table 1. Products with drospirenone.

This will be the second POP formulation available, in addition to the many norethindrone 0.35 mg products currently available.

What are the features of this new pill?

This pill provides pregnancy prevention with a 24/4 dose regimen. In the ongoing evolution of contraception, the goal has always been to improve efficacy as well as minimizing adverse events. Estrogen dose reduction and shortening of hormone-free intervals have been helpful to meet these goals. As a result, Slynd was developed with a 24/4 dose regimen which provides a more stable hormonal timeframe compared to traditional 21/7 dose regimens, achieving greater pituitary and ovarian suppression. For this reason, the 24/4 regimen has less hormone withdrawal effect and improves pelvic pain, headaches, breast tenderness, and bloating symptoms that are reported during the hormone-free days with 21/7 regimens.  

Figure 1. Slynd pill pack containing 24 active pills and 4 inactive pills.

(Image credit: slynd.com)

Slynd also allows a 24-hour missed pill window which improves reliability and bleeding profiles in the event of a missed dose. One study compared two arms — one with four missed doses (four 24-hour delays) and the other with no missed dose during the cycle. Even with four missed doses in the cycle, there was adequate ovarian suppression and the same follicular size was observed in both arms.

Drospirenone inhibits ovulation by suppressing luteinizing hormone (LH) secretion. Additionally, by modifying cervical mucus, it reduces sperm transport and thus prevents fertilization. Unlike other conventional synthetic progestins, drospirenone has a similar profile to endogenous progesterone. As an analogue of 17-alpha spironolactone, drospirenone has anti-mineralocorticoid and anti-androgenic activity. Due to the anti-mineralocorticoid activity, it increases urinary sodium and serum aldosterone. Therefore, compared to other COCs causing fluid retention and edema, drospirenone has an ability to reduce blood pressure. 

 

Should we be worried about blood clots with drospirenone?

Drospirenone was first introduced to the market in combination with low dose ethinyl estradiol as a contraceptive well suited for women with premenstrual dysphoric disorder (PMDD), moderate acne, polycystic ovarian syndrome and hirsutism. 

While the FDA is concerned about the potential correlation between contraceptives containing drospirenone and blood clots, the overall result of two prospective multicenter phase III studies reported no single case of venous thromboembolism (VTE) in patients who used POP. FDA has funded a study to investigate the correlation, and still is reviewing other clinical trials. In 2011, the FDA reported that “preliminary results of the FDA-funded study suggest an approximately 1.5-fold increase in the risk of blood clots for women who use drospirenone-containing birth control pills compared to users of other hormonal contraceptives.” 

Other studies have shown use of drospirenone-containing COCs was not associated with increased risk of thromboembolic events compared to other COCs containing other progestins. Due to data limitations, the causality is still unclear, and FDA will provide updates once available. 

While there is an increase in the relative risk of this rare adverse event with COCs containing drospirenone, the incidence is still very low and much lower than pregnancy and postpartum periods. ACOG’s Committee on Gynecologic Practice has concluded that the risk of thromboembolism in patients who use drospirenone-containing COCs is very low.  

It is unknown whether Slynd increases the risk of VTEs, however, any potential risk with this POP is expected to be lower than COCs containing drospirenone. 

 

Which patients should not use this pill?

Drospirenone is contraindicated in women with positive or unknown antiphospholipid antibodies, ischemic heart disease, stroke, current or history of breast cancer, hepatocellular adenoma, malignant hepatoma, and severe hepatitis. Clinicians should use this medication with caution in patients who are taking other medications that can predispose them to hyperkalemia, or monitor potassium level.

The drug interaction profile is similar to drospirenone-containing COCs. Although drospirenone is metabolized independently of P450 enzymes, it is a minor substrate of CYP3A4. It is recommended to avoid use in patients taking strong 3A4 inhibitors to prevent hyperkalemia. Strong P450 and P-glycoprotein transporter inhibitors and inducers can affect the serum concentration, efficacy, and adverse effects. 

 

What’s the bottom line for place in therapy?

In conclusion, Slynd can be used in most patients and will be an important option for patients with contraindications to estrogen — including history of high blood pressure or smoking above age 35 — PMDD, as well as patients desiring contraception without androgenic effects, such as those with acne or polycystic ovary syndrome (PCOS).

 

References:

1. Mishell DR. “YAZ and the Novel Progestin Drospirenone.” The Journal of Reproductive Medicine 2008.
2. Machado RB, et al. “Drospirenone/Ethinylestradiol: A Review on Efficacy and Noncontraceptive Benefits.” Womens Health 2011;7(1)19–30.
3. Bachmann G, Kopacz S. “Drospirenone/Ethinyl Estradiol 3 Mg/20 Mug (24/4 Day Regimen): Hormonal Contraceptive Choices – Use of a Fourth-Generation Progestin.” Patient Preference and Adherence, 2009 
4. Palacios S, et al. “Multicenter, Phase III Trials on the Contraceptive Efficacy, Tolerability and Safety of a New Drospirenone‐Only Pill.” Acta Obstetricia Et Gynecologica Scandinavica 2019.
5. Center for Drug Evaluation and Research. “Risk of Blood Clots with Birth Control Pills Containing Drospirenone.” FDA Website Available from: https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-safety-review-update-possible-increased-risk-blood-clots-birth-control.
6. American College of Obstetricians and Gynecologists. Risk of venous thromboembolism among users of drospirenone-containing oral contraceptive pills. Committee Opinion No. 540. Obstet Gynecol 2012;120:1239–42. Available at: https://www.acog.org/Clinical-Guidance-and-Publications/Committee-Opinions/Committee-on-Gynecologic-Practice/Risk-of-Venous-Thromboembolism.
7. Drugs.com. Exeltis USA, Inc. Announces the Approval of Slynd (drospirenone), the First and Only Progestin-Only Pill Providing Pregnancy Prevention with a 24/4 Dosing Regimen and 24-hour Missed Pill Window. 2019. [online]
8. Slynd (drospirenone) [prescribing information]. Florham Park, NJ; Exeltis USA, Inc.; May 2019.
9. Duijkers IJ, Heger-Mahn D, Drouin D, Colli E, Skouby S. Maintenance of ovulation inhibition with a new progestogen-only pill containing drospirenone after scheduled 24-h delays in pill intake. Contraception 2016;93(4):303–309.
10. CDC. US Medical Eligibility Criteria for Contraceptive Use, 2016. MMWR Recomm Rep 2016;65Available at: https://www.cdc.gov/reproductivehealth/contraception/mmwr/mec/appendixc_tableC1.html

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About the Author:

Lida Binesheian, PharmD, CACP is a Clinical Pharmacist and Certified Anticoagulation Care Provider based in Austin, Texas.