What is desogestrel and how does it work?
Desogestrel is a synthetic progestin that belongs to the third generation of progestogens used in hormonal contraception. It is known for high progestational activity and low androgenic properties, which may reduce side effects like acne and weight gain associated with older progestins. When taken orally, it is converted to its active form, etonogestrel.
A primary way desogestrel works, especially in the progestogen-only pill (POP), is by strongly inhibiting ovulation. It does this by suppressing hormones (GnRH, LH, and FSH) that are necessary for egg development and release.
Besides preventing ovulation, desogestrel also:
- Thickens cervical mucus: This makes it harder for sperm to reach the uterus.
- Changes the uterine lining: This makes it less suitable for a fertilized egg to implant.
Desogestrel in different contraceptive forms
Desogestrel is found in two main types of birth control pills:
- Combined Oral Contraceptives (COCs): These pills contain desogestrel and an estrogen, typically ethinyl estradiol. They usually involve taking active pills for 21 days followed by a 7-day break or placebo pills, during which bleeding occurs. COCs are very effective but may have cardiovascular risks for certain individuals.
- Progestogen-Only Pills (POPs) or 'Mini-pills': Desogestrel is also used alone in a daily pill, often at a 75-microgram dose. These are taken continuously. Since they don't contain estrogen, they are suitable for women who cannot use combined pills due to health reasons, such as smokers over 35 or those who are breastfeeding.
Benefits and considerations of desogestrel
Benefits:
- Estrogen-free: A good option for women with contraindications to estrogen, like a history of blood clots or certain types of migraines.
- Safe for breastfeeding: Does not negatively impact milk supply.
- May improve menstrual symptoms: Can help with heavy or painful periods and may stop periods for some users.
- Flexible dosing (for some POPs): Some desogestrel mini-pills allow for a 12-hour window for taking the pill daily, unlike the stricter 3-hour window of older mini-pills.
Considerations:
- Irregular bleeding: Changes in bleeding patterns, including spotting, are common, especially initially.
- Other side effects: Headaches, nausea, and breast tenderness are also reported.
- Blood clot risk: While generally lower with POPs, some desogestrel-containing combined pills may have a slightly higher risk of non-fatal blood clots compared to those with older progestins.
- Ectopic pregnancy: In the rare instance of pregnancy on the desogestrel-only pill, there is a slightly increased chance of it being ectopic.
Comparison of Desogestrel vs. Levonorgestrel
| Feature | Desogestrel | Levonorgestrel |
|---|---|---|
| Generation | Third-generation synthetic progestin | Second-generation synthetic progestin |
| Androgenic Activity | Very low androgenic activity | Higher androgenic activity compared to desogestrel |
| Primary Mechanism (POP) | Potent inhibition of ovulation | Primarily thickens cervical mucus; less consistent ovulation inhibition |
| Thromboembolic Risk | Possibly higher risk of non-fatal blood clots with combined pills vs. levonorgestrel | Generally considered to have a lower risk of blood clots compared to third-generation progestins |
| Metabolic Impact | Minimal negative impact on lipid metabolism | More likely to have negative effects on lipid metabolism |
Drug interactions and contraindications
Certain medications and supplements can affect how well desogestrel works. Drugs that increase liver enzymes, such as some epilepsy and tuberculosis treatments, can speed up the breakdown of desogestrel. St. John's wort, an herbal supplement, can also interfere with its action. Always inform your healthcare provider about all medications and supplements you are taking.
Combined pills with desogestrel are not suitable for individuals with a history of blood clots, certain heart conditions, uncontrolled high blood pressure, or for smokers over 35. Desogestrel-only pills have their own contraindications, including current breast cancer.
Conclusion
Desogestrel is a notable third-generation progestin that provides an effective contraceptive option, particularly for individuals who cannot use estrogen-containing methods. Its strong ability to prevent ovulation, especially in the progestogen-only form, distinguishes it from older mini-pills. However, potential side effects and risks exist, including irregular bleeding and, rarely, more serious issues like blood clots. Discussing your medical history and contraceptive needs with a healthcare provider is crucial to determine if desogestrel is the right choice for you.
For comprehensive information on drug interactions, consult resources like the National Institute for Health and Care Excellence (NICE) guidelines.
