Does Annovera Carry a Risk of Blood Clots?
Annovera, a combined hormonal contraceptive ring containing segesterone acetate and ethinyl estradiol, carries a boxed warning for serious cardiovascular risks, including blood clots (venous thromboembolism or VTE). The FDA requires this label due to evidence from clinical trials and post-marketing data showing an elevated risk compared to non-users, similar to other estrogen-containing contraceptives.[1][2]
In Annovera's Phase 3 trials (NCT01583235), VTE occurred in 3 cases out of 1,658 women (0.18% incidence), with rates aligning with combined oral contraceptives.[3] Real-world data from sources like the FDA Adverse Event Reporting System (FAERS) report additional cases, though causality is not always confirmed.
How Common Are Blood Clots with Annovera?
The absolute risk remains low: about 9-12 VTE events per 10,000 woman-years for users of estrogen-progestin contraceptives, versus 4-5 per 10,000 for non-users. Annovera's risk profile matches this class baseline, with no unique elevation in trials.[1][4] Most clots occur in the legs (DVT) or lungs (PE).
Who Is at Higher Risk for Clots from Annovera?
Risk increases with:
- Age over 35
- Smoking (especially 15+ cigarettes/day)
- Obesity (BMI ≥30)
- History of VTE, clotting disorders, or hypertension
- Recent surgery or immobility
- Genetic factors like Factor V Leiden
The prescribing information advises against use in these groups and recommends screening.[2]
What Symptoms Signal a Blood Clot?
Watch for leg swelling/pain, chest pain/shortness of breath, sudden severe headache, vision changes, or arm/leg pain. Seek immediate care if these appear, as clots can be fatal.[1][2]
How Does Annovera's Clot Risk Compare to Other Birth Control?
| Method | VTE Risk (per 10,000 woman-years) |
|--------|-----------------------------------|
| No hormones | 2-4 [4] |
| Annovera/Combined pills | 9-12 [1][4] |
| Progestin-only pills | 5-7 [4] |
| Patch (Xulane) | 9-12 [4] |
| IUD (Mirena) | 1-2 [4] |
| Copper IUD | <1 [4] |
Annovera matches combined pills and patches but exceeds progestin-only options, which lack estrogen.
Can You Still Use Annovera If Worried about Clots?
Discuss with a doctor for personalized risk assessment. Alternatives like progestin-only methods or non-hormonal IUDs have lower VTE risk. No specific Annovera patents cover clot mechanisms, but exclusivity runs through 2031.[5]
Sources:
[1] FDA Label for Annovera
[2] Annovera Prescribing Information
[3] ClinicalTrials.gov - Annovera Trials
[4] CDC Contraceptive Risks
[5] DrugPatentWatch - Annovera