From the Guidelines
Levonorgestrel does not significantly affect platelet aggregation or aggregometry test results. Levonorgestrel is a progestin hormone used in various contraceptive methods, including hormonal IUDs, and has minimal impact on hemostasis parameters 1. Unlike estrogen-containing contraceptives, which can increase clotting factors and potentially affect platelet function, levonorgestrel-only contraceptives do not increase the risk of venous thromboembolism (VTE) in healthy women, with relative risks (RRs) of 0.90 (95% confidence interval [95% CI] 0.57–1.45) and 0.61 (95% CI 0.24–1.53) for the progestin-only pill and progestin IUD, respectively 1.
Key Points
- Levonorgestrel-only contraceptives, such as the Mirena IUD, do not need to be discontinued before platelet function testing 1.
- The progestin-only pill is also a low-risk alternative for patients who are unable or unwilling to use an IUD, with minimal impact on hemostasis parameters 1.
- Combined hormonal contraceptives, which contain both levonorgestrel and ethinyl estradiol, may influence platelet function and coagulation, and should be considered when interpreting aggregometry results 1.
- The risk of VTE in healthy women taking combined estrogen-progestin contraceptives is 36 times higher than the baseline annual risk, whereas progestin-only methods are widely accepted as a lower-risk option in patients for whom estrogens are contraindicated 1.
Clinical Implications
- Patients taking levonorgestrel-only contraceptives can generally undergo platelet aggregometry testing without discontinuing their medication, as it should not interfere with test interpretation 1.
- Clinicians should consider the type of contraceptive method used by patients when interpreting aggregometry results, and take into account the potential effects of estrogen-containing contraceptives on platelet function and coagulation 1.
From the Research
Levonorgestrel and Aggregometry
- The studies provided do not directly address the topic of levonorgestrel and aggregometry, but rather focus on the safety and risks associated with levonorgestrel and other hormonal contraceptives in relation to venous thrombosis and coagulopathy 2, 3, 4, 5, 6.
- However, one study compared the haemostatic effects of a new combined oral contraceptive, nomegestrol acetate/17β-estradiol, with those of levonorgestrel/ethinyl estradiol, and found that the former had fewer adverse effects on blood coagulation and fibrinolysis markers 6.
- Another study found that levonorgestrel intrauterine devices did not increase the risk of venous thrombosis, whereas other hormonal contraceptives, such as combined oral contraceptives and vaginal rings, did increase this risk 4.
- The use of levonorgestrel as an emergency contraceptive did not result in a higher risk of venous thromboembolism, according to one study 5.
- Overall, the evidence suggests that levonorgestrel may have a more favorable safety profile compared to other hormonal contraceptives, particularly in terms of venous thrombosis risk, but more research is needed to fully understand its effects on aggregometry and coagulation.
Key Findings
- Levonorgestrel intrauterine devices do not increase the risk of venous thrombosis 4.
- Levonorgestrel emergency contraceptives do not result in a higher risk of venous thromboembolism 5.
- The haemostatic effects of levonorgestrel/ethinyl estradiol are less favorable compared to nomegestrol acetate/17β-estradiol 6.
- Combined oral contraceptives with levonorgestrel have a lower risk of venous thrombosis compared to those with other progestogens, such as desogestrel and drospirenone 3, 5.