Update of safety profile of levonorgestrel: a disproportionality analysis based on FAERS from 2004 to 2023

Levonorgestrel has been utilized in emergency contraception (EC) and for endometrial conditions. While abnormal uterine bleeding is a recognized adverse event (AE), other potential AEs remain undocumented. Safety data for levonorgestrel were acquired from the United States FDA Adverse Event Reporting System (FAERS) database, covering the period from the first quarter (Q1) of 2004 to the fourth quarter (Q4) of 2023. A disproportionality analysis was conducted to assess the association between levonorgestrel and AEs. A total of 136,168 AEs associated with levonorgestrel were reported. 106 preferred terms (PTs) and 2 system organ class (SOCs) met the criteria established by four algorithms. The identified PTs were vaginal hemorrhage, irregular menstruation, genital hemorrhage and so on. The SOCs encompassed reproductive system and breast disorders, as well as pregnancy, puerperium, and perinatal conditions. Although most findings align with the existing drug inserts for levonorgestrel, several novel AEs were identified in our study. Therefore, ongoing monitoring of this drug is essential and its safety profile should be updated regularly to enhance clinical practice regulation.