Year: 2026
Type: article
Abstract: Research objective: The objective of this study was to analyze and compare the effects of levonorgestrel (LNG) and ulipristal acetate (UPA), used in emergency contraception, on the female hormonal cycle, with particular emphasis on ovulation timing, hormonal regulation (LH, FSH, estradiol, progesterone), menstrual cycle alterations, and endometrial effects. Methodology: The study is based on a narrative review of peer-reviewed clinical and experimental literature addressing the pharmacological mechanisms, pharmacokinetics, pharmacodynamics, clinical efficacy, and safety of LNG and UPA. Data from randomized trials, observational studies, and regulatory reports were analyzed to assess short- and long-term hormonal effects and clinical outcomes associated with emergency contraceptive use. Main conclusions: Both levonorgestrel and ulipristal acetate are effective and safe agents for emergency contraception, acting primarily through inhibition or delay of ovulation rather than interference with implantation. LNG is effective mainly when administered before the luteinizing hormone surge, whereas UPA can inhibit ovulation even after LH elevation, providing a longer therapeutic window. Observed hormonal and menstrual changes are temporary and reversible, with no evidence of long-term endocrine disruption or negative impact on fertility. Application of the study: The findings support evidence-based clinical decision-making in emergency contraception by facilitating appropriate drug selection depending on cycle phase, timing after intercourse, and individual patient factors. The study also contributes to patient counseling, safety assurance, and the reduction of misconceptions regarding the mechanism of action of emergency contraceptives. Originality/Novelty of the study: This study offers an integrated comparative overview of LNG and UPA by combining hormonal, clinical, and pharmacokinetic perspectives, highlighting their differential effects on the female hormonal cycle. By synthesizing current evidence, it addresses existing misconceptions and emphasizes the non-abortifacient nature of emergency contraception, contributing to both clinical practice and public health education.
Field: Medicine
Domain: Health Sciences
Open Access status: diamond
OpenAlex ID: W7133134582