Levonorgestrel in Emergency Contraception: Pharmacology, Mechanism of Action and Clinical Implications: A Review

Contraception plays an important role in reproductive health by preventing unintended pregnancies and enabling effective family planning. Among the various hormonal contraceptives developed over the years, levonorgestrel (LNG) has emerged as one of the most widely used and effective agents. Levonorgestrel is a second-generation synthetic progestin derived from 19-nortestosterone and has been extensively used in oral contraceptive pills, emergency contraceptives, intrauterine systems, and implantable devices. The present review aims to summarize the historical development of contraceptive methods with special emphasis on the discovery, uses, mechanism of action, and possible adverse effects of levonorgestrel. Information for this review was collected from secondary sources including scientific journals, books, and electronic databases such as Google Scholar and PubMed. Available literature indicates that levonorgestrel primarily acts by inhibiting or delaying ovulation, suppressing the luteinizing hormone surge, increasing the viscosity of cervical mucus, and inducing changes in the endometrium that reduce the probability of fertilization and implantation. Although levonorgestrel is considered safe and highly effective, certain side effects such as menstrual irregularities, nausea, headache, and endometrial changes have been reported. Overall, levonorgestrel remains an important and reliable contraceptive agent with significant contributions to modern reproductive health care. Continued research is necessary to further understand its long-term effects and to improve contraceptive strategies for better safety and effectiveness.