Formulation and Pharmacokinetics of Immediate-Release Oral Contraceptives

Review Article

Abstract

Immediate-release oral contraceptives are of vital importance in modern reversible contraception. These formulations, primarily categorized as combined oral contraceptives (COCs) containing both an estrogen and a progestin, or progestin-only pills (POPs), are engineered for rapid disintegration and subsequent drug absorption. The therapeutic efficacy of these agents is critically dependent on achieving and maintaining plasma hormone concentrations sufficient to inhibit ovulation and induce changes in cervical mucus and the endometrium. This is achieved through clever formulation design, where the selection of pharmaceutical excipients is paramount. Binders, diluents, and lubricants ensure tablet integrity and manufacturability, while solubilizing agents are often required to improve the dissolution of poorly water-soluble hormones like ethinylestradiol and various progestins. The inclusion of superdisintegrants, such as croscarmellose sodium and sodium starch glycolate, is a key strategy to accelerate tablet breakup, thereby facilitating prompt drug release. While offering the benefits of a rapid onset of action and ease of manufacturing, immediate-release dosage forms present significant clinical challenges. The characteristic rapid absorption and elimination profile results in substantial fluctuations in plasma hormone levels, creating a narrow window for dosing. This pharmacokinetic profile makes the therapy highly unforgiving of missed or delayed doses, which remains a primary contributor to contraceptive failure in typical use. This review discusses about the formulation of these essential medicines and compares the advantages and limitations that define their clinical application