Ulipristal acetate, sold under the brand name Ella among others, is a medication used for emergency contraception and uterine fibroids. As emergency contraception it should be used within 120 hours of vaginally penetrating intercourse. For fibroids it may be administered as a repeated low daily oral dose to reduce uterine bleeding and shrink leiomyoma volume prior to surgery or to control symptoms during intermittent treatment; the compound is a selective progesterone receptor modulator with dose-dependent antagonistic and partial agonistic effects at progesterone receptors in the ovary and endometrium, which delays or inhibits follicular rupture, induces amenorrhea, reduces fibroid cell proliferation and extracellular matrix deposition, and alters endometrial receptivity. In emergency use the recommended single oral dose is 30 mg; for fibroid management typical clinical regimens have used 5 mg once daily in defined treatment courses with liver function monitoring due to rare reports of hepatic injury. Pharmacokinetics: orally absorbed with peak plasma concentrations in 1 to 3 hours, extensive hepatic metabolism (primarily CYP3A4) to pharmacologically active and inactive metabolites, high plasma protein binding, and an elimination half-life that supports single-dose emergency use and daily dosing regimens for chronic indications.
Parent: Ulipristal Acetate
Parent: Ulipristal Acetate
Related substances and impurities for ulipristal acetate include the deacetylated parent compound (ulipristal), N-desalkyl variants, hydroxylated metabolites, epimerization or stereoisomeric impurities, and minor oxidative or dealkylation products formed during synthesis or storage; routine analytical control uses validated HPLC-UV/LC-MS methods and, where relevant, chiral HPLC to resolve stereoisomers. Typical pharmaceutical quality limits applied by manufacturers and regulators are: individual identified related substances generally not exceeding 0.5% w/w, unspecified impurities limited to 0.1% w/w or lower depending on qualification, and total impurities commonly controlled to 1.5 to 2.0% w/w in the API or finished product; any potential genotoxic impurity must be evaluated and controlled in accordance with ICH M7 guidance with limits set relative to the acceptable intake for the clinical daily dose. Specification controls also include limits for residual solvents, heavy metals, and water content, and stability studies to monitor impurity profile over shelf life.
Ulipristal acetate is a selective progesterone receptor modulator that acts as a receptor antagonist in ovarian follicles and at the endometrium. For emergency contraception it primarily delays or inhibits follicular rupture, thereby preventing or postponing ovulation; it also causes endometrial changes that reduce the likelihood of implantation. In uterine fibroids it modulates progesterone signaling in leiomyoma tissue to reduce cellular proliferation, induce apoptosis, decrease extracellular matrix production, and reduce uterine blood loss, leading to reduced bleeding and fibroid volume during treatment.
Some regulatory authorities, including certain national agencies, have restricted or suspended marketing authorizations for ulipristal acetate in the uterine fibroid indication after rare reports of serious drug-induced liver injury and subsequent safety reviews by international regulators. Decisions described as bans in some jurisdictions reflect precautionary regulatory measures to protect patients and to require additional safety monitoring or risk minimization; the regulatory status can differ between the emergency contraception indication and the fibroid indication, so clinicians and patients should consult the current local regulatory guidance for availability and permitted uses.
Plan B contains levonorgestrel 1.5 mg as a progestin-only emergency contraceptive and is most effective when taken within 72 hours of unprotected intercourse, acting mainly by preventing or delaying ovulation and by impairing sperm function. Ella contains ulipristal acetate 30 mg, is effective up to 120 hours after intercourse, and is a selective progesterone receptor modulator that can delay ovulation even when the luteinizing hormone surge has started; Ella typically requires a prescription in many countries and has different drug interaction considerations, notably reduced efficacy with strong CYP3A4 inducers.
Ulipristal acetate is used as a single-dose oral emergency contraceptive taken within 120 hours of unprotected intercourse and as a medical treatment for symptomatic uterine fibroids to control bleeding and reduce fibroid size in defined treatment courses. Clinical use for fibroids has included 5 mg once-daily regimens for limited treatment periods with monitoring of liver function because of rare hepatic safety concerns; treatment decisions should follow current regulatory labeling and clinician guidance.
