Levonorgestrel (LNG) is a synthetic progestin that is available in oral contraceptive tablets, a subdermal implant, and an intrauterine system for contraception. LNG pharmacokinetics are a pivotal determinant of contraceptive efficacy and essential in assessing drug-drug interactions influencing LNG exposure following different routes of LNG administration. A highly sensitive LC-MS/MS method was developed and validated to quantify levonorgestrel in human plasma. Liquid-liquid extraction was utilized with a sample volume of 500 μL to extract levonorgestrel from plasma. Chromatographic separation of LNG was achieved with a Fortis™ C18 (3 μm: 100 mm × 2.1 mm) reverse phase analytical column. The mobile phases consisted of de-ionized water plus 0.1% NH₄OH (100:0.1%, v/v) (A), and methanol plus 0.1% NH₄OH (100:0.1%, v/v) (B) delivered as a gradient at a flow rate of 400 μL/min. Detection of LNG and internal standard (D-(−)-norgestrel-d7) was achieved using positive polarity mode monitoring at 313.2–245.2 amu and 320.1–251.2 amu, respectively. The assay was linear over the calibration range of 49.6 to 1500 pg/mL. This method was used to quantify plasma LNG released by subdermal implant in support of a drug interaction study among women with HIV receiving efavirenz- or nevirapine-based antiretroviral therapy.

左炔诺孕酮（LNG）是一种合成的孕激素，可用于口服避孕药，皮下植入物和子宫内避孕系统。LNG药代动力学是避孕药效的关键决定因素，在评估不同LNG施用途径下影响LNG暴露的药物相互作用时必不可少。开发并验证了一种高灵敏度的LC-MS / MS方法，可定量测定人血浆中的左炔诺孕酮。利用液-液萃取，样品体积为500μL，从血浆中萃取左炔诺孕酮。LNG的色谱分离是通过Fortis™C18（3μm：100 mm×2.1 mm）反相分析柱实现的。流动相由去离子水加0.1％NH ₄ OH（100：0.1％，v / v）（A）和甲醇加0.1％NH组成以400μL/ min的流速以梯度形式输送₄ OH（100：0.1％，v / v）（B）。使用正极性模式监测分别在313.2–245.2 amu和320.1–251.2 amu上实现了LNG和内标（D-（-）-norgestrel-d7）的检测。该测定在49.6至1500 pg / mL的校准范围内呈线性。该方法用于量化皮下植入物释放的血浆LNG，以支持接受依非韦伦或奈韦拉平为基础的抗逆转录病毒疗法治疗的HIV感染妇女的药物相互作用研究。