作者:Lian Zhou、Sanjeev Kaul、Peggy Liu-Kreyche、Scott B. Tran、Robert R. Espina、Bethanne M. Warrack、Vikram A. Roongta、Ramaswamy A. Iyer
DOI:10.1124/dmd.109.030239
日期:2010.4
The disposition of stavudine, a potent and orally active nucleoside reverse transcriptase inhibitor, was investigated in six healthy human subjects. Before dosing humans with [1′-14C]stavudine, a tissue distribution study was performed in Long-Evans rats. Results from this study showed no accumulation of radioactivity in any of the tissues studied, indicating that the position of the 14C-label on the molecule was appropriate for the human study. After a single 80-mg (100 μCi) oral dose of [1′-14C]stavudine, approximately 95% of the radioactive dose was excreted in urine with an elimination half-life of 2.35 h. Fecal excretion was limited, accounting for only 3% of the dose. Unchanged stavudine was the major drug-related component in plasma (61% of area under the plasma concentration-time curve from time zero extrapolated to infinite time of the total plasma radioactivity) and urine (67% of dose). The remaining radioactivity was associated with minor metabolites, including mono- and bis-oxidized stavudine, glucuronide conjugates of stavudine and its oxidized metabolite, and an N -acetylcysteine (NAC) conjugate of the ribose (M4) after glycosidic cleavage. Formation of metabolite M4 was shown in human liver microsomes incubated with 2′,3′-didehydrodideoxyribose, the sugar base of stavudine, in the presence of NAC. In addition, after similar microsomal incubations fortified with GSH, two GSH conjugates, 3′-GS-deoxyribose and 1′-keto-2′,3′-dideoxy-3′-GS-ribose, were observed. This suggests that 2′,3′-didehydrodideoxyribose underwent cytochrome P450-mediated oxidation leading to an epoxide intermediate, 2′,3′-ribose epoxide, followed by GSH addition. In conclusion, absorption and elimination of stavudine were rapid and complete after oral dosing, with urinary excretion of unchanged drug as the predominant route of elimination in humans.
对强效口服生物活性核苷酸逆转录酶抑制剂斯他夫定(stavudine)的处置进行了研究,参与者为六名健康人类受试者。在对人类进行[1′-14C]斯他夫定给药之前,首先在长伊凡斯大鼠中进行了组织分布研究。该研究结果显示,在所研究的任何组织中均未发现放射活性积累,这表明分子上14C标记的位置适合人类研究。单次口服80毫克(100 μCi)[1′-14C]斯他夫定后,约95%的放射性剂量通过尿液排泄,消除半衰期为2.35小时。粪便排泄有限,仅占剂量的3%。未改变的斯他夫定是血浆中主要的药物相关成分(从零时到无限时间的血浆浓度-时间曲线下面积中占61%的总血浆放射性)和尿液(占67%的剂量)。剩余的放射活性与少量代谢物相关,包括单氧化和双氧化的斯他夫定、斯他夫定及其氧化代谢物的葡萄糖苷酸结合物,以及在糖苷键切割后形成的核糖的N-乙酰半胱氨酸(NAC)结合物(M4)。在与NAC共同孵育的2′,3′-二脱氧核糖的人的肝脏微粒体中显示了代谢物M4的形成。此外,在类似的微粒体孵育中,补充了GSH,观察到了两个GSH结合物,分别为3′-GS-脱氧核糖和1′-酮-2′,3′-二脱氧-3′-GS-核糖。这表明2′,3′-二脱氧核糖经历了细胞色素P450介导的氧化反应,导致环氧中间体2′,3′-核糖环氧化物的形成,随后发生了GSH的加入。总之,斯他夫定的吸收和消除在口服给药后迅速而彻底,尿液中未改变的药物排泄是人类中主要的消除途径。