Tadalafil and Sildenafil illicit association: Stability- indicating HPLC method, photodegradation kinetic and toxicological studies

Abstract The illicit market of counterfeit medicines containing sildenafil and tadalafil has been causing serious public health problems. Thus, further studies on this illicit association are needed. A stability-indicating HPLC method was developed for simultaneous determination of tadalafil (TAD) and sildenafil (SIL) using a C18 column (250 x 4.6 mm, 5 µm). Detection was achieved at 284 nm, for TAD, and 292 nm, for SIL. The method was considered to be specific, linear, precise, accurate, robust, and sensitive. In the photodegradation kinetic studies, the drugs showed a first-order reaction rate when isolated, and zero-order when associated. Toxicological assays demonstrated that the photodegraded drugs decreased cell viability in compared to non- degraded drugs, suggesting cytotoxic activity. Additional, mutagenic activity was not observed under the tested conditions. Photodegraded drugs, in association, depicted DNA damage index, suggesting genotoxic effects. The obtained results will be able to support the forensic intelligence laboratories, as well as to alert the population about the risk inherent to consuming counterfeit products.

摘要 含有西地那非（sildenafil）与他达拉非（tadalafil）的假冒药品非法流通市场已引发严峻的公共卫生问题，因此针对这类非法联用药物的深入研究仍具必要性。本研究开发了一种稳定性指示型高效液相色谱（High Performance Liquid Chromatography，HPLC）法，可同时测定他达拉非（tadalafil，TAD）与西地那非（sildenafil，SIL），采用规格为250×4.6 mm、5 µm的C18色谱柱。检测波长分别设定为他达拉非284 nm、西地那非292 nm。该方法经验证具备专属性、线性、精密度、准确度、耐用性与灵敏度。光降解动力学研究结果显示，单一存在的两种药物均遵循一级反应动力学规律，而二者联用时则表现为零级反应。毒理学实验表明，与未降解的药物相比，光降解药物可降低细胞存活率，提示其具有细胞毒性活性。此外，在本次实验所设置的条件下未观察到诱变活性。联用状态下的光降解药物可检测到DNA损伤指数，提示其存在遗传毒性效应。本研究所得结果可为法医情报实验室提供技术支撑，同时也可用于警示公众认清食用假冒药品所潜藏的固有风险。