Shuanghuanglian oral liquid is a common traditional Chinese medicine used to treat respiratory tract infections. Its major components are baicalin, chlorogenic acid, and forsythin. In this study, the main drug‐related components in human plasma after oral administration of Shuanghuanglian were initially identified using ultra‐performance liquid chromatography‐ultraviolet detector/quadrupole time‐of‐flight mass spectrometry. Thirteen components from baicalin were identified, including the parent drug baicalin and aglycone baicalein. Only one metabolite related to chlorogenic acid, a sulfate conjugate formed after hydrolysis, and one metabolite related to forsythin, a sulfate conjugate of forsythin aglycone, were detected. Subsequently, a liquid chromatography‐tandem mass spectrometry method was established and validated to simultaneously determine baicalin and baicalein, the primary active components. After simple protein precipitation, the analytes were separated on a BEH C18 column using a 5 min‐gradient elution to avoid interference from baicalin isomers and their in‐source dissociation. Excellent linearity was observed over the concentration ranges of 5.00–2000 ng/ml for baicalin and 1.00–100 ng/ml for baicalein. The validated method was successfully applied to a pharmacokinetic study of an oral administration of 60 ml Shuanghuanglian in healthy subjects. This study provided a foundation to investigate the clinical efficacy and safety of Shuanghuanglian further.

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