Abstract: AimTo establish a sensitive and specific method to simultaneous determination of pseudoephedrine and chlorpheniramine in human plasma. MethodsPseudoephedrine and chlorpheniramine were extracted from alkaline plasma with T-butyl methyl ether as the base form, and were back-extracted into 1.5% hydrochloride solution. The two drugs were simultaneous determined by RP-HPLC with ultraviolet detection at 200 nm, using dextromethorphan as internal standard. A C₁₈ column (250 mm×46 mm ID) and a mobile phase containing acetonitrile-water-triethylamine (46∶54∶0.2, containing 10 mmol·L_-1 sodium dodecyl sulfate (SDS) and 60 mmol·L_-1 NaH₂PO₄, adjusted pH to 2.6 with H₃PO₄) were used. ResultsThe limit of quantification was 10.0 and 0.5 μg·L_-1, the linear range was 1.5-0.01 mg·L_-1 and 75-0.5 μg·L_-1, for pseudoephedrine and chlorpheniramine, respectively. The within-day and between-day RSD were less than 12.4%, and the average recovery was between 97.3%-109.4%. ConclusionThe method was sensitive, specific, simple, and suitable for drug level monitoring in clinical pharmacokinetic study.