WEN-JEN LINChen R.R.-L.Suen S.-L.2021-01-072021-01-07199610161015https://www.scopus.com/inward/record.uri?eid=2-s2.0-0029989023&partnerID=40&md5=66343469e2330eb4107fd91666eb61f9https://scholars.lib.ntu.edu.tw/handle/123456789/539794An HPLC analytical method was developed to quantify benzonatate and its metabolite, 4-(butylamino)benzoic acid, in plasma. The detection limits concentrations for benzonatate and 4-(butylamino)benzoic acid were 0.2 and 0.02 μg/mL, respectively. The analytical method for 4-(butylamino)benzoic acid was further validated. Both intra- and interday mean values were within ± 8 % of the actual values. A preliminary pharmacokinetic study of 4- (butylamino)benzoic acid in healthy male volunteers was performed. 4- (Butylamino)benzoic acid was stable in plasma at a detectable low concentration that was directly related to its therapeutic effect. Measurement of the concentration of 4-(butylamino)benzoic acid rather than benzonatate may be useful for the evaluation of the bioequivalence of benzonatate when the concentration of benzonatate in plasma is too low to be detected.4-(Butylamino)benzoic acid; Benzonatate; HPLC; Pharmacokinetics[SDGs]SDG3benzoic acid derivative; benzonatate; drug metabolite; adult; analytic method; article; coughing; drug blood level; drug determination; drug effect; gas chromatography; human; human experiment; male; mass spectrometry; normal human; respiratory tract disease; reversed phase high performance liquid chromatographyjournal article2-s2.0-0029989023