A solid phase microextraction (SPME) method followed by LC-MS/MS analysis was developed to determine the concentration of tranexamic acid (TA) in plasma. The use of a new biocompatible C18 coating allowed the direct extraction from complex biological samples without prior sample preparation; no matrix effect was observed. The results revealed that SPME was suitable for the analysis of polar drugs such as TA; such an application was previously inaccessible because of the limited availability of SPME coatings that can extract polar molecules. The proposed method was validated according to the bioanalytical method validation guidelines. LOD and LLOQ were 0.5 and 1.5 μg/ml, respectively. The recovery for the method was 0.19%, and the accuracy and precision of the method were <9 and <11%, respectively, with the exception of LLOQ, where the values were <16 and <13%, respectively. The performance of the proposed method was also compared against that of the standard techniques of protein precipitation and ultrafiltration. A statistical analysis indicated a clinically significant agreement among all assays. Another advantage of SPME over conventional techniques was the easy automation and feasibility of in vivo analysis; this advantage makes it possible to use the proposed method for an on-site analysis in clinical practice.
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