Abstract: OBJECTIVE  To prepare piperine-theanine co-amorphous complex (PIP-THE CAC) and improve dissolution and bioavailability of PIP.METHODS  The PIP-THE CAC was prepared by quench cooling, characterized by DSC, XRPD, FTIR, SEM and evaluated by in vitro dissolution under sink and non-sink conditions. The physical stability of PIP-THE CAC was also investigated. Besides, the bioavailability study of PIP-THE CAC was conducted by pharmacokinetic tests in rats.RESULTS  DSC and XRPD indicated that PIP-THE CAC was successfully prepared. FTIR confirmed that there was intermolecular hydrogen bond interaction between PIP and THE in the prepared CAC, resulting in excellent physical stability. SEM showed that the CAC was irregular, lumpy and granular, and the characteristics of PIP and THE were disappeared. Besides, compared with pure PIP and PIP-THE physical mixture, PIP-THE CAC possessed a higher dissolution rate and a higher dissolution degree, and maintained supersaturated degree for long time in vitro dissolution experiments. Pharmacokinetic results showed that C_max, t_max, AUC_{0-24 h} and AUC_0-∞ of PIP-THE CAC group increased significantly (P < 0.01) compared with raw PIP, and the C_max and bioavailability of PIP increased by 2.03 and 1.93 times, respectively (P < 0.01).CONCLUSION  PIP-THE CAC prepared by THE co-amorphization with PIP can effectively improve the solubility/dissolution and oral bioavailability of PIP.