Apatinib, a commonly used tyrosine kinase inhibitor in cancer treatment, can cause adverse reactions such as hypertension. Hypertension, in turn, can increase the risk of certain cancers. The coexistence of these diseases makes the use of combination drugs more common in clinical practice, but the potential interactions and regulatory mechanisms in these drug combinations are poorly understood. We used the humanized CYP2D6 mouse model to predict the effect of apatinib on the pharmacokinetics and pharmacodynamics of metoprolol and investigated the interactional mechanism. The inhibitory effects and mechanisms of apatinib on metoprolol were investigated in vitro by using wild-type mouse liver microsomes (WT MLMs), humanized CYP2D6 mouse liver microsomes (hCYP2D6 MLMs), and human liver microsomes (HLMs). Molecular docking was utilized to explore the structural basis of the observed inhibitory mode. And in vivo interaction between apatinib and metoprolol was assessed by pharmacokinetics study using the humanized CYP2D6 mice. In vitro studies and molecular docking experiments indicated that apatinib competitively inhibited the metabolism of metoprolol. In vivo findings revealed that the administration of apatinib combined with metoprolol resulted in a significant increase in the AUC(0-t), AUC(0-∞) and Cmax of metoprolol; additionally, there was a reduction in the CLz/F and heart rate, indicating that apatinib strongly inhibited metoprolol metabolism. And the homologous CYP2D6 protein in WT mice was more sensitive to apatinib compared to the hCYP2D6 mice. Gender analysis revealed that metoprolol accumulation was more pronounced in male mice when combined with apatinib, indicating a higher susceptibility to cardiotoxicity in males.