activated protein c–protein c inhibitor activated protein c–protein c inhibitor activated protein c–protein c inhibitor (apc-pci) is a complex of activated protein c (apc) and protein c inhibitor (pci). it has been measured in coagulation testing to evaluate coagulation, thrombosis, and other cardiovascular complications. it is a marker of thrombin generation and indicates hypercoagulability. the half-life of apc-pci is either 40 minutes or 140 minutes. ethinylestradiol-containing birth control pills have been found to increase levels of apc-pci to a similar degree as thrombin–antithrombin complex (tat) and to a greater extent than d-dimer. however, only apc-pci was able to differentiate between a second- and third-generation birth control pill. another complex related to apc-pci is the activated protein c–α1-antitrypsin (apcat) complex.