As with other plasma preparations, reactions manifested by chills and fever may occasionally be seen, particularly when large doses of PROPLEX T (factor ix complex) , Factor IX Complex, Heat Treated are administered.17,18 A rate of infusion that is too rapid may cause headache, flushing, and changes in pulse rate and blood pressure. In such instances, stopping the infusion allows the symptoms to disappear promptly. With all but the most reactive individuals, the infusion may be resumed at a slower rate. (See Rate of Administration.) The risk of thrombosis is present with the administration of PROPLEX T (factor ix complex) , Factor IX Complex, Heat Treated.