The Hemostatic Defect Produced by Carbenicillin

Blood coagulation and platelet function were examined in 17 human volunteers receiving doses of 300, 400 or 600 mg/kg/day of carbenicillin. Platelet function was also investigated in 5 patients receiving carbenicillin for the treatment of gram negative infection. In volunteers, plasma coagulation remained normal. However, defective platelet function was seen in all volunteers and patients. Eleven of 11 volunteers demonstrated abnormal adenosine diphosphate induced platelet aggregation; 6 of 11 demonstrated abnormal l epinephrine induced aggregation, and 5 of 11 abnormal collagen induced aggregation; in 14 of 20 studies, there was prolongation of bleeding time; 7 of 11 volunteers had reduced clot retraction; 8 of 11 had decreased prothrombin consumption. Prolongation of bleeding time and defective clot retraction appeared to be dose dependent. Three volunteers given 600 mg/kg/day and 2 patients given 340 and 375 mg/kg/day, respectively, experienced bleeding while receiving carbenicillin. The mechanism of platelet inhibition by carbenicillin is unknown. (17 references.)