Effect of intravenous carbenicillin, cefoxitin and cefamandole on ADP-induced platelet aggregation and shape change

The effect of a large daily dose of i.v. carbenicillin, cefoxitin and cefamandole on platelet aggregation with adenosine diphosphate (ADP) and the effect of carbenicillin on ADP induced shape change were evaluated. Six volunteers received carbenicillin 100 mg/kg every 4 hours. Three of them also received cefoxitin 3 gm every 6 hours and cefamandole 2 gm every 4 hours. All treatments were separated by 14 days. Prior to treatment, as well as 1 and 24 hours after the last dose of antibiotic, citrated platelet-rich plasma was tested for the extent of aggregation at a series of ADP concentrations. As previously reported by several groups, carbenicillin decreased the sensitivity of platelets in their aggregation response to ADP. Thus, the concentration of ADP needed to obtain 50% of maximal aggregation response was increased 3.5±1.7 (S.D.) fold. In addition, when measured separately, the sensitivity of platelets in their shape change response to ADP was decreased to a similar degree. The concentration of ADP needed to produce 50% of maximal shape change response was 2.8±1.6 (S.D.) fold higher after carbenicillin treatment. The results are in accordance with previous in vitro studies suggesting that carbenicillin interferes with the initial phase of platelet activation. Cefoxitin and cefamandole had no apparent effect on platelet aggregation.