Background: Abciximab reduces the thrombotic complications of angioplasty. It is also used, as a 'bail out' treatment when angioplasty is complicated by thrombus but its speed of action is not known. This study sought to establish how quickly abciximab blocks the aggregation of both quiescent and activated platelets to explain this rapid efficacy.
Methods: Optical aggregometry (OA) and whole blood electrical impedance platelet aggregometry (WBEA) were performed with blood from 10 healthy volunteers. Abciximab 5 microg/ml was added in each case with saline control 5 minutes before agonist, 10 seconds before agonist and during aggregation.
Results: (1) Abciximab administered 5 minutes before agonist, completely inhibited aggregation with OA: (medians and ranges) 0% (all 0), control: 71% (50-95%) p < 0.001. and with WBEA: 0 omega (all 0 omega), control: 7.5 omega (4.8-12.5 omega) p = 0.016. (2) When administered 10 s before agonist with OA a small initial degree of aggregation occurred but this was rapidly reversed (time to reversal: 2 mins (1-4.5 mins) to low levels of aggregation 16.5% (0-22%), control 72.5% (55-95%) p = 0.002. With WBEA aggregation was completely inhibited: 0 omega (all 0 omega), control: 7.5 omega (4.8-12.3 omega) p = 0.016. (3) When administered during aggregation, with OA the rise in the aggregometry tracing was rapidly arrested (time to arrest: 1.5 mins (0.1-3 mins)) with no further aggregation occurring: 42% (30-57%), control: 80% (60-100%) p = 0.002. With WBEA the findings were similar: (time to arrest 1.5 mins (1-2 mins)) 6.3 omega (1.5-11.3 omega), control: 10 omega (3-12 omega) p = 0.031.
Conclusions: These data suggest that when administered during a procedure in which thrombus has occurred, aggregation may be rapidly arrested. This applies to quiescent platelets but also activated platelets undergoing aggregation.