Most of the drug circulates bound to platelets. A transfusion of platelets will reverse the effect by allowing the drug to redistribute among all the platelets, thereby reducing the level of platelet inhibition. Thus, the level of platelet inhibition is directly related to the drug level in the blood. 5 pro-drugs, which are absorbed and then converted to active compounds in the blood.
Variability is probably the biggest issue with the oral agents.
It is hoped that the Class I agents, with tight binding to the receptor and long half-lives similar to abciximab, can overcome this prothrombotic issue. Indeed, experimental data with one such agent, roxifiban, has shown no prothrombotic effects, and improved antithrombotic efficacy compared with the Class II agents such as orbofiban. N Engl J Med . Kereiakes DJ, Kleiman NS, Ambrose J, et al. J Am Coll Cardiol .