Answer: B
Abciximab, eptifibatide and tirofiban are only available in iv form. Trials on orally administered GP IIb/IIIa antagonists have failed to demonstrate any benefit, and even indicated significantly increased mortality in ACS cases.
PAR antagonists are available in oral forms, but are under research.
1. P., Huang Z., Held C., et al.Thrombin-Receptor Antagonist Vorapaxar in Acute Coronary Syndromes. N Engl J Med 2012; 366:20-33. January 5, 2012: In this trial, vorapaxar, a protease-activated–receptor 1 antagonist that inhibits thrombin-induced platelet activation, was not effective in reducing the primary cardiovascular efficacy end point, and it increased rates of bleeding, including serious bleeding and intracranial hemorrhage.
2. Morrow D.A., Braunwald E., Bonaca M.P., et al.Vorapaxar in the Secondary Prevention of Atherothrombotic Events. N Engl J Med 2012; 366:1404-1413. April 12, 2012: Patients with atherosclerotic vascular disease were randomly assigned to receive the thrombin antagonist vorapaxar or placebo. Vorapaxar reduced the rate of subsequent cardiovascular death, myocardial infarction, or stroke but increased the rate of moderate or severe bleeding.
Reference
Xuebin Ji and Ming Hou. Review: Novel agents for anti-platelet therapy. Journal of Hematology & Oncology 2011, 4:44 (Open Access here)