This is meant as a brief revision antiplatelet drug pharmacology. Antiplatelet agents have come up as a part of a question on oral anticogulation of AF (Question 4 from the first paper of 2015), alongside with novel oral anticoagulants.Similarly, Question 13.2 from the first paper of 2009 asked the candidates to "briefly outline the mode of action and half life of aspirin, tirofiban and clopidogrel".  In order to simplify revision, the following table has been constructed.

 

Drug

Chemical properties

Mechanism

Clearance

Half-life

Duration of effect

Aspirin

Salycilate;
Weak acid

Irreversible COX-1 inhibition, thus decreased production of the prothrombotic thromboxane A2

Renal

1-2 hrs

 

7-10 days

Clopidogrel

Thienopyridine

Irreversible inhibition of P2Y12 ADP receptor, thus inhibition of  cAMP-dependent platelet activation

50% renal,
50% biliary

0.5-1 hrs

7-10 days

Prasugrel

Thienopyridine

Irreversible inhibition of P2Y12 ADP receptor, thus inhibition of  cAMP-dependent platelet activation

Renal

7 hrs

7-10 days

Ticagrelor

Nucleoside (adenosine) analogue

Reversible inhibition of P2Y12 ADP receptor, thus inhibition of  cAMP-dependent platelet activation

Biliary

7-8 hrs

3-5 days

Abciximab

Fab fragment of a human monoclonal antibody

Glycoprotein IIb/IIIa inhibition, thus inhibition of platelet binding to fibrinogen and von Willebrand factor.

Reticulo-endothelial system

0.5 hr

18-24 hours

Tirofiban

Small molecule non-peptide

Glycoprotein IIb/IIIa inhibition, thus inhibition of platelet binding to fibrinogen and von Willebrand factor.

Renal

2 hrs

4-8 hours

 

 

 

 

References

Siller‐Matula, Jolanta M., Julia Krumphuber, and Bernd Jilma. "Pharmacokinetic, pharmacodynamic and clinical profile of novel antiplatelet drugs targeting vascular diseases." British journal of pharmacology 159.3 (2010): 502-517.

 

Farid, Nagy A., Atsushi Kurihara, and Steven A. Wrighton. "Metabolism and disposition of the thienopyridine antiplatelet drugs ticlopidine, clopidogrel, and prasugrel in humans." The Journal of Clinical Pharmacology 50.2 (2010): 126-142.

 

Levine, Glenn N., et al. "Newer pharmacotherapy in patients undergoing percutaneous coronary interventions: a guide for pharmacists and other health care professionals." Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy 26.11 (2006): 1537-1556.