Antiplatelets Flashcards
What are antiplatelet drug uses
- since arterial clots are primarily made up of a platelet core, antiplatelet agents are primarily used to prevent arterial clots
Which of the antiplatelet drugs have similar function
1) aspirin (cox inhibitor), P2Y12 inhibitors, and other miscellaneous antiplatelets drugs affect only one pathway in platelet activation
2) GP IIb/IIIa inhibitors block the final common step in platelet activation and thus are much more potent antiplatelets
Aspirin indications
1) ischemic stroke
2) . TIA
3) chronic stable angina
4) unstable agnina
5) coronary stenting
6) acute myocardial infarction
aspirin moa
- irreversible inhibition of COX
- decreases thromboxane a2 production thus reduces platelet activation
contradictions to aspirin
use in children and teens with viral infections (reyes syndrome)
ADR of aspirin
1) GI bleeds
2) hemorrhagic stroke
Clopidogrel (Plavix) indications:
1) acute coronary syndrome (STEMI and NSTEMI)
2) ischemic stroke
3) peripheral atherosclerotic disease
US box warning: Clopidogrel (Plavix)
diminished effects in CYP2C19 poor metabolizers
MOA Clopidogrel (Plavix)
irreversibly blocks P2Y12 component of ADP receptors on the platelet surface- effects last the duration of the platelet’s life (7-10 days)
Contraindications of Clopidogrel (Plavix)
Active pathological bleeding (peptic ulcer, intracranial hemorrhage)
Dosage for aspirin
1) 81 mg- maximal effects on platelet function
2) 325 mg- indicated in initial treatment of an acute event (chew 4 aspirin)
ADR of Clopidogrel (Plavix)
Bleeding
Metabolism/excretion of Clopidogrel (Plavix)
1) must be metabolized by CYP2C19 into active drug
2) CYP2C19 is inhibited by. PPI (drugs used to reduce stomach acid and protect the stomach from GI bleeding)
3) american college of cardiology, aha, etc. issued a consensus document that PPIs may reduce the antiplatelet effects but NOT diminish the effects
Prasugrel indications
Acute coronary syndrome
- slightly more effective than clopidogrel- BUT also had a higher risk of major bleeding
- bleeding significantly is increased in patients undergoing a CABG
- may also increase the risk of cancer
DRUG INTERACTIONS OF CLOPIDOGREL
- PPIs are used to reduce stomach acid production and to protect the stomach from GI bleeding. But, the 2c19 it inhibited by ppis.
- however, we found out that ppis might reduce the antiplatelet effect but not enough to diminish the effects
Prasugrel MOA
irreversibly blocks P2Y12. component of ADP receptors on the platelet surface- effects last the duration of the platelets life (7-10. days)
Prasugrel contradictions
active pathological bleeding (peptic ulcer, intracranial hemmorhage) prior TIA or stroke
ADR Prasugrel
Bleeding
Prasugrel US box warning
Bleeding risk
1) significant sometimes fatal bleeding- avoid in patients with active pathological bleeding or a hx of TIA or stroke
2) in patients 75+ use is generally not recommended
3) do not use in patients likely need urgent CABG sx- d/c 7 day prior to sx (most agents are 5)
4) additional risk factors for bleeding, low body weight, propensity to bleed or hx of bleeding, concomitant medications that increase risk of bleeding
5) suspect bleeding in any patient who is hypotensive
6) IF POSSIBLE, MANAGE BLEEDING WITHOUT D/C PRASUGREL- D/C INCREASES THE RISK OF A SECONDARY EVENT
Ticagrelor Indications
ACS, primary prevention of. ischemic cv events in CAD, minor ischemic stroke or high risk TIA
-more effective than clopidogrel (but fatal IC hemorrhage)
US box warning ticagrelor
IMPORTANT
1) bleeding risk
2) ASPIRIN DOSES >100 MG CAN REDUCE THE EFFECTIVENESS OF TICAGRELOR AND SHOULD BE AVOIDED ( USE 81MG DOSE ASPIRIN INSTEAD)
MOA of ticagrelor
reversible P2Y12 inhibition-reduces platelet aggregation
-inhibition of platelet aggregation is around 60% 24 hours after d/c of maintenance dosing
contraindications of ticagrelor
active pathological bleeding or hx of ich
ADR of ticagrelor
dyspnea
cangrelor indications
used in patients who remain a high risk of thrombotic event and cannot tolerate a P2Y12 or at times used in cardiogenic shock
cangrelor moa
Reversible P2Y12 inhibition- reduces platelet activation
- activation in 2 minutes (ONLY IV AGENT)
- total effects end about 1 hour after d/c
- transition to p2y12 (stop cangrelor and immediately start oral agent)
contradictions of cangrelor
signficant active bleeding
ADR cangrelor
bleeding
vorapaxar indications
history of MI or established peripheral artery disease
-reduce thrombotic event in combination with clopidogrel or aspirin (or both)
vorapaxar MOA
PAR-1 antagonist- inhibit platelet aggregation
contradictions of vorapaxar
hx of stroke, tia,ic hemm
ADR vorapaxar
bleeding
glycoprotein iib/iiia inhibitors
eptifibitide and tirofibam
glycoprotein iib/iiia inhibitors indications
the most effective antiplatelet drugs
- prevent ischemic events in those undergoing PCI- prevent re-occlusion following coronary artery revascularization with PCI- typically used on primary PCI facilities
US box warnings: glycoprotein iib/iiia inhibitors
none
glycoprotein iib/iiia inhibitors MOA
reversible blockade of GP iib/iiia receptors on platelets and thereby inhibit the final step of aggregation
- prevent aggregation stimulated by all factors including collagen…
contraindications: glycoprotein iib/iiia inhibitors
1) active abnormal bleeding within the previous 30 days or a hx of bleeding diathesis
2) hx of stroke within 30 days or hx of hemorrhagic stroke
3) severe HTN
4) major sx within the preceding 6 weeks
dipyridamole/aspirin (aggrenox) indications
prevent. recurrent stroke or tia
- shown more effective than either drug alone - the clinical trial was tainted by scientific scandal
dipyridamole/aspirin (aggrenox) us box warnings
none
dipyridamole/aspirin (aggrenox) MOA
dipyridamole inhibits the uptake of adenosine into platelets- prevents platelet activation/ aggregation
dipyridamole/aspirin (aggrenox) contradictions
same as aspirin
route dipyridamole/aspirin (aggrenox)
oral capsules
- note: there is not enough aspirin for primary prevention of MI (ony 50mg and you need > 80 mg)
