Antiplatelets

Question 1

describe the MOA of aspirin

Answer 1

Irreversibly inhibits COX-1, preventing conversion of arachidonic acid to prostaglandins… no production of thromboxane A2… no platelet aggregation.

Question 2

name common indications for aspirin

Answer 2

1. secondary DVD prevention: 75 mg
2. acute management of UA, NSTEMI, STEMI, suspected TIA: 300 mg
3. management of TIA (with dipyridamole): 75 mg
4. following coronary by-pass surgery: 75-300 mg
5. mild to moderate pain or pyrexia: 300-900 mg every 4 hrs as required (max 4g/day)

Question 3

contra-indications for aspirin?

Answer 3

• <16 yrs
• current or previous peptic ulcer
• haemophilia and other bleeding disorders
• severe HF
  Caution:
• asthma
• G6PD deficiency

Question 4

ADRs of aspirin?

Answer 4

• haemorrhage, inc. GI or intracranial bleed, menorrhagia
• bronchospasms, dyspnoea
• dyspepsia, GI ulceration

Question 5

why is aspirin contra-indicated in children?

Answer 5

Risk of Reye syndrome: rapidly progressive encephalopathy + hepatitis. Risk of death or permanent brain damage.

Question 6

describe the MOA of clopidogrel

Answer 6

Antagonises P2Y12 ADP receptor, inhibiting platelet activation.

Question 7

suggest indications for clopidogrel

Answer 7

1. acute management of NSTEMI or STEMI (with aspirin): 300 mg, then 75 mg for at least 4 wks
2. secondary CVD prevention in PAD, within 35 days of MI or 6 mths of ischaemic stroke: 75 mg

Question 8

do aspirin and clopidogrel need to be stopped before surgery?

Answer 8

Aspirin: no, unless high bleeding risk procedure.

Clopidogrel: stop 7 days before elective surgery.