title: Aspirin has little additional anti-platelet effect in healthy volunteers receiving prasugrel.
abstract: BACKGROUND
  Strong P2Y(12) blockade, as can be achieved with novel anti-platelet agents such as prasugrel, has been shown in vitro to inhibit both ADP and thromboxane A(2) -mediated pathways of platelet aggregation, calling into question the need for the concomitant use of aspirin.
  
  
  OBJECTIVE
  The present study investigated the hypothesis that aspirin provides little additional anti-aggregatory effect in a group of healthy volunteers taking prasugrel. STUDY PARTICIPANTS/METHODS: In all, 9 males, aged 18 to 40 years, enrolled into the 21-day study. Prasugrel was loaded at 60 mg on day 1 and maintained at 10 mg until day 21. At day 8, aspirin 75 mg was introduced and the dose increased to 300 mg on day 15. On days 0, 7, 14 and 21, platelet function was assessed by aggregometry, response to treatments was determined by VerifyNow and urine samples were collected for quantification of prostanoid metabolites.
  
  
  RESULTS
  At day 7, aggregation responses to a range of platelet agonists were reduced and there was only a small further inhibition of aggregation to TRAP-6, collagen and epinephrine at days 14 and 21, when aspirin was included with prasugrel. Urinary prostanoid metabolites were unaffected by prasugrel, and were reduced by the addition of aspirin, independent of dose.
  
  
  CONCLUSIONS
  In healthy volunteers, prasugrel produces a strong anti-aggregatory effect, which is little enhanced by the addition of aspirin. The addition of aspirin as a dual-therapy with potent P2Y(12) receptor inhibitors warrants further investigation.
authors.affiliation: Department of Cardiothoracic Pharmacology, Imperial College London, National Heart and Lung Institute, London, UK.
authors.forename: P D M
authors.initials: PD
authors.lastname: Leadbeater
authors.forename: N S
authors.initials: NS
authors.lastname: Kirkby
authors.forename: S
authors.initials: S
authors.lastname: Thomas
authors.forename: A-R
authors.initials: AR
authors.lastname: Dhanji
authors.forename: A T
authors.initials: AT
authors.lastname: Tucker
authors.forename: G L
authors.initials: GL
authors.lastname: Milne
authors.forename: J A
authors.initials: JA
authors.lastname: Mitchell
authors.forename: T D
authors.initials: TD
authors.lastname: Warner
mesh_terms: D000293:Adolescent; D000328:Adult; D001241:Aspirin / Q000494:pharmacology*; D006801:Humans; D008297:Male; D010879:Piperazines / Q000494:pharmacology*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D000068799:Prasugrel Hydrochloride; D058921:Purinergic P2Y Receptor Antagonists / Q000494:pharmacology*; D013876:Thiophenes / Q000494:pharmacology*; D013931:Thromboxanes / Q000096:biosynthesis
chemical_list: D010879:Piperazines; D010975:Platelet Aggregation Inhibitors; D058921:Purinergic P2Y Receptor Antagonists; D013876:Thiophenes; D013931:Thromboxanes; D000068799:Prasugrel Hydrochloride; D001241:Aspirin