title: Platelet inhibitory effects of OTC doses of naproxen sodium compared with prescription dose naproxen sodium and low-dose aspirin.
abstract: OBJECTIVE
  Prescription dose naproxen has been reported to have an antiplatelet effect similar to low-dose aspirin (ASA). This study evaluated the platelet inhibitory effects of over-the-counter (OTC) doses of naproxen sodium (NAPSO) compared to that of a prescription dose of NAPSO and to low-dose enteric-coated aspirin (EC-ASA).
  
  
  METHODS
  This was a phase I, open-label, randomized, placebo-controlled, two-way crossover, multi-dose, pharmacodynamic trial conducted in healthy male and female volunteers (n = 48, mean age = 41.7 years). All subjects received 7 days of either prescription dose NAPSO (550 mg twice daily), OTC doses of NAPSO (220 mg two or three times daily), or placebo twice daily (period 1). After a minimum 6-day washout period, all subjects then received 7 days of EC-ASA 81 mg once daily (period 2). All study medications were taken by mouth.
  
  
  METHODS
  Inhibition of serum thromboxane B(2) (TXB(2)), as a marker of platelet cyclooxygenase-1 (COX-1) inhibition, measured 24 h after the day 7 morning dose. This was measured after both period 1 and period 2.
  
  
  RESULTS
  After 7 days of treatment in period 1, mean inhibition of TXB(2) was 47% for placebo and > or =98% for all doses of NAPSO. After 7 days of EC-ASA 81 mg, mean inhibition of TXB(2) was > or = 97% (period 2).
  
  
  CONCLUSIONS
  Out-patient study setting.
  
  
  CONCLUSIONS
  These data suggest that OTC doses of NAPSO (220 mg two or three times daily) have an antiplatelet effect similar to EC-ASA 81 mg and to prescription dose NAPSO (550 mg twice daily).
authors.affiliation: University of Colorado, Denver, CO, USA. lmschiff@aol.com
authors.forename: Michael
authors.initials: M
authors.lastname: Schiff
authors.forename: Marc C
authors.initials: MC
authors.lastname: Hochberg
authors.forename: John
authors.initials: J
authors.lastname: Oldenhof
authors.forename: Kay
authors.initials: K
authors.lastname: Brune
mesh_terms: D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology* / Q000627:therapeutic use; D001241:Aspirin / Q000494:pharmacology* / Q000627:therapeutic use; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009288:Naproxen / Q000494:pharmacology* / Q000627:therapeutic use; D004366:Nonprescription Drugs; D010919:Placebos; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D012016:Reference Values; D013929:Thromboxane B2 / Q000097:blood
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D004366:Nonprescription Drugs; D010919:Placebos; D010975:Platelet Aggregation Inhibitors; D013929:Thromboxane B2; D009288:Naproxen; D001241:Aspirin