Platelet inhibitory effects of OTC doses of naproxen sodium compared with prescription dose naproxen sodium and low-dose aspirin

Abstract

Objectives: 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).

Research design and 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.

Primary outcome measure: Inhibition of serum thromboxane B₂ (TXB₂), 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 TXB₂ was 47% for placebo and ≥98% for all doses of NAPSO. After 7 days of EC-ASA 81 mg, mean inhibition of TXB₂ was ≥ 97% (period 2).

Study limitations: 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).

Key words: :

• Aspirin
• Naproxen sodium
• Platelet inhibition
• Thromboxane B₂

Transparency

Declaration of funding

Bayer HealthCare, Consumer Care Division, funded the study and had a role in the study design and writing of the manuscript.

Declaration of financial/other relationships

M.S. has declared that he is a consultant and speaker for Bayer HealthCare. M.C.H. has declared that he has received research support from the American College of Rheumatology, Arthritis Foundation and National Institutes of Health; and that he is a consultant to AstraZeneca, Bayer HealthCare, CombinatoRx, Endo Pharmaceuticals, Merck, NicOx S.A., Novartis, Pfizer and Pozen. J.O. has declared that he is an employee of Kendle Early Stage – Toronto. K.B. has declared that he is a consultant, and has received research support from, sanofi-aventis, Bayer HealthCare, GlaxoSmithKline, Merck, Novartis, and Pfizer. The sponsor did not have a role in the collection, management, or analysis of the data.

All peer reviewers receive honoraria from CMRO for their review work. The peer reviewers have disclosed that they have no relevant financial relationships.

Acknowledgment

The authors thank Lorraine R. Baer, PharmD for her writing and editorial assistance and Reinhard Schuller, PhD for his contribution to the statistical analysis.

Some data have been previously presented as posters at 70th Annual Meeting of the American College of Rheumatology, Washington, DC, November 11–15, 2006; and 2006 OARSI World Congress on Osteoarthritis, Prague, Czech Republic, December 7–10, 2006.