This study is being conducted to investigate the rate and extent of naproxen absorption from the Test naproxen sodium formulation is bioequivalent to Aleve® naproxen sodium, a Reference product currently marketed in The Netherlands in order to support the registration of the Reckitt Benckiser (RB) naproxen sodium (220 mg tablets).

Inclusion Criteria:

1. Male or female subjects who have given written informed consent.
2. Age: ≥ 18 years ≤ 50 years.
3. Body Mass Index (BMI) of ≥ 20 and ≤ 30 kg/m2.
4. Healthy as determined by past medical history, physical examination, vital signs, electrocardiogram (ECG), and laboratory tests at screening.
5. Female subject of child bearing potential with a negative pregnancy test at the screening visit and willing to use an effective method of contraception unless of non-childbearing potential or where abstaining from sexual intercourse in line with the preferred and usual lifestyle of the subject from first dose until 3 months after the final dose of study medication.
6. Female subject of non-child bearing potential with negative pregnancy test at the screening visit.
7. Male subject willing to use an effective method of contraception unless anatomically sterile or where abstaining from sexual intercourse in line with the preferred and usual lifestyle of the subject from first dose until 3 months after the final dose of study medication.

Exclusion Criteria:

1. Pregnant or lactating females.
2. Intention to become pregnant during the course of the study
3. Lack of safe contraception.
4. A history and/or presence of significant disease of any body system, including psychiatric disorders.
5. Any condition that may currently interfere with the absorption, distribution, metabolism or excretion of drugs.
6. A history of allergy or intolerance related to treatment with naproxen or other NSAIDs, or the excipients of the formulations.
7. A history of or active peptic or duodenal ulcers or gastro-intestinal bleed or upper gastro-intestinal bleed, or other significant gastro-intestinal disorders.
8. A history of frequent dyspepsia, e.g. heartburn or indigestion.
9. A history of migraine.
10. Current smokers and ex-smokers who have smoked or used nicotine replacement products during the previous 6 months prior to first dosing.
11. A history of substance abuse (including alcohol).
12. High consumption of stimulating drinks (coffee, tea, cola, energy drinks etc; total caffeine intake per day above 300 mg [1 cup of coffee equates to approximately 50 mg caffeine]).
13. Those with positive screen/test for drugs of abuse and alcohol.
14. Ingestion of a prescribed drug at any time in the 14 days before the first dose of study medication (excluding hormonal contraceptives and hormone replacement therapy), or consumption of enzyme inhibitors or inducers (drug, food or herb) 30 days prior to the first dose of study medication (such as barbiturates, carbamazepine, erythromycin, phenytoin, etc.).
15. Ingestion of an over-the-counter (OTC) preparation within 7 days before the first dose of study medication, including herbal medications, vitamin/fish oil supplements, naproxen and other NSAIDs.
16. Those who have consumed grapefruit or grapefruit juice, pummelo or Seville oranges in the 7 days prior to randomisation.
17. Strenuous physical exercise from 48 hours prior to randomisation to the post study Follow-Up Visit.
18. Donation of blood in quantity > 400 ml or other blood products e.g. to the blood transfusion service or significant loss of blood in the 12 weeks prior to screening.
19. Known human immunodeficiency virus (HIV) positive status, or a positive viral serology screen.
20. Topical use of naproxen within 7 days before the first dose of study medication.
21. Those previously randomised into this study.
22. Those who are an employee at the study site.
23. Those who are a partner or first degree relative of the Investigator.
24. Receipt of an investigational product, or participation in another trial involving a marketed or investigational drug in the 12 weeks prior to screening.
25. Those unable in the opinion of the Investigator to comply fully with the study requirements.

Up to follow-up day 7

Treatment-emergent adverse events (TEAEs), i.e., existing conditions that worsened or events that occurred during the course of the study after first administration of IMP and before the end of the study, are included.