NAPRELAN- naproxen sodium tablet, film coated, extended release
Shionogi Inc.


(naproxen sodium)


Equivalent to 375 mg, 500 mg and 750 mg naproxen

NAPRELAN® Controlled-Release Tablets, 375 mg, 500 mg and 750 mg


  • NSAIDs may cause an increased risk of serious cardiovascular thrombotic events, myocardial infarction, and stroke, which can be fatal. This risk may increase with duration of use. Patients with cardiovascular disease or risk factors for cardiovascular disease may be at greater risk. ( s ee WARNINGS ).
  • Naproxen as NAPRELAN ® is contraindicated for the treatment of peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery ( s ee WARNINGS ).


  • NSAIDs cause an increased risk of serious gastrointestinal adverse events including bleeding, ulceration, and perforation of the stomach or intestines, which can be fatal. These events can occur at any time during use and without warning symptoms. Elderly people are at greater risk for ser i ous gastrointestinal events. ( s ee WARNINGS ).


NAPRELAN®* Tablets contain naproxen sodium, a member of the arylacetic acid group of nonsteroidal anti-inflammatory drugs (NSAIDs). NAPRELAN® Tablets use the proprietary IPDAS®** (Intestinal Protective Drug Absorption System) technology. It is a rapidly disintegrating tablet system combining an immediate release component and a sustained release component of microparticles that are widely dispersed, allowing absorption of the active ingredient throughout the gastrointestinal (GI) tract, maintaining blood levels over 24 hours. The chemical name for naproxen sodium is 2-naphthaleneacetic acid, 6-methoxy-a-methyl-sodium salt, (S)- with the following structural formula:

Naproxen sodium structural formula
(click image for full-size original)

Naproxen sodium is an odorless crystalline powder, white to creamy in color. It is soluble in methanol and water. NAPRELAN® Tablets contain 412.5 mg, 550 mg, or 825 mg of naproxen sodium, equivalent to 375 mg, 500 mg, and 750 mg of naproxen and 37.5, mg 50 mg, and 75 mg sodium respectively. Each NAPRELAN® Tablet also contains the following inactive ingredients: ammoniomethacrylate copolymer Type A, ammoniomethacrylate copolymer Type B, citric acid, crospovidone, magnesium stearate, methacrylic acid copolymer Type A, microcrystalline cellulose, povidone, and talc. The tablet coating contains hydroxypropyl methylcellulose, polyethylene glycol, and titanium dioxide.


Naproxen is a nonsteroidal anti-inflammatory drug (NSAID), with analgesic and antipyretic properties. As with other NSAIDs, its mode of action is not fully understood; however, its ability to inhibit prostaglandin synthesis may be involved in the anti-inflammatory effect.


Although naproxen itself is well absorbed, the sodium salt form is more rapidly absorbed, resulting in higher peak plasma levels for a given dose. Approximately 30% of the total naproxen sodium dose in NAPRELAN® Tablets is present in the dosage form as an immediate release component. The remaining naproxen sodium is coated as microparticles to provide sustained release properties. After oral administration, plasma levels of naproxen are detected within 30 minutes of dosing, with peak plasma levels occurring approximately 5 hours after dosing. The observed terminal elimination half-life of naproxen from both immediate release naproxen sodium and NAPRELAN® Tablets is approximately 15 hours. Steady state levels of naproxen are achieved in 3 days and the degree of naproxen accumulation in the blood is consistent with this.

Plasma Naproxen Concentrations Mean of 24 Subjects (+/-2SD) (Steady State, Day 5)
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Plasma Naproxen Concentrations Mean of 24 Subjects (+/-2SD) (Steady State, Day 5)

Pharmacokinetic Parameters at Steady State Day 5 (Mean of 24 Subjects)
Parameter(units)naproxen 500 mgQ12h/5 days (1000 mg)NAPRELAN® 2 x 500 mg tablets(1000 mg) Q24h/5 days
AUC 0-24(mcgxh/mL)14461681167 — 185814481451173 — 1774
Cmax (mcg/mL)951371 — 117941374 — 127
Cavg (mcg/mL)60749 — 7760649 — 74
Cmin (mcg/mL)36913 — 5133723 — 48
Tmax (hrs)311 — 4522-10


Naproxen itself is rapidly and completely absorbed from the GI tract with an in vivo bioavailability of 95%. Based on the pharmacokinetic profile, the absorption phase of NAPRELAN® Tablets occurs in the first 4-6 hours after administration. This coincides with disintegration of the tablet in the stomach, the transit of the sustained release microparticles through the small intestine and into the proximal large intestine. An in vivo imaging study has been performed in healthy volunteers that confirms rapid disintegration of the tablet matrix and dispersion of the microparticles.

The absorption rate from the sustained release particulate component of NAPRELAN® Tablets is slower than that for conventional naproxen sodium tablets. It is this prolongation of drug absorption processes that maintains plasma levels and allows for once daily dosing.

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