A white, capsule-shaped tablet debossed with IP 190 on one side and 500 on the other is prescription-strength Naproxen 500 mg, manufactured by Amneal Pharmaceuticals.
Identification
Attribute – Specification
- Active Ingredient – Naproxen (500 mg)
- Imprint – IP 190 on the obverse, 500 on the reverse
- Color & Shape – White, capsule-shaped / oval, biconvex tablet
- Dimensions – Approximately 16 mm in length
- Drug Class – Nonsteroidal Anti-inflammatory Drug (NSAID); propionic acid derivative
- Manufacturer – Amneal Pharmaceuticals LLC
- Controlled Substance Status – Non-controlled (Rx prescription strength)
Mechanism of Action
Naproxen is a non-selective NSAID that exerts analgesic, antipyretic, and anti-inflammatory effects by inhibiting cyclooxygenase enzymes:
- Inhibition of COX-1 and COX-2: Naproxen reversibly inhibits both cyclooxygenase-1 (constitutive) and cyclooxygenase-2 (inducible) isozymes. This blocks the catalytic conversion of arachidonic acid to endoperoxides , thereby suppressing the downstream synthesis of pro-inflammatory prostaglandins , prostacyclin , and thromboxane .
- Pain & Inflammation Reduction: By decreasing prostaglandin concentrations in peripheral tissues and the central nervous system, naproxen suppresses peripheral nociceptor sensitization and attenuates the cardinal signs of inflammation (swelling, erythema, hyperalgesia).
- Antipyretic Effect: Inhibits hypothalamic synthesis, resetting the body’s thermoregulatory center.
- Pharmacokinetics: Has an elimination half-life of 12 to 17 hours, allowing for twice-daily dosing. It is heavily bound to plasma albumin (>99%) and metabolized primarily by the liver into 6-O-desmethylnaproxen before renal excretion.
Indications and Dosage
Prescription 500 mg naproxen is indicated for managing acute pain, inflammatory musculoskeletal disorders, and arthritis.
- Osteoarthritis, Rheumatoid Arthritis, and Ankylosing Spondylitis:
- Typical dose: 500 mg orally twice daily (every 12 hours) or 250 mg to 500 mg twice daily.
- During acute exacerbations, doses may be temporarily adjusted up to 1,500 mg/day under medical supervision.
- Acute Gout:
- Initial loading dose of 750 mg, followed by 250 mg every 8 hours until the acute attack resolves.
- Acute Tendonitis, Bursitis, and Mild-to-Moderate Pain (including Dysmenorrhea):
- Starting dose: 500 mg orally once, followed by 250 mg every 6 to 8 hours or 500 mg every 12 hours as needed. Maximum daily dose on day one should not exceed 1,250 mg; subsequent daily doses should not exceed 1,000 mg unless prescribed.
- Administration: Take with a full glass of water. Taking with food, milk, or an antacid may help mitigate gastrointestinal upset.
Side Effects
Common Side Effects
- Dyspepsia, heartburn, epigastric distress, and abdominal pain
- Nausea, constipation, or mild diarrhea
- Dizziness, drowsiness, and lightheadedness
- Peripheral edema (fluid retention in extremities)
- Headache
- Tinnitus (ringing in the ears)
Serious Adverse Reactions
- Gastrointestinal Ulceration & Perforation: Occult or overt bleeding, hematemesis (vomiting blood), melena (black, tarry stools).
- Renal Impairment: Acute kidney injury, interstitial nephritis, and renal papillary necrosis, particularly in dehydrated or elderly individuals.
- Cardiovascular Events: Increased risk of myocardial infarction, stroke, new-onset hypertension, or worsening of congestive heart failure.
- Severe Dermatologic Reactions: Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS).
- Hematologic Effects: Inhibited platelet aggregation and prolonged bleeding times.
Precautions and Warnings
- FDA Boxed Warnings:
- Cardiovascular Risk: NSAIDs elevate the risk of serious, potentially fatal cardiovascular thrombotic events, myocardial infarction, and stroke. This risk can manifest early in treatment and escalates with longer duration and higher doses. Contraindicated for perioperative pain management in coronary artery bypass graft (CABG) surgery.
- Gastrointestinal Risk: NSAIDs carry high risks of severe adverse events including inflammation, ulceration, bleeding, and gastric/intestinal perforation, which can occur without prior warning symptoms.
- Renal Toxicity: Long-term administration can lead to renal papillary necrosis. Prostaglandin inhibition diminishes renal blood flow, posing acute risks to patients with baseline renal impairment, heart failure, hypovolemia, or those using ACE inhibitors/ARBs and diuretics.
- Pregnancy Warning: Avoid use starting at 20 weeks of gestation (risk of fetal oligohydramnios) and strictly contraindicate after 30 weeks due to the risk of premature closure of the fetal ductus arteriosus.
- Drug Interactions:
- Anticoagulants/Antiplatelets (e.g., Warfarin, Aspirin, DOACs): Synergistically magnifies the risk of major upper GI bleeding.
- Lithium: Reduces renal lithium clearance, potentially provoking lithium toxicity.
- Methotrexate: Decreases methotrexate elimination, increasing severe bone marrow and renal toxicity.
- Antihypertensives: Attenuates the blood-pressure-lowering efficacy of ACE inhibitors, angiotensin receptor blockers, and beta-blockers.