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Saturday, August 16, 2025

Naproxen


Naproxen is a widely used non-steroidal anti-inflammatory drug (NSAID) belonging to the propionic acid derivatives. It is valued for its potent anti-inflammatory, analgesic, and antipyretic effects. Naproxen is indicated in a wide range of musculoskeletal and inflammatory conditions, including rheumatoid arthritis, osteoarthritis, ankylosing spondylitis, gout, dysmenorrhea, and acute musculoskeletal pain.

Naproxen is available both prescription-only (higher doses for chronic inflammatory diseases) and over-the-counter (lower-dose formulations for temporary pain and fever relief). Compared to some other NSAIDs, naproxen has a relatively long half-life, allowing twice-daily dosing.

Pharmacological Classification

  • Class: Non-steroidal anti-inflammatory drug (NSAID)

  • Subclass: Propionic acid derivative

  • ATC code: M01AE02

  • Formulations:

    • Tablets (250 mg, 375 mg, 500 mg)

    • Naproxen sodium (220 mg OTC, 275 mg, 550 mg – faster absorption for acute pain)

    • Oral suspension (125 mg/5 mL, 250 mg/5 mL)

    • Suppositories and injectable forms (less common, in some regions)

Mechanism of Action

Naproxen acts by reversible inhibition of cyclooxygenase enzymes (COX-1 and COX-2):

  1. COX-1 inhibition → Decreases prostaglandins involved in gastric mucosal protection and platelet aggregation (increases risk of gastrointestinal irritation and bleeding).

  2. COX-2 inhibition → Reduces prostaglandins that mediate pain, fever, and inflammation.

Overall effects:

  • Anti-inflammatory: Reduces swelling and joint inflammation.

  • Analgesic: Relieves mild to moderate pain.

  • Antipyretic: Reduces fever.

Unlike aspirin, naproxen does not irreversibly inhibit platelet function, though it can prolong bleeding time transiently.

Pharmacokinetics

  • Absorption: Rapid and nearly complete after oral administration.

  • Onset of action: 30–60 minutes (faster with naproxen sodium).

  • Bioavailability: ~95%.

  • Distribution: Highly protein bound (~99%).

  • Metabolism: Extensively metabolized in the liver to inactive metabolites.

  • Elimination: Excreted mainly via urine.

  • Half-life: 12–15 hours (longer than ibuprofen, allowing twice-daily dosing).

Clinical Indications

  1. Rheumatic and musculoskeletal disorders

    • Rheumatoid arthritis

    • Osteoarthritis

    • Ankylosing spondylitis

    • Juvenile idiopathic arthritis

  2. Acute musculoskeletal pain

    • Sprains, strains, back pain, and soft-tissue injuries

  3. Acute gout

    • Effective in reducing inflammation and pain during gout flares

  4. Dysmenorrhea

    • Relief of menstrual cramps by reducing prostaglandin-mediated uterine contractions

  5. Headache and migraine

    • Sometimes used as part of acute migraine therapy

  6. Fever and mild-to-moderate pain (OTC use)

    • Short-term symptomatic relief of pain and pyrexia

Contraindications

  • Known hypersensitivity to naproxen, aspirin, or other NSAIDs

  • History of peptic ulcer disease, gastrointestinal bleeding, or perforation

  • Active gastrointestinal hemorrhage or ulceration

  • Severe heart failure

  • Severe renal impairment (creatinine clearance <30 mL/min)

  • Severe hepatic impairment

  • History of NSAID-induced asthma, urticaria, or allergic-type reactions

  • Third trimester of pregnancy (risk of premature closure of ductus arteriosus)

Precautions

  • Elderly patients: Higher risk of gastrointestinal bleeding and renal complications.

  • Cardiovascular disease: Prolonged use may increase risk of thrombotic events (MI, stroke).

  • Gastrointestinal risk: Use with caution in patients with history of ulcers; co-prescribe gastroprotective agents (e.g., PPIs) when appropriate.

  • Renal impairment: NSAIDs can worsen renal function through prostaglandin inhibition.

  • Hepatic impairment: Dose adjustment and monitoring required.

  • Pregnancy: Contraindicated in the third trimester; avoid if possible in first and second trimesters.

  • Breastfeeding: Naproxen is excreted in small amounts in breast milk; occasional short-term use is usually acceptable, but long-term use is discouraged.

Adverse Effects

Common

  • Dyspepsia, nausea, vomiting

  • Abdominal pain

  • Heartburn, indigestion

  • Headache, dizziness, drowsiness

  • Rash

Less Common

  • Diarrhea or constipation

  • Tinnitus

  • Edema due to fluid retention

  • Elevated liver enzymes

Serious

  • Gastrointestinal bleeding, ulceration, perforation

  • Severe allergic reactions (anaphylaxis, bronchospasm, angioedema)

  • Stevens-Johnson syndrome (rare)

  • Renal impairment or acute kidney injury

  • Hepatotoxicity

  • Increased cardiovascular risk with long-term or high-dose use

Drug Interactions

  • Other NSAIDs or aspirin: Increased risk of GI toxicity without added benefit.

  • Anticoagulants (e.g., warfarin, DOACs): Increased bleeding risk.

  • Antiplatelet drugs (clopidogrel, aspirin): Additive bleeding risk.

  • Corticosteroids: Increased gastrointestinal side effects.

  • SSRIs: Increased GI bleeding risk.

  • Antihypertensives (ACE inhibitors, ARBs, beta-blockers, diuretics): May reduce antihypertensive effect; increased risk of nephrotoxicity.

  • Lithium: Reduced renal clearance → lithium toxicity.

  • Methotrexate: Reduced clearance → risk of methotrexate toxicity.

Dosage

Adults

  • Rheumatic disorders / chronic conditions:

    • 500 mg to 1,000 mg daily in divided doses (250–500 mg twice daily).

  • Acute pain / dysmenorrhea:

    • Initial dose: 500 mg, followed by 250 mg every 6–8 hours as needed.

    • Maximum: 1,250 mg on the first day, then up to 1,000 mg daily.

  • Acute gout:

    • 750 mg initially, followed by 250 mg every 8 hours until the attack subsides.

Children (for juvenile arthritis)

  • 10 mg/kg/day in two divided doses (maximum 1,000 mg/day).

Elderly

  • Use the lowest effective dose for the shortest possible duration; greater susceptibility to adverse effects.

OTC Use

  • Naproxen sodium 220 mg every 8–12 hours as needed for pain or fever.

  • Maximum 660 mg/day for short-term OTC use.

Clinical Efficacy

  • Rheumatic disease: Strong anti-inflammatory and analgesic effects comparable to other NSAIDs; twice-daily dosing improves adherence.

  • Gout: Rapid symptom relief in acute flares.

  • Dysmenorrhea: Demonstrated superior efficacy compared to placebo in reducing menstrual pain.

  • Migraine: Effective in some patients, especially when taken early in attacks.

  • Safety profile: GI and CV risks are present but lower compared to some NSAIDs like indomethacin or diclofenac; however, GI toxicity remains a major concern.

Patient Counseling Points

  • Take with food, milk, or water to minimize stomach irritation.

  • Do not exceed prescribed dose or duration.

  • Report symptoms of gastrointestinal bleeding (black stools, vomiting blood).

  • Avoid alcohol, as it increases GI bleeding risk.

  • Avoid concomitant use with other NSAIDs unless prescribed.

  • Seek medical advice if experiencing chest pain, shortness of breath, weakness, or slurred speech (possible CV event).




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