NSAID (Non-selective COX Inhibitor) Pregnancy: Contraindicated during pregnancy. Inhibition of prostaglandin synthesis may adversely affect the pregnancy and/or embryo/foetal development; epidemiological data suggest an increased risk of miscarriage, cardiac malformation and gastroschisis after use in early pregnancy. From the 20th week of pregnancy onward, use may cause oligohydramnios resulting from foetal renal dysfunction, and ductus arteriosus constriction has been reported following second-trimester treatment. During the first and second trimester naproxen should not be given unless clearly necessary and, if used, the dose kept as low and duration as short as possible, with antenatal monitoring for oligohydramnios and ductus arteriosus constriction considered after several days of exposure from gestational week 20 onward. During the third trimester all prostaglandin synthesis inhibitors may expose the foetus to cardiopulmonary toxicity (premature constriction/closure of the ductus arteriosus and pulmonary hypertension) and renal dysfunction, and the mother and neonate to possible prolongation of bleeding time and inhibition of uterine contractions. Naproxen has been found in the milk of lactating women and use should be avoided in patients who are breast-feeding. May impair fertility; not recommended in women attempting to conceive.

Naproxen

Brand names: Naprosyn, Anaprox, Feminax Ultra

Used in: Headache & Migraine Gout

Naproxen is a non-steroidal anti-inflammatory drug (NSAID) used for pain and inflammation, including musculoskeletal conditions and acute gout.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 500 mg to 1 g daily (rheumatoid arthritis, osteoarthritis and ankylosing spondylitis)

Route: Oral (to be taken preferably with or after food)

Frequency: In 2 doses at 12-hour intervals, or alternatively as a single administration

Max: For acute musculoskeletal disorders and dysmenorrhoea, a maximum daily dose after the first day of 1250 mg

Source: Naproxen 250 mg Tablets (UK SPC). Undesirable effects may be minimised by using the lowest effective dose for the shortest duration necessary to control symptoms. Rheumatoid arthritis, osteoarthritis and ankylosing spondylitis: 500 mg to 1 g taken in 2 doses at 12-hour intervals or alternatively as a single administration. A loading dose of 750 mg or 1 g per day for the acute phase is recommended (a) in patients reporting severe night-time pain and/or morning stiffness, (b) in patients being switched to naproxen from a high dose of another anti-rheumatic compound, and (c) in osteoarthrosis where pain is the predominant symptom. Acute gout: 750 mg at once then 250 mg every 8 hours until the attack has passed. Acute musculoskeletal disorders and dysmenorrhoea: 500 mg initially followed by 250 mg at 6-8 hour intervals as needed, with a maximum daily dose after the first day of 1250 mg. Older people: although total plasma concentration of naproxen is unchanged, the unbound plasma fraction is increased in older people and the implication for dosing is unknown; it is prudent to use the lowest effective dose for the shortest duration possible as older people are more prone to adverse events, and the patient should be monitored regularly for GI bleeding during NSAID therapy. Renal/hepatic impairment: a lower dose should be considered. Treatment should be reviewed at regular intervals and discontinued if no benefit is seen or intolerance occurs.

Paediatric dose

Dose: 10 mg/kg

Route: Oral

Frequency: Per day, taken in 2 doses at 12-hour intervals

Paediatric population (over 5 years), for juvenile rheumatoid arthritis: 10 mg/kg/day taken in 2 doses at 12-hour intervals. Naproxen is not recommended for use in any other indication in children under 16 years of age. Verify against a children's formulary.

Dose adjustments

Renal

A lower dose should be considered in patients with renal or hepatic impairment. Contraindicated in patients with baseline creatinine clearance less than 30 ml/minute, because accumulation of naproxen metabolites has been seen in patients with severe renal failure or those on dialysis. Also contraindicated in severe renal failure.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

Patient weight (kg)

Verify in a children's formulary

US labelling (FDA)

Reference — US labelling, may differ from UK

Use the lowest effective dosage for shortest duration consistent with individual patient treatment goals. ( 2.1 ) Rheumatoid Arthritis, Osteoarthritis, and Ankylosing Spondylitis Naproxen tablets 250 mg (one-half tablet) 500 mg twice daily Naproxen sodium tablets 275 mg (one-half tablet) 550 mg twice daily The dose may be adjusted up or down depending on the clinical response of the patient. In patients who tolerate lower doses well, the dose may be increased to naproxen 1500 mg/ day for up to 6 months. Polyarticular Juvenile Idiopathic Arthritis Naproxen tablets may not allow for the flexible dose titration needed in pediatric patients with polyarticular juvenile idiopathic arthritis. A …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2026-01-29. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Active or history of peptic ulceration or active gastrointestinal bleeding (two or more distinct episodes of proven ulceration or bleeding)
History of gastrointestinal bleeding or perforation related to previous NSAID therapy
Hypersensitivity to naproxen or any of the excipients
Patients in whom aspirin or other NSAIDs induce the syndrome of asthma, rhinitis, nasal polyps or urticaria (potential for cross-sensitivity reactions, which have the potential of being fatal)
Severe renal, hepatic or heart failure
During pregnancy (contraindicated during the last trimester; see section 4.6)

Side effects

Gastrointestinal (most commonly observed): heartburn, nausea, vomiting, constipation, diarrhoea, flatulence, dyspepsia, abdominal discomfort and epigastric distress; more serious reactions include GI bleeding (sometimes fatal, particularly in older people), ulceration, perforation and obstruction, melaena, haematemesis, exacerbation of ulcerative colitis and Crohn's disease, oesophagitis, gastritis and pancreatitis
Hypersensitivity reactions: nonspecific allergic reactions and anaphylaxis; respiratory tract reactivity including asthma, aggravated asthma, bronchospasm or dyspnoea; skin disorders including rashes, pruritus, urticaria, purpura, angio-oedema and, more rarely, exfoliative and bullous dermatoses (including epidermal necrolysis and erythema multiforme)
Nervous system: convulsions, dizziness, headache, lightheadedness, drowsiness, paraesthesia, retrobulbar optic neuritis, inability to concentrate and cognitive dysfunction; aseptic meningitis (especially in patients with existing auto-immune disorders)
Cardiac/vascular: oedema, palpitations, cardiac failure and congestive heart failure; hypertension, vasculitis. Clinical trial and epidemiological data suggest that use of coxibs and some NSAIDs (particularly at high doses and in long-term treatment) may be associated with a small increased risk of arterial thrombotic events (e.g. myocardial infarction or stroke)
Blood and lymphatic system: neutropenia, thrombocytopenia, granulocytopenia including agranulocytosis, eosinophilia, leucopenia, aplastic anaemia and haemolytic anaemia. Hepatobiliary: jaundice, fatal hepatitis and abnormal liver function tests

Interactions

Anticoagulants such as warfarin — synergistic effect on bleeding; increased risk of serious bleeding compared with either drug alone; monitor for signs of bleeding (US labelling)
Antiplatelet agents (e.g. aspirin), SSRIs and SNRIs — concomitant use may potentiate the risk of bleeding more than an NSAID alone; monitor for signs of bleeding (US labelling)
Aspirin — a pharmacodynamic study demonstrated that lower-dose naproxen (220 mg/day or 220 mg twice daily) interfered with the antiplatelet effect of low-dose immediate-release aspirin, the interaction being most marked during the naproxen washout period (US labelling)

Clinical monograph

How it works

It non-selectively inhibits cyclo-oxygenase (COX-1 and COX-2), reducing prostaglandin synthesis.

Prescribing in practice

Among the NSAIDs it has a relatively favourable cardiovascular risk profile, but the usual gastrointestinal and renal cautions still apply.
Use the lowest effective dose for the shortest time, with gastroprotection in at-risk patients; avoid in significant renal impairment, heart failure and active peptic ulceration.
It adds to bleeding risk with anticoagulants and antiplatelets.

Monitoring

With longer use or in at-risk patients monitor renal function and blood pressure; review gastrointestinal symptoms.

Counselling the patient

Take it with or after food.
Report indigestion, black stools or reduced urine output.
Avoid combining it with other NSAIDs.

Evidence & guidelines

An effective NSAID often preferred where cardiovascular risk is a concern, at the lowest effective dose for the shortest time.

Reference: NICE CG177 (Osteoarthritis); NICE NG146 (Rheumatoid Arthritis); Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Diclofenac sodium · NSAID (non-selective COX inhibitor)

Pathways