NAPROSYN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for NAPROSYN (NAPROSYN).
Nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX-1 and COX-2) enzymes, thereby reducing prostaglandin synthesis. This results in decreased inflammation, pain, and fever.
| Metabolism | Extensively metabolized in the liver via glucuronidation and oxidation; CYP450 involvement is minor. Major metabolite is 6-desmethylnaproxen. |
| Excretion | Renal excretion of conjugated metabolites accounts for approximately 95% of a dose, with 1-2% as unchanged naproxen. Fecal excretion is minimal (<5%). |
| Half-life | Terminal elimination half-life is 12-17 hours. This long half-life allows twice-daily dosing, but may lead to drug accumulation in elderly or renally impaired patients. |
| Protein binding | >99% bound to albumin. |
| Volume of Distribution | 0.16 L/kg (approximately 10-12 L in a 70 kg adult). Low Vd indicates distribution primarily in plasma and extracellular fluid. |
| Bioavailability | Oral: 95% (completely absorbed). Rectal: approximately 80% of oral bioavailability. |
| Onset of Action | Oral: 1-2 hours for analgesic effect. Rectal: similar to oral, 1-2 hours. |
| Duration of Action | Analgesic effect lasts up to 12 hours. Anti-inflammatory effect may persist longer with repeated dosing. |
| Action Class | NSAID's- Non-Selective COX 1&2 Inhibitors (propionic acid) |
| Brand Substitutes | Naptrox 250mg Tablet, Naprostar 250mg Tablet, Nalyxan 250mg Tablet, Naprozee 250mg Tablet, Antesvel 250mg Tablet, Xenobid Gel |
250-500 mg orally twice daily; maximum 1500 mg/day. For extended-release: 750-1000 mg orally once daily.
| Dosage form | SUSPENSION |
| Renal impairment | GFR 30-59 mL/min: decrease dose by 50% or use alternative; GFR <30 mL/min: contraindicated. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | For juvenile arthritis: 10-15 mg/kg/day divided twice daily; maximum 1000 mg/day. For other indications: 5-10 mg/kg/dose every 8-12 hours. |
| Geriatric use | Start at lowest effective dose (250 mg twice daily); monitor renal function and gastrointestinal bleeding risk. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for NAPROSYN (NAPROSYN).
| Breastfeeding | Naproxen is excreted into breast milk in small amounts (M/P ratio approximately 0.01). The relative infant dose is about 1% of the maternal weight-adjusted dose. Use with caution in breastfeeding; monitor infant for gastrointestinal effects, rash, or bleeding. |
| Teratogenic Risk | First trimester: Case-control studies suggest a small increased risk of cardiac defects and oral clefts; absolute risk remains low. Second/third trimester: Exposure may cause premature constriction of the ductus arteriosus, oligohydramnios due to fetal renal effects, and risk of necrotizing enterocolitis, intracranial hemorrhage, and renal dysfunction in the neonate; avoid after 30 weeks gestation. |
■ FDA Black Box Warning
Increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal. Increased risk of serious gastrointestinal adverse events including bleeding, ulceration, and perforation, which can be fatal.
| Serious Effects |
["Hypersensitivity to naproxen or any component of the formulation","History of asthma, urticaria, or allergic-type reactions after taking aspirin or other NSAIDs","Perioperative pain in coronary artery bypass graft surgery","Advanced renal disease","Active peptic ulcer disease or GI bleeding"]
| Precautions | ["Cardiovascular risk: Use lowest effective dose for shortest duration; avoid in coronary artery bypass graft surgery.","Gastrointestinal risk: History of peptic ulcer disease or GI bleeding increases risk.","Renal effects: May cause renal toxicity, especially in patients with impaired renal function, heart failure, or on diuretics.","Hepatic effects: Elevation of liver enzymes may occur; discontinue if signs of hepatic toxicity.","Anaphylactoid reactions: May occur in patients with aspirin sensitivity.","Hypertension: May worsen blood pressure control.","Fluid retention: Use with caution in patients with heart failure or hypertension.","Hematologic effects: May inhibit platelet aggregation; monitor for bleeding."] |
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| Fetal Monitoring | Monitor maternal renal function and blood pressure regularly. In third trimester, assess amniotic fluid volume (oligohydramnios). Fetal echocardiography for ductus arteriosus constriction if used beyond 30 weeks. Neonatal monitoring for bleeding, renal function, and gastrointestinal symptoms. |
| Fertility Effects | Reversible inhibition of ovulation due to effects on prostaglandin synthesis; use may impair fertility in women attempting conception, but effect ceases upon discontinuation. |