ANAPROX DS
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ANAPROX DS (ANAPROX DS).
Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) that inhibits cyclooxygenase (COX-1 and COX-2) enzymes, reducing prostaglandin synthesis.
| Metabolism | Hepatic metabolism primarily via CYP2C9 and minor contributions from CYP1A2 and CYP2C8. |
| Excretion | Renal elimination of naproxen and its metabolites accounts for approximately 95% of the dose, with about 60% as unchanged drug and 40% as conjugated or hydroxylated metabolites. Biliary/fecal excretion is negligible (<5%). |
| Half-life | Terminal elimination half-life is approximately 12–17 hours (mean ~14 hours), allowing twice-daily dosing. Steady-state is achieved after 4–5 doses. |
| Protein binding | >99.7% bound to albumin. Naproxen is highly protein-bound, saturable at high concentrations. |
| Volume of Distribution | Volume of distribution is approximately 0.16 L/kg, indicating limited extravascular distribution consistent with high protein binding. |
| Bioavailability | Oral bioavailability is approximately 95% (naproxen base). The sodium salt (Anaprox DS) is rapidly absorbed; food may delay absorption but does not reduce extent. |
| Onset of Action | Oral: Onset of analgesia occurs within 1–2 hours. Peak plasma concentrations are reached in 2–4 hours. |
| Duration of Action | Duration of analgesia is 7–12 hours (up to 12 hours for anti-inflammatory effect). Twice-daily dosing provides sustained relief. |
550 mg orally every 8 to 12 hours; maximum 1375 mg/day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-89 mL/min: no adjustment; GFR <30 mL/min: contraindicated. |
| Liver impairment | Child-Pugh Class A: no adjustment; Class B/C: avoid use or reduce dose to 275 mg every 12 hours. |
| Pediatric use | Children ≥12 years: 550 mg orally every 12 hours; children 2-11 years: 6.25 mg/kg every 8 hours. |
| Geriatric use | Initiate at lowest effective dose; consider 275 mg every 12 hours; monitor renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ANAPROX DS (ANAPROX DS).
| Breastfeeding | Naproxen is excreted into breast milk at low levels (relative infant dose <1%). M/P ratio is unknown. Consider alternative analgesics like ibuprofen or acetaminophen due to potential for infant adverse effects. |
| Teratogenic Risk | First trimester: Risk of cardiac defects and gastroschisis (OR 1.3-2.0). Second trimester: Increased risk of oligohydramnios. Third trimester: Premature closure of ductus arteriosus, oligohydramnios, neonatal pulmonary hypertension, and renal impairment. Avoid after 30 weeks gestation. |
■ FDA Black Box Warning
Nonsteroidal anti-inflammatory drugs (NSAIDs) cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal. This risk may occur early in treatment and may increase with duration of use. Naproxen is contraindicated in the setting of coronary artery bypass graft (CABG) surgery. 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 patients and patients with a prior history of peptic ulcer disease and/or GI bleeding are at greater risk.
| 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 the setting of coronary artery bypass graft (CABG) surgery; advanced renal disease; history of GI bleeding or perforation related to previous NSAID therapy.
| Precautions | Cardiovascular thrombotic events; gastrointestinal bleeding, ulceration, and perforation; renal toxicity; elevation of liver enzymes; anaphylactoid reactions; serious skin reactions; hypertension; fluid retention; use with aspirin or other NSAIDs increases risk; use in late pregnancy should be avoided. |
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| Fetal Monitoring |
| Monitor for uterine activity, fetal heart rate, amniotic fluid volume (ultrasound if oligohydramnios suspected), and neonatal renal function if used near term. |
| Fertility Effects | Naproxen may impair female fertility through inhibition of prostaglandin synthesis, potentially delaying or preventing ovulation. Reversible upon discontinuation. |
| Food/Dietary | Avoid alcohol. May be taken with food or milk to reduce GI irritation. No specific food restrictions, but avoid high-tyramine foods if also taking MAOIs (though not a common interaction). |
| Clinical Pearls | ANAPROX DS (naproxen sodium) is a nonsteroidal anti-inflammatory drug (NSAID) with rapid absorption; peak plasma levels reached in 1-2 hours. Use with caution in patients with cardiovascular disease or risk factors due to increased risk of thrombotic events. Monitor renal function in elderly, dehydrated, or those on diuretics. Avoid use in patients with severe hepatic impairment. Contraindicated in setting of coronary artery bypass graft (CABG) surgery. For acute pain, use lowest effective dose for shortest duration. May mask signs of infection. |
| Patient Advice | Take with food or milk to reduce gastrointestinal discomfort. · Do not take with other NSAIDs or aspirin unless directed by a doctor. · Report signs of GI bleeding (black/tarry stools, vomit that looks like coffee grounds), chest pain, shortness of breath, or unexplained weight gain. · Avoid alcohol while taking this medication to reduce stomach bleeding risk. · If you have high blood pressure, monitor regularly as this drug may increase it. · Do not use if you are pregnant, especially in third trimester. · May cause dizziness or drowsiness; avoid driving until you know how you react. |