RELAFEN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for RELAFEN (RELAFEN).
Nabumetone is a nonacidic nonsteroidal anti-inflammatory drug (NSAID) that is a prodrug, rapidly metabolized to the active metabolite 6-methoxy-2-naphthylacetic acid (6-MNA), which inhibits cyclooxygenase (COX) and thereby prostaglandin synthesis.
| Metabolism | Nabumetone is extensively metabolized in the liver to the active metabolite 6-MNA, primarily via CYP1A2 and to a lesser extent CYP2C9. 6-MNA is further metabolized and conjugated. |
| Excretion | Primarily renal (90% as metabolites, ~5% unchanged); biliary/fecal minor (<5%). |
| Half-life | Terminal elimination half-life approximately 24 hours (range 20-30 hours), allowing once-daily dosing. |
| Protein binding | >99% bound, primarily to albumin. |
| Volume of Distribution | 7-10 L (approximately 0.1-0.15 L/kg), indicating limited extravascular distribution. |
| Bioavailability | Oral: >80% (well absorbed); not administered parenterally. |
| Onset of Action | Oral: 1-2 hours for analgesic effect; 2 weeks for antiarthritic effect. |
| Duration of Action | Analgesic: 6-12 hours; anti-inflammatory: 12-24 hours with chronic dosing. |
1000 mg orally once daily, or 500 mg twice daily. Maximum dose 2000 mg/day.
| Dosage form | TABLET |
| Renal impairment | CrCl 30-49 mL/min: reduce dose by 50%; CrCl <30 mL/min: not recommended. |
| Liver impairment | No specific recommendations; use caution in severe hepatic impairment (Child-Pugh C). |
| Pediatric use | Not approved for children <16 years; safety and efficacy not established. |
| Geriatric use | Reduce starting dose; maximum 1000 mg/day; monitor renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for RELAFEN (RELAFEN).
| Breastfeeding | Nabumetone is excreted into breast milk in small amounts. The M/P ratio is not reported. Use with caution, especially in nursing infants with known NSAID sensitivity. Avoid due to potential adverse effects on infant renal function. |
| Teratogenic Risk | RELAFEN (nabumetone) is a nonsteroidal anti-inflammatory drug (NSAID). Avoid use during first and second trimesters unless benefit outweighs risk; may be associated with oligohydramnios and fetal renal impairment. Contraindicated in third trimester due to risk of premature closure of ductus arteriosus and fetal nephrotoxicity. |
■ FDA Black Box Warning
NSAIDs cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal. This risk may increase with duration of use. Patients with cardiovascular risk factors may be at greater risk. RELAFEN is contraindicated for the treatment of perioperative pain in the setting of coronary artery bypass graft (CABG) surgery.
| Serious Effects |
History of allergic reaction to aspirin or other NSAIDs; perioperative pain in CABG surgery; advanced renal disease; and patients with active gastrointestinal bleed or peptic ulcer disease.
| Precautions | Serious cardiovascular thrombotic events; gastrointestinal bleeding, ulceration, and perforation; hypertension; heart failure and edema; renal toxicity; anaphylactoid reactions; serious skin reactions (e.g., Stevens-Johnson syndrome); hematologic toxicity; hepatic effects; pre-existing asthma; masking of inflammation; and ophthalmic effects. |
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| Fetal Monitoring |
| Monitor fetal ultrasound for oligohydramnios if used during pregnancy. In third trimester, monitor ductus arteriosus flow via fetal echocardiography if exposure occurs. Assess maternal renal function and bleeding time. |
| Fertility Effects | Nabumetone may impair female fertility via inhibition of prostaglandin synthesis, affecting ovulation. Reversible upon discontinuation. Not recommended in women attempting conception. |