Nabumetone is a nonsteroidal anti-inflammatory drug (NSAID) of the arylalkanoic acid family (which includes diclofenac). Marketed under the brand name Relafen, it has been shown to have a slightly lower risk of gastrointestinal side effects than most other non-selective NSAIDs.
Indication
For acute and chronic treatment of signs and symptoms of osteoarthritis and rheumatoid arthritis.
Pharmacology
Nabumetone is a naphthylalkanone. Is is a non-selective prostaglandin G/H synthase (a.k.a. cyclooxygenase or COX) inhibitor that acts on both prostaglandin G/H synthase 1 and 2 (COX-1 and -2). Prostaglandin G/H synthase catalyzes the conversion of arachidonic acid to prostaglandin G2 and prostaglandin G2 to prostaglandin H2. Prostaglandin H2 is the precursor to a number of prostaglandins involved in fever, pain, swelling, inflammation, and platelet aggregation. The parent compound is a prodrug that undergoes hepatic biotransformation to the active compound, 6-methoxy-2-naphthylacetic acid (6MNA). The analgesic, antipyretic and anti-inflammatory effects of NSAIDs occur as a result of decreased prostaglandin synthesis.
Toxicity
The one overdose occurred in a 17-year-old female patient who had a history of abdominal pain and was hospitalized for increased abdominal pain following ingestion of 30 nabumetone tablets (15 grams total). Stools were negative for occult blood and there was no fall in serum hemoglobin concentration. The patient had no other symptoms.
Affected Organisms
Humans and other mammals
Biotransformation
Undergoes rapid biotransformation to the principal active metabolite, 6-methoxy-2-naphthylacetic acid (6MNA). Approximately 35% of a 1000 mg oral dose of nabumetone is converted to 6MNA and 50% is converted into unidentified metabolites which are subsequently excreted in the urine.
Absorption
Well absorbed from the gastrointestinal tract. Coadministration of food increases the rate of absorption and subsequent appearance of 6MNA (the active metabolite) in the plasma but does not affect the extent of conversion of nabumetone into 6MNA.
Half Life
Approximately 23 hours for the active metabolite, 6MNA. Increased in patients with renal insufficiency.
Protein Binding
The active metabolite, 6MNA, is more than 99% bound to plasma proteins.
Elimination
Approximately 35% of a 1000 mg oral dose of nabumetone is converted to 6MNA and 50% is converted into unidentified metabolites which are subsequently excreted in the urine.
A methyl ketone that is 2-butanone in which one of the methyl hydrogens at position 4 is replaced by a 6-methoxy-2-naphthyl group. A prodrug that is converted to the active metabolite, 6-methoxy-2-naphthylacetic acid, following oral administration. It is shown to have a slightly lower risk of gastrointestinal side effects than most other non-steroidal anti-inflammatory drugs.
