Singapore Drugs Database

Indication

For symptomatic treatment of rheumatoid arthritis, juvenile rheumatoid arthritis and osteoarthritis. May be used to treat mild to moderate pain and for the management of dysmenorrhea. May be used to reduce fever. Has been used with some success for treating ankylosing spondylitis, gout and psoriatic arthritis. May reduce pain, fever and inflammation of pericarditis. May be used IV with opiates to relieve moderate to severe pain. Ibuprofen lysine may be used IV to treat patent ductus arteriosus (PDA) in premature neonates.

Mechanism of Action

The exact mechanism of action of ibuprofen is unknown. Ibuprofen is a non-selective inhibitor of cyclooxygenase, an enzyme invovled in prostaglandin synthesis via the arachidonic acid pathway. Its pharmacological effects are believed to be due to inhibition cylooxygenase-2 (COX-2) which decreases the synthesis of prostaglandins involved in mediating inflammation, pain, fever and swelling. Antipyretic effects may be due to action on the hypothalamus, resulting in an increased peripheral blood flow, vasodilation, and subsequent heat dissipation. Inhibition of COX-1 is thought to cause some of the side effects of ibuprofen including GI ulceration. Ibuprofen is administered as a racemic mixture. The R-enantiomer undergoes extensive interconversion to the S-enantiomer in vivo. The S-enantiomer is believed to be the more pharmacologically active enantiomer.

Pharmacokinetics

Absorption

~ 80% absorbed from GI tract

Time to reach peak plasma concentration = 47 minutes (suspension), 62 minutes (chewable tablets), 120 minutes (conventional tablets)

Distribution

Metabolism

R-enanatiomer undergoes extensive enantiomeric conversion (53-65%) to the more active S-enantiomer in vivo. Metablized by oxidation to 2 inactive metabolites: (+)-2[4´-(2-hydroxy-2-methylpropyl)phenyl]propionic acid and (+)-2-[4´-(2-carboxypropyl)phenyl]propionic acid. Very small amounts of 1-hydroxyibuprofen and 3-hydroxyibuprofen have been recovered from urine. Cytochrome P450 2C9 is the major catalyst in the formation of oxidative metabolites. Oxidative metabolites may be conjugated to glucuronide prior to excretion.

Elimination

Toxicity

Side effects: May cause peripheral edema and fluid retention. Use caution in patients with congestive heart failure or severe uncontrolled hypertension. May cause dyspepsia, heartburn, nausea, vomiting, anorexia, diarrhea, constipation, stomatitis, flatulence, bloating, epigastric pain, and abdominal pain. Peptic ulcer and GI bleeding have been reported. May also cause dizziness, headache and nervousness. Acute renal failure accompanied by acute tubular necrosis has been reported.

Most common symptoms of overdose are abdominal pain, nausea, vomiting, lethargy, vertigo, drowsiness (somnolence), dizziness and insomnia. Other symptoms of overdose include headache, loss of consciousness, tinnitus, CNS depression, convulsions and seizures. May rarely cause metabolic acidosis, abnormal hepatic function, hyperkalemia, renal failure, dyspnea, respiratory depression, coma, acute renal failure, and apnea (primarily in very young pediatric patients).

LD₅₀=1255mg/kg(orally in mice)

Active Ingredient/Synonyms

(±)-2-(p-isobutylphenyl)propionic acid | (±)-ibuprofen | (±)-p-isobutylhydratropic acid | (±)-α-methyl-4-(2-methylpropyl)benzeneacetic acid | (4-isobutylphenyl)-α-methylacetic acid | (RS)-ibuprofen | 2-(4-isobutylphenyl)propanoic acid | 4-isobutylhydratropic acid | Ibuprophen | α-(4-isobutylphenyl)propionic acid | α-(p-isobutylphenyl)propionic acid | Ibuprofen |