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Diflunisal: Wikis


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Systematic (IUPAC) name
2',4'-difluoro-4-hydroxybiphenyl-3-carboxylic acid
CAS number 22494-42-4
ATC code N02BA11
PubChem 3059
DrugBank APRD00922
ChemSpider 2951
Chemical data
Formula C 13H8F2O3  
Mol. mass 250.198 g/mol
SMILES eMolecules & PubChem
Pharmacokinetic data
Bioavailability 80-90%
Protein binding >99%
Metabolism Hepatic
Half life 8 to 12 hours
Excretion Renal
Therapeutic considerations
Pregnancy cat. C(AU) C(US)
Legal status POM (UK) -only (US)
Routes Oral
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'Diflunisal' is a generic NSAID (non-steroidal anti-inflammatory drug). It was developed by Merck Sharp & Dohme in 1971 after showing promise in a research project studying more potent chemical analogs of aspirin.[1] It was first sold under the brand name Dolobid, marketed by Merck & Co., but generic versions are now widely available. It is available in 250 mg and 500 mg tablets.



Like all NSAIDs, Diflunisal acts by inhibiting the production of prostaglandin [2], a hormone which is involved in inflammation and pain. There is also an antipyretic effect, but this is not a recommended use of the drug. Though diflunisal has an onset of 1 hour, and maximum analgesia at 2 to 3 hours, the diflunisal plasma levels will not be steady until repeated doesages are achieved. The long plasma half-life is a distinctive feature of diflunisal in comparison to similar drugs. To increase the rate at which the diflunisal plasma levels become steady, a loading dose is usually used. It is primarily used to treat symptoms of arthritis, and for acute pain following oral surgery, especially removal of wisdom teeth.

Side Effects

The inhibition of prostaglandins also has the effect of decreasing the protection given to the stomach from its own acid. Like all NSAIDS, this leads to an increased risk of stomach ulcers, and their complications, with long-term use.


Deaths that have occurred from diflunisal usually involved mixed drugs and or extremely high dosage. The oral LD50 is 500 mg/kg. Symptoms of overdose include coma, tachycardia, stupor, and vomiting. The lowest dose without the presence of other medicines which caused death was 15 grams. Mixed with other medicines, a death at 7.5 grams has also occurred. Diflunisal usually comes in 250 or 500 mg, thus it is relatively hard to overdose by accident.


This medication is unlikely to be abused: it has no effects in common with recreational drugs. However, a few people with psychological disturbances are susceptible to abusing medication of any kind.

Indicated for:
  • Pain, mild-moderate
  • Osteoarthritis
  • Rheumatoid arthritis
  • Injury to tendons
  • Inflammation

Do not cut/crush/chew. Monitor blood pressure. Use lowest effective dose for shortest duration.

Side effects:


  • Irregular heart beat (!)
  • This medication may increase risk of serious and potentially fatal cardiovascular thrombotic events, MI, and stroke (!)
  • Risk may increase with duration of use (!)
  • Increased risk for Cardiovascular disease history (!)
  • Contraindicated for Heart Bypass peri-op pain (!)

Ear, nose, and throat:

  • Ringing in the ears (!)


  • Yellowing of eyes (!)


  • Increased risk of serious GI adverse events including bleeding, ulceration, and stomach or intestine perforation which can be fatal: may occur at any time during use and without warning. Elderly at greater risk for serious GI events (!)
  • Abdominal pain and cramps
  • Constipation
  • Gas & Flatulence
  • Diarrhea
  • Nausea & Vomiting
  • Dyspepsia

Central Nervous System:

  • Drowsiness
  • Dizziness
  • Headache
  • Insomnia
  • Fatigue
  • Somnolence


  • Nervousness


  • Swelling of the feet, ankles, lower legs, and hands (!)
  • Yellowing of skin (!)
  • Rash
  • Ecchymosis


  • Hypersensitivity to aspirin/NSAID-induced asthma or urticaria
  • Aspirin triad
  • Pregnancy 3rd trimester
  • CABG surgery (peri-op pain)


  • Cardiovascular disease
  • Cardiac risk factors
  • Hypertension
  • Congestive Heart Failure
  • Elderly or debilitated
  • Impaired liver function
  • Impaired kidney function
  • Dehydration
  • Fluid retention
  • GI bleed history/PUD
  • Asthma
  • Coagulopathy
  • Smoker
  • Corticosteriod use
  • Anticoagulant use
  • Alcohol use
  • Diuretic use
  • ACE Inhibitor use
  • Prolonged use


  • If symptoms labeled, (!), appear, stop usage immediately and contact your doctor.
  • Overdose is possible and deaths have occurred.
  • Do not take while on other pain medications.
  • Do not take while pregnant or breast feeding.


  1. ^ Ibuprofen, the propionics and NSAIDs: Personal reflections over four decades Inflammopharmacology, Volume 7, Number 3 / September, 1999 url= retrieved Aug 12, 2009 doi:10.1007/s10787-999-0002-3
  2. ^ Physiol. Rev. 88: 1547-1565, 2008; doi:10.1152/physrev.00004.2008

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