Ibuprofen

What is Ibuprofen?

Ibuprofen (INN) ( or ; from the now outdated nomenclature iso-butyl-propanoic-phenolic acid) is a non-steroidal anti-inflammatory drug (NSAID) originally marketed as Brufen, and since then under various other trademarks (see tradenames section), most notably Nurofen, Advil and Motrin. It is used for relief of symptoms of arthritis, primary dysmenorrhea, fever, and as an analgesic, especially where there is an inflammatory component. Ibuprofen is known to have an antiplatelet effect, though it is relatively mild and short-lived when compared with that of aspirin or other better-known antiplatelet drugs. Ibuprofen is a ''core'' medicine in the World Health Organization's "Essential Drugs List", which is a list of minimum medical needs for a basic health care system.

Ibuprofen was derived from propionic acid by the research arm of Boots Group during the 1960s. It was discovered by Andrew RM Dunlop, with colleagues Stewart Adams, John Nicholson, Jeff Wilson & Colin Burrows and was patented in 1961. The drug was launched as a treatment for rheumatoid arthritis in the United Kingdom in 1969, and in the United States in 1974. Dr. Adams initially tested his drug on a hangover. He was subsequently awarded an OBE in 1987. Boots was awarded the Queen's Award For Technical Achievement for the development of the drug in 1987.

On 15 January 2010, Johnson & Johnson announced the recall of several hundred batches of popular medicines, including Benadryl, Motrin, Rolaids, Simply Sleep, St. Joseph Aspirin and Tylenol. The recall was due to contamination with the chemical 2,4,6-tribromoanisole. The full health effects of 2,4,6-tribromoanisole are not known. The recall came 20 months after McNeil first began receiving consumer complaints about moldy-smelling bottles of Tylenol Arthritis Relief caplets, according to a warning letter sent by the Food and Drug Administration.

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Ibuprofen Chemistry

Ibuprofen is only very slightly soluble in water, less than 1 mg of ibuprofen dissolves in 1 ml water (< 1 mg/mL). However, it is much more soluble in alcohol/water mixtures.

Stereochemistry

Ibuprofen, like other 2-arylpropionate derivatives (including ketoprofen, flurbiprofen, naproxen, ''etc''), contains a stereocenter in the α-position of the propionate moiety. As such, there are two possible enantiomers of ibuprofen, with the potential for different biological effects and metabolism for each enantiomer.

Indeed it was found that (''S'')-(+)-ibuprofen (dexibuprofen) was the active form both ''in vitro'' and ''in vivo''.

It was logical, then, that there was the potential for improving the selectivity and potency of ibuprofen formulations by marketing ibuprofen as a single-enantiomer product (as occurs with naproxen, another NSAID).

Further ''in vivo'' testing, however, revealed the existence of an isomerase (''2-arylpropionyl-CoA epimerase'') which converted (''R'')-ibuprofen to the active (''S'')-enantiomer. Thus, due to the expense and futility that might be involved in making a pure enantiomer, most ibuprofen formulations currently marketed are racemic mixtures.

Synthesis

The synthesis of this compound is a popular case study in green chemistry. The original Boots synthesis of ibuprofen consisted of six steps, started with the Friedel-Crafts acetylation of isobutylbenzene. Reaction with ethyl chloroacetate (Darzens reaction) gave the α,β-epoxy ester, which was decarboxylated and hydrolyzed to the aldehyde. Reaction with hydroxylamine gave the oxime, converted to the nitrile, then hydrolyzed to the desired acid.

An improved synthesis by BHC required only three steps. This improved synthesis won the Presidential Green Chemistry Challenge Greener Synthetic Pathways Award in 1997.

After a similar acetylation, hydrogenation with Raney nickel gave the alcohol, which underwent palladium-catalyzed carbonylation:

Europe

For some time, there has been a limit on the amount that can be bought over the counter in a single transaction in the UK. Behind the counter in pharmacies this is one pack of 96 × 200 mg or 400 mg, the latter being far less common for over the counter sales. In UK non-pharmacy outlets only 200 mg tablets are allowed and they are restricted to a maximum pack of 16 tablets.

In Germany, 600 mg and 800 mg per pill packages have to be prescribed, whereas 400 mg is available over the counter in pharmacies. In Italy, Belgium and the Netherlands, 200 mg and 400 mg pills are available with no prescription.

In other countries, higher dosages of 600 mg are available.

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Ibuprofen Dosage

Low doses of ibuprofen (200 mg, and sometimes 400 mg) are available over the counter (OTC) in most countries. Ibuprofen has a dose-dependent duration of action of approximately 4–8 hours, which is longer than suggested by its short half-life. The recommended dose varies with body mass and indication. Generally, the oral dose is 200–400 mg (5–10 mg/kg in children) every 4–6 hours, adding up to a usual daily dose of 800–1,200 mg. 1,200 mg is considered the maximum daily dose for over-the-counter use, though under medical direction, the maximum amount of ibuprofen for adults is 800 milligrams per dose or 3200 mg per day (4 maximum doses).

Unlike aspirin, which breaks down in solution, ibuprofen is stable, and thus ibuprofen can be available in topical gel form which is absorbed through the skin, and can be used for sports injuries, with less risk of gastrointestinal problems.

Off-label and investigational use

Ibuprofen is sometimes used for the treatment of acne, because of its anti-inflammatory properties, and has been sold in Japan in topical form for adult acne.

As with other NSAIDs, ibuprofen may be useful in the treatment of severe orthostatic hypotension (low blood pressure when standing up).

In some studies, ibuprofen showed superior results compared to a placebo in the prophylaxis of Alzheimer's disease, when given in low doses over a long time. Further studies are needed to confirm the results before ibuprofen can be recommended for this indication.

Ibuprofen has been associated with a lower risk of Parkinson's disease, and may delay or prevent it. Aspirin, other NSAIDs, and paracetamol had no effect on the risk for Parkinson's. Further research is warranted before recommending ibuprofen for this use.

Ibuprofen lysine

In Europe, Australia, and New Zealand, ibuprofen lysine (the lysine salt of ibuprofen, sometimes called "ibuprofen lysinate" even though the lysine is in cationic form) is licensed for treatment of the same conditions as ibuprofen. The lysine salt increases water solubility, allowing the medication to be administered intravenously. Ibuprofen lysine has been shown to have a more rapid onset of action compared to acid ibuprofen.

Ibuprofen lysine is indicated for closure of a patent ductus arteriosus in premature infants weighing between 500 and 1500 grams, who are no more than 32 weeks gestational age when usual medical management (e.g., fluid restriction, diuretics, respiratory support, etc.) is ineffective.

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Ibuprofen Mechanism

Non-steroidal anti-inflammatory drugs such as ibuprofen work by inhibiting the enzyme cyclooxygenase (COX), which converts arachidonic acid to prostaglandin H2 (PGH2). PGH2, in turn, is converted by other enzymes to several other prostaglandins (which are mediators of pain, inflammation, and fever) and to thromboxane A2 (which stimulates platelet aggregation, leading to the formation of blood clots).

Like aspirin, indomethacin, and most other NSAIDs, ibuprofen is considered a non-selective COX inhibitor—that is, it inhibits two isoforms of cyclooxygenase, ''COX-1'' and ''COX-2''. The analgesic, antipyretic, and anti-inflammatory activity of NSAIDs appears to be achieved mainly through inhibition of COX-2, whereas inhibition of COX-1 would be responsible for unwanted effects on platelet aggregation and the gastrointestinal tract. However, the role of the individual COX isoforms in the analgesic, anti-inflammatory, and gastric damage effects of NSAIDs is uncertain and different compounds cause different degrees of analgesia and gastric damage.

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Ibuprofen Side Effects

Ibuprofen appears to have the lowest incidence of gastrointestinal adverse drug reactions (ADRs) of all the non-selective NSAIDs. However, this only holds true at lower doses of ibuprofen, so over-the-counter preparations of ibuprofen are generally labeled to advise a maximum daily dose of 1,200 mg.

Common adverse effects include: nausea, dyspepsia, gastrointestinal ulceration/bleeding, raised liver enzymes, diarrhea, constipation, epistaxis, headache, dizziness, priapism, rash, salt and fluid retention, and hypertension.

Infrequent adverse effects include: esophageal ulceration, heart failure, hyperkalemia, renal impairment, confusion, and bronchospasm. However, this only rarely occurs with ibuprofen and it is considered to be a very weak photosensitising agent when compared with other members of the 2-arylpropionic acid class. This is because the ibuprofen molecule contains only a single phenyl moiety and no bond conjugation, resulting in a very weak chromophore system and a very weak absorption spectrum which does not reach into the solar spectrum.

Cardiovascular risk

Along with several other NSAIDs, ibuprofen has been implicated in elevating the risk of myocardial infarction (heart attack), particularly among those chronically using high doses.

Risks in inflammatory bowel disease (IBD)

Ibuprofen should not be used regularly in individuals with inflammatory bowel disease due to its ability to cause gastric bleeding and form ulceration in the gastric lining. Pain relievers such as paracetemol/acetaminophen or drugs containing codeine (which slows down bowel activity) are safer methods than ibuprofen for pain relief in IBD. Ibuprofen is also known to cause worsening of IBD during times of a flare-up, thus should be avoided completely.

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Ibuprofen Toxicology

Ibuprofen overdose has become common since it was licensed for over-the-counter use. There are many overdose experiences reported in the medical literature, although the frequency of life-threatening complications from ibuprofen overdose is low. Human response in cases of overdose ranges from absence of symptoms to fatal outcome in spite of intensive care treatment.

Most symptoms are an excess of the pharmacological action of ibuprofen and include abdominal pain, nausea, vomiting, drowsiness, dizziness, headache, tinnitus, and nystagmus. Rarely more severe symptoms such as gastrointestinal bleeding, seizures, metabolic acidosis, hyperkalaemia, hypotension, bradycardia, tachycardia, atrial fibrillation, coma, hepatic dysfunction, acute renal failure, cyanosis, respiratory depression, and cardiac arrest have been reported. The severity of symptoms varies with the ingested dose and the time elapsed; however, individual sensitivity also plays an important role. Generally, the symptoms observed with an overdose of ibuprofen are similar to the symptoms caused by overdoses of other NSAIDs.

There is little correlation between severity of symptoms and measured ibuprofen plasma levels. Toxic effects are unlikely at doses below 100 mg/kg but can be severe above 400 mg/kg; (around 150 200mg tablets for an average man) however, large doses do not indicate that the clinical course is likely to be lethal. It is not possible to determine a precise lethal dose, as this may vary with age, weight, and concomitant diseases of the individual patient.

Therapy is largely symptomatic. In cases presenting early, gastric decontamination is recommended. This is achieved using activated charcoal; charcoal absorbs the drug before it can enter the systemic circulation. Gastric lavage is now rarely used, but can be considered if the amount ingested is potentially life threatening and it can be performed within 60 minutes of ingestion. Emesis is not recommended. The majority of ibuprofen ingestions produce only mild effects and the management of overdose is straightforward. Standard measures to maintain normal urine output should be instituted and renal function monitored. Symptomatic therapy for hypotension, GI bleeding, acidosis, and renal toxicity may be indicated. Occasionally, close monitoring in an intensive care unit for several days is necessary. If a patient survives the acute intoxication, they will usually experience no late sequelae.

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