Ibuprofen

Medical uses

Ibuprofen is used primarily to treat fever (including postimmunisation fever), mild to moderate pain (including pain relief after surgery), painful menstruation, osteoarthritis, dental pain, headaches, and pain from kidney stones. About 60% of people respond to any NSAID; those who do not respond well to a particular one may respond to another.

It is used for inflammatory diseases such as juvenile idiopathic arthritis and rheumatoid arthritis. It is also used for pericarditis and patent ductus arteriosus.

Ibuprofen lysine

In some countries, ibuprofen lysine (the lysine salt of ibuprofen, sometimes called "ibuprofen lysinate") is licensed for treatment of the same conditions as ibuprofen; the lysine salt is used because it is more water-soluble. In 2006, ibuprofen lysine was approved in the US by the Food and Drug Administration (FDA) for closure of patent ductus arteriosus in premature infants weighing between 500 and 1,500 grams (1 and 3 lb), who are no more than 32 weeks gestational age when usual medical management (such as fluid restriction, diuretics, and respiratory support) is not effective.

Adverse effects

Adverse effects include nausea, dyspepsia, diarrhea, constipation, gastrointestinal ulceration/bleeding, headache, dizziness, rash, salt and fluid retention, and hypertension.

Infrequent adverse effects include esophageal ulceration, heart failure, hyperkalemia, renal impairment, confusion, and bronchospasm. Ibuprofen can exacerbate asthma, sometimes fatally.

Ibuprofen may be quantified in blood, plasma, or serum to demonstrate the presence of the drug in a person having experienced an anaphylactic reaction, confirm a diagnosis of poisoning in hospitalized patients, or assist in a medicolegal death investigation. A monograph relating ibuprofen plasma concentration, time since ingestion, and risk of developing renal toxicity in overdose patients has been published.

Cardiovascular risk

Along with several other NSAIDs, chronic ibuprofen use has been found correlated with risk of hypertension and myocardial infarction (heart attack), particularly among those chronically using high doses. In older hypertensive patients treated with hydrochlorothiazide, ibuprofen at a high daily dose was found to significantly increase systolic blood pressure. On 9 July 2015, the US FDA toughened warnings of increased heart attack and stroke risk associated with ibuprofen and related NSAIDs; the NSAID aspirin is not included in this warning.

Skin

Along with other NSAIDs, ibuprofen has been associated with the onset of bullous pemphigoid or pemphigoid-like blistering. As with other NSAIDs, ibuprofen has been reported to be a photosensitising agent, but it is considered a weak photosensitising agent compared to other members of the 2-arylpropionic acid class. Like other NSAIDs, ibuprofen is an extremely rare cause of the autoimmune disease Stevens–Johnson syndrome (SJS). Ibuprofen is also an extremely rare cause of Lyell's Syndrome (toxic epidermal necrolysis).

Interactions

Drinking alcohol when taking ibuprofen may increase the risk of stomach bleeding.

According to the US Food and Drug Administration (FDA), "ibuprofen can interfere with the antiplatelet effect of low-dose aspirin, potentially rendering aspirin less effective when used for cardioprotection and stroke prevention." Allowing sufficient time between doses of ibuprofen and immediate-release (IR) aspirin can avoid this problem. The recommended elapsed time between a dose of ibuprofen and a dose of aspirin depends on which is taken first. It would be 30 minutes or more for ibuprofen taken after IR aspirin, and eight hours or more for ibuprofen taken before IR aspirin. However, this timing cannot be recommended for enteric-coated aspirin. But, if ibuprofen is taken only occasionally without the recommended timing, the reduction of the cardioprotection and stroke prevention of a daily aspirin regimen is minimal.

Overdose

Ibuprofen overdose has become common since it was licensed for OTC use. Many overdose experiences are 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 despite 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.

Correlation between severity of symptoms and measured ibuprofen plasma levels is weak. Toxic effects are unlikely at doses below 100 mg/kg, but can be severe above 400 mg/kg (around 150 tablets of 200 mg units for an average man); however, large doses do not indicate the clinical course is likely to be lethal. A precise lethal dose is difficult to determine, as it may vary with age, weight, and concomitant conditions of the individual person.

Therapy is largely symptomatic. In cases presenting early, gastric decontamination is recommended. This is achieved using activated charcoal; charcoal adsorbs 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. Since ibuprofen has acidic properties and is also excreted in the urine, forced alkaline diuresis is theoretically beneficial. However, because ibuprofen is highly protein-bound in the blood, renal excretion of unchanged drug is minimal. Forced alkaline diuresis is, therefore, of limited benefit. Symptomatic therapy for hypotension, gastrointestinal bleeding, acidosis, and renal toxicity may be indicated. On occasion, close monitoring in an intensive-care unit for several days is necessary. A patient who survives the acute intoxication usually experiences no late sequelae.

Miscarriage

A study of pregnant women suggests those taking any type or amount of NSAIDs (including ibuprofen, diclofenac and naproxen) were 2.4 times more likely to miscarry than those not taking the drugs. However, an Israeli study found no increased risk of miscarriage in the group of mothers using NSAIDs.

Mechanism of action

Nonsteroidal anti-inflammatory drugs such as ibuprofen work by inhibiting the cyclooxygenase (COX) enzymes, which convert 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 and indometacin, ibuprofen is a nonselective COX inhibitor, in that it inhibits two isoforms of cyclooxygenase, COX-1 and COX-2. The analgesic, antipyretic, and anti-inflammatory activity of NSAIDs appears to operate mainly through inhibition of 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 instead would be responsible for unwanted effects on 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.

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. The R-enantiomer is converted through a series of three main enzymes. These enzymes include acyl-CoA-synthetase, which converts the R-enantiomer to (-)-R-ibuprofen I-CoA; 2-arylpropionyl-CoA epimerase, which converts (-)-R-ibuprofen I-CoA to (+)-S-Ibuprofen I-CoA; and hydrolase, which converts (+)-S-ibuprofen I-CoA to the S-enantiomer. In addition to the conversion of ibuprofen to the S-enantiomer, the body can metabolize ibuprofen to several other compounds, including numerous hydroxyl, carboxyl and glucuronyl metabolites. Virtually all of these have no pharmacological effects.

Chemistry

Ibuprofen is practically insoluble in water, but very soluble in most organic solvents (ethanol, methanol, acetone and dichloromethane).

The original synthesis of ibuprofen by the Boots Group started with the compound 2-methylpropylbenzene. The synthesis took six steps. A modern, greener technique for the synthesis involves only three steps.

Stereochemistry

It is an optically active compound with both S and R-isomers, of which the S (dextrorotatory) isomer is the more biologically active; this isomer has also been isolated and used medically (see dexibuprofen for details).

Ibuprofen is produced industrially as a racemate. The compound, like other 2-arylpropionate derivatives (including ketoprofen, flurbiprofen, naproxen, etc.), does contain a chiral center in the α-position of the propionate moiety. So two enantiomers of ibuprofen occur, with the potential for different biological effects and metabolism for each enantiomer. Indeed, the (S)-(+)-ibuprofen (dexibuprofen) was found to be the active form both in vitro and in vivo.

An isomerase (alpha-methylacyl-CoA racemase) converts (R)-ibuprofen to the active (S)-enantiomer.

History

Ibuprofen was derived from propionic acid by the research arm of Boots Group during the 1960s. Its discovery was the result of research during the 1950s and 1960s to find a safer alternative to aspirin. It was discovered by a team led by Stewart Adams and the patent application was filed in 1961. Adams initially tested the drug as treatment for his hangover. The drug was launched as a treatment for rheumatoid arthritis in the United Kingdom in 1969, and in the United States in 1974. Later, in 1983 and 1984, it became the first NSAID (other than aspirin) to be available over the counter (OTC) in these two countries. Dr. Adams 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.

Marketing

Ibuprofen was made available under prescription in the United Kingdom in 1969, and in the United States in 1974. In the years since, the good tolerability profile, along with extensive experience in the population, as well as in so-called phase-IV trials (postapproval studies), have resulted in the availability of ibuprofen OTC in pharmacies worldwide, as well as in supermarkets and other general retailers. Ibuprofen is its INN, BAN, AAN and USAN approved name. Advil is manufactured by Pfizer and has been on the market since 1984.

North America

Ibuprofen is commonly available in the United States up to the FDA's 1984 dose limit OTC, rarely used higher by prescription. In 2009, the first injectable formulation of ibuprofen was approved in the United States, under the trade name Caldolor.

Research

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 with a placebo in the prevention of Alzheimer's disease, when given in low doses over a long time.

Ibuprofen has been associated with a lower risk of Parkinson's disease, and may delay or prevent it. Aspirin, other NSAIDs, and paracetamol (acetaminophen) had no effect on the risk for Parkinson's. In March 2011, researchers at Harvard Medical School announced in Neurology that ibuprofen had a neuroprotective effect against the risk of developing Parkinson's disease. People regularly consuming ibuprofen were reported to have a 38% lower risk of developing Parkinson's disease, but no such effect was found for other pain relievers, such as aspirin and paracetamol. Use of ibuprofen to lower the risk of Parkinson's disease in the general population would not be problem-free, given the possibility of adverse effects on the urinary and digestive systems.

Some dietary supplements might be dangerous to take along with ibuprofen and other NSAIDs, but as of 2016 more research needs to be conducted to be certain. These supplements include those that can prevent antiplatelet aggregation, including ginkgo, garlic, ginger, bilberry, dong quai, feverfew, ginseng, turmeric, meadowsweet and willow), those that contain coumarin, including chamomile, horse chestnut, fenugreek and red clover, and those that increase the risk of bleeding, like tamarind.