Clinical use

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, up to a usual maximum daily dose of 800–1200 mg. Under medical direction, a maximum daily dose of 3200 mg may sometimes be used.

Off-Label and investigational use

   * As with other NSAIDs, ibuprofen may be useful in the treatment of severe orthostatic hypotension.
   * In some studies, ibuprofen showed superior results compared to 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 Parkinson's disease. 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 (ibuprofenlysinat, the lysine salt of ibuprofen) is licensed for treatment of the same conditions as ibuprofen. Ibuprofen lysine has been shown to have a more rapid onset of action compared to base ibuprofen.

Mechanism of action

Ibuprofen is an NSAID which is believed to work through inhibition of cyclooxygenase (COX), thus inhibiting prostaglandin synthesis. There are at least 2 variations of cyclooxygenase (COX-1 and COX-2), ibuprofen inhibits both COX-1 and COX-2. It appears that its analgesic, antipyretic, and anti-inflammatory activity are achieved principally through COX-2 inhibition; whereas COX-1 inhibition is responsible for its unwanted effects on platelet aggregation and the GI mucosa.

Adverse 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 labelled to advise a maximum daily dose of 1,200 mg.

Reported adverse drug reactions

In low single doses (200 to 400 mg) and daily doses of up to 1,200 mg the incidence of side effects is low. However, in patients treated on a long-term basis with more than 1,200 mg daily discontinuation rates are as high as 10 to 15%.

Common adverse effects include: nausea, dyspepsia, gastrointestinal ulceration/bleeding, raised liver enzymes, diarrhoea, headache, dizziness, salt and fluid retention, hypertension.

Infrequent adverse effects include: oesophageal ulceration, heart failure, hyperkalaemia, renal impairment, confusion, bronchospasm, rash.

Photosensitivity

As with other NSAIDs, ibuprofen has been reported to be a photosensitising agent. 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 acids. 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, particularly among those chronically using high doses.

Stereochemistry

Ibuprofen, like other 2-arylpropionate derivatives (including ketoprofen, flurbiprofen, naproxen, etc) contains a chiral carbon 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 which converted (R)-ibuprofen to the active (S)-enantiomer. Thus, due to the expense and futility that might be involved in marketing the single-enantiomer, most ibuprofen formulations currently marketed are racemic mixtures. A notable exception to this is Seractiv (Nordic Drugs).

Human 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. 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; 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. Since ibuprofen has acidic properties and is also excreted in the urine, forced alkaline diuresis is theoretically beneficial. However, due to the fact ibuprofen is highly protein bound in the blood, there is minimal renal excretion of unchanged drug. Forced alkaline diuresis is therefore of limited benefit. 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, he/she will usually experience no late sequelae.

Availability

Ibuprofen was made available under prescription in the United Kingdom in 1969. In the years since, the good tolerability profile along with extensive experience in the community (otherwise known as Phase IV trials), has resulted in the rescheduling of small packs of ibuprofen to allow availability over-the-counter in pharmacies worldwide. Indeed there has been an increasing trend towards descheduling ibuprofen such that it is now available in supermarkets and other general retailers. The wider availability has meant that ibuprofen is now almost as commonly used as aspirin and paracetamol.