Ibuprofen is a propionic acid derivative and a nonsteroidal anti-inflammatory drug (NSAID). It is used to relieve pain, reduce fever, and treat inflammatory conditions such as arthritis and menstrual cramps. It is sold both as a prescription medicine and over the counter in many countries. Chemically, it is 2-(4-isobutylphenyl)propanoic acid, and the racemic drug is sold as a mixture of two enantiomers. Its main pharmacological action is the inhibition of cyclooxygenase (COX) enzymes, which reduces the production of prostaglandins. Ibuprofen is listed on the World Health Organization's Model List of Essential Medicines.
History
Ibuprofen was developed in the 1950s and 1960s at the Boots Pure Drug Company in Nottingham, England. Pharmacologist Stewart Adams and chemist John Nicholson led the work. Their goal was to find an analgesic that was safer and better tolerated than aspirin for patients with rheumatoid arthritis. The team screened a large number of compounds, and the propionic acid derivative later named ibuprofen was among those tested. Sources differ on the exact dates. Some give 1961 as the year of discovery and patenting, while the U.S. patent is often cited as 1966 and the U.S. Hall of Fame summary of the work notes the patent for the pair was issued that year. The drug was first marketed in the United Kingdom under the name Brufen, and it reached the United States in 1974 under the name Motrin, sold by Upjohn.
An earlier Boots compound, ibufenac, was withdrawn in 1968 because of liver toxicity, which shaped the later search for safer candidates. Ibuprofen was developed before the role of prostaglandins in inflammation was established in the early 1970s, so no defined biochemical target guided its discovery. Its non-prescription sale in the United Kingdom began in 1983, after an earlier application to sell it in general pharmacies was declined by the regulator.
Pharmacology
Mechanism of action
Ibuprofen is a non-selective, reversible inhibitor of both COX-1 and COX-2. These enzymes convert arachidonic acid into prostaglandin H2, the precursor of several prostanoids, including prostaglandins E2, D2 and F2α, prostacyclin, and thromboxane A2. The anti-inflammatory, analgesic, and antipyretic effects are thought to arise mainly from the suppression of COX-2 activity in inflamed tissue. The inhibition of COX-1 is linked to the drug's effects on platelets and the gastric lining. Some in-vitro work reports that ibuprofen also suppresses transcription factors such as NF-κB and AP-1, which may contribute to its anti-inflammatory action, although the clinical significance of this is less clear.
The drug is a racemate. The S-enantiomer is the more potent COX inhibitor, while the R-enantiomer is considerably weaker, and a portion of the R form is converted to the active S form in the body. This inversion is a notable feature of the drug's metabolism.
Pharmacokinetics
Ibuprofen is absorbed quickly after oral administration and is mostly bound to plasma proteins. It is metabolized in the liver, and its metabolites are mainly excreted in urine. Its elimination half-life is short, about two to four hours, which is why it is usually taken several times a day to maintain analgesia.
Platelet effects
Because the inhibition of COX-1 in platelets is reversible and short-lived, ibuprofen's antiplatelet effect is weaker and briefer than that of aspirin. Aspirin acts by irreversibly acetylating COX, and ibuprofen can interfere with this action when the two are taken together, which is a practical concern for patients on low-dose aspirin for cardioprotection.
Medical uses
Ibuprofen is used for mild to moderate pain, including headache, dental pain, musculoskeletal injuries, and postoperative pain. It is also used for primary dysmenorrhea and for the symptomatic treatment of fever. In rheumatology, it is used to treat osteoarthritis, rheumatoid arthritis, and other inflammatory conditions. In neonatology, it is used to close a patent ductus arteriosus in premature infants, where it is an alternative to indomethacin. Its use in such contexts is typically decided by physicians.
Ibuprofen is often combined with other analgesics, such as paracetamol (acetaminophen), because the two act through different mechanisms. Clinical studies of combinations have been published, but the optimal combination and dosing depend on the clinical setting.
Adverse effects and safety
Gastrointestinal effects
The most common adverse effects of ibuprofen are gastrointestinal, including nausea, dyspepsia, abdominal pain, diarrhea or constipation, and bloating. More serious complications, such as bleeding, ulceration, and perforation of the stomach or intestine, can occur at any time during treatment and may come without warning symptoms. Inhibition of COX-1 is considered the main cause of this damage, because it lowers the mucosal prostaglandins that protect the gastric lining and reduces mucus and bicarbonate secretion. Risk increases with higher doses, longer use, older age, and a history of peptic ulcer disease. Concomitant use of corticosteroids or anticoagulants further raises the risk. Among the non-selective NSAIDs, ibuprofen is often described as having a comparatively low rate of gastrointestinal events at low doses, although it is not free of such risk.
Cardiovascular effects
Regulators in several countries have warned that NSAIDs, including ibuprofen, may increase the risk of heart attack and stroke. The risk appears in some analyses to rise with dose and duration and is greater in people with existing cardiovascular disease or risk factors such as hypertension, hyperlipidemia, diabetes, and smoking. A 2015 New Zealand review concluded that the increase is small and most evident with high doses (about 2400 mg per day) and long-term treatment, while standard over-the-counter doses of up to 1200 mg per day were not associated with the same increase. The United States Food and Drug Administration has required a boxed warning on all prescription NSAIDs regarding cardiovascular and gastrointestinal risk. The mechanism is thought to involve an imbalance between prostacyclin and thromboxane. Because all NSAIDs share this class effect, it is difficult to distinguish the risk of one from another.
Renal, hepatic, and hematologic effects
Long-term or high-dose use can impair kidney function, particularly in people with pre-existing kidney disease, dehydration, or heart failure, and it can cause fluid retention and edema. Hepatotoxicity is less common but has been reported. Hematologic effects include the transient inhibition of platelet function described above. Allergic reactions range from mild rash to rare severe cutaneous reactions and asthma exacerbations, particularly in people sensitive to aspirin or other NSAIDs.
Special populations
Use of NSAIDs in late pregnancy is generally avoided because of the risk of fetal ductus arteriosus constriction, and guidance on use in early and mid-pregnancy varies by country. Older adults are more vulnerable to gastrointestinal and renal complications. Children are dosed by weight, and the medicine is widely used in pediatric pain and fever.
Formulations and availability
Ibuprofen is available as oral tablets, capsules, liquid suspensions, chewable forms, and injectable solutions for intravenous use in hospitals. Topical preparations are also marketed. Dosing differs between prescription and over-the-counter products, and the lower dose range is generally regarded as having a more favorable safety profile.
Regulation and controversies
Ibuprofen's transition from prescription to over-the-counter status occurred in many countries during the 1980s and 1990s, and its broad availability has made it one of the most widely used medicines worldwide. Debate continues over the relative cardiovascular and gastrointestinal risks of NSAIDs, the appropriate dose thresholds for labeling, and the extent to which the risks are dose-dependent. Regulators have issued revised warnings over the years, and the balance of benefit and harm is assessed differently across agencies. Some researchers have also examined ibuprofen's potential effects beyond analgesia, such as in cancer and neurodegenerative disease, but these lines of research have not led to approved uses.
See also
References
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