Go to a medicine cabinet and select a medicine which is used to treat a human disease and write an essay on the active constituent. You should discuss mode of administration, absorption, elimination and mechanism of action. Today one of the abundantly and safest drug used today for the treatment of inflammation, fever and pain is Ibuprofen. Following the extensive clinical testing and development of Ibuprofen is no doubt one of the successes of the pharmaceutical industry. When safety is concerned Ibuprofen has accomplished this aspect really well, as it has a wide range of tolerance while at the same time providing more effective on a dose-for-weight basis than aspirin and Paracetamol in the treatment of many painful conditions. (Rainsford, 1999, vii).
Over 40 years ago the history of Ibuprofen began, this has been linked in order to understand the concepts of the actions of therapeutic agents used at the time and pathogenesis of inflammatory disease. Dr Stewart Adams who was a pharmacologist in the Research Department of The Boots Pure Drug Company Ltd at Nottingham, UK in 1992 was the principal initiator of this research which lead to the discovery of Ibuprofen. (Rainsford, 1999, 3)
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Ibuprofen (2-(4-isobutylphenyl)propionic acid), physical property is that it exists as a white crystalline, slightly waxy solid with a slight odour and a strong and characteristic taste. (Rainsford, 1999, 55)
Figure 1: The chemical structure of Ibuprofen (Harrison 2002)
Figure 1 represents the chemical structure of Ibuprofen, showing that this molecule exists as the (S)-(+) (dextro) or (R)-(-) (laevo) Isomer. Conventional Ibuprofen occurs as a racemic mixture of the two Isomers. (Rainsford, 1999, 55)
Routes of Administration of Ibuprofen.
There are many different routes of administrating Ibuprofen. These routes include, orally, as an injection (intravenous), via rectal and topical.
Ibuprofen can be taken orally either by coated tablets or liquid, both are taken by mouth and swallowed, not much absorption till reaches the small intestine. Tablets are the most predominate dosage form. The tablets contain the active ingredient ibuprofen, which is the pain killer, it has effects like lowering blood temperature and anti-inflammatory characteristics. The most common, convenient route is self ââ‚¬"administration. (M.D. Avram Goldstein, 1969, 119). The liquid form offers an advantage as 8% of patients find it difficult to swallow tablets, Syrup is also the best form for children. A disadvantage is the taste, ibuprofen can have an unpleasant taste, also it sends a burning sensations down the throat. (K.D. Rainsford, 1999, 64-65)
Ibuprofen can be used via IV when rapid response is required, it goes directly in to the vein, and the effects of drug take place within seconds in many cases. Rectal 5% cream or gel is available.
Mechanism of Action of Ibuprofen.
The non-steroidal anti-inflammatory drug Ibuprofen, works by blocking the production of the hormone responsible for pain and inflammatory reactions, known as prostaglandins.
Ibuprofen and other Anti inflammatory and non steroidal drugs work by the enzyme cyclooxygenase being inhibited; this causes arachidonic acid to convert into prostaglandin H2 (PGH2). Other enzymes then in turn convert PGH2 into several other prostaglandins, (these prostaglandins are mediators of fever, pain and inflammation) and to thromboxane A2 (blood clots are formed due to platelet aggregation being stimulated by thromboxane A2).
Like indomethacin, aspirin and other NSAIDs, Ibuprofen inhibits two isoforms of cyclooxygenase, COX-1 and COX-2 and therefore is considered as a non selective COX inhibitor. The anti-inflammotory, antipyretic and analgesic activity of NSAIDS is mainly achieved through inhibiting COX-2, whereas unwanted effects on platelet aggregation and gastrointestinal tract would be responsible by inhibition of COX-1. (Rao P, Knaus EE 2008)
However different compounds cause different levels of gastric damage and analgesia and the role of the individual COX isoforms in the anti-inflammatory, analgesic and gastric damage effects of NSAIDS is not certain. (Kakuta H, Zheng X, Oda H, et al 2008). To get the best effects of ibuprofen and other NSAIDS without getting gastrointestinal bleeding and ulceration, selective COX-2 inhibitors were developed; these cause inhibition of COX 2 isoform but without inhibiting COX-1. (eMedicine 2006)
Figure 2: Mechanism of action of Ibuprofen. (Miguel 2003)http://img.medscape.com/slide/migrated/editorial/cmecircle/2004/3080/images/miguel/slide013.gif
Absorption of Ibuprofen.
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The absorption of ibuprofen is rapid and complete when given orally. It is known that approximately 80% of the oral dosage is absorbed via the GI tract. The high oral absorption is due to the un-ionised form, this allows the passive diffusion from the gastrointestinal tract to be metabolise in the liver. The rate of absorption is decreased and the plasma concentrations reduced if ibuprofen tablets, suspension or chewable tablets are taken with food, but the overall extent of absorption is not affected. If administered with food the result is a reduction of peak plasma ibuprofen concentrations by 30-50% and the time to achieve peak plasma concentrations is delayed by 30-60 minutes. The rate of ibuprofen is known to be slowed by food intake, although the total area of absorption is not affected. Ibuprofen is rapidly absorbed from solutions according to first order kinetics (Knaus 2008).
Below are the observed differences in the table occurring between adults and children, in terms of AUC and Cmax. They are due to both differences in dose per body weight and age- or fever-related change in volume of distribution (Vd/F).
Pharmacokinetic Parameters of Ibuprofen Oral Suspension[Mean values (% coefficient of variation)]
Legend:AUCinf = Area-under-the-curve to infinity
Cmax = Peak plasma concentration
Tmax = Time-to-peak plasma concentration
Cl/F = Clearance divided by fraction at drug absorbed
200 mg (ââ€°Ë† 2.8 mg/kg) in
10 mg/kg in
Number of Patients
Fig 3- Pharmacokinetic Parameters of Ibuprofen Oral Suspension ( Harrison 2002)Cl/F (mL/h/kg)
A bioavailability study in adults has shown that there was interference with the absorption of ibuprofen when given in conjunction with an antacid containing both aluminium hydroxide and magnesium hydroxide (Miguel 2003).
In adults the oral bioavailability of ibuprofen is similar following administration of conventional tablets in all the above forms. Following each administrative dosage form the time it took to reach peak plasma concentrations was reportedly about 120, 62, or 47 minutes. After taking a single 200-mg dose of ibuprofen in its chewable, suspension or conventional tablets the peak plasma were recorded at 15, 19 or 20 mcg/mL. In children, the oral bioavailability seems to be similar to that of the adults. Where it differs is the time it is taken to reach peak plasma concentrations which was taken 86 or 58 minutes respectively, in a suspension or chewable form (Avram 1969).
The effect on adults of oral administration of 200mg dose the peak plasma concentrations and plasma concentration-time curves (AUCs) of ibuprofen show an increased output compared to that of adults. (Zheng 2008)
The area under the plasma concentration-time curve (AUC) of ibuprofen is dose-dependent. Ibuprofen binds extensively, to plasma albumin occurring in a concentration form. If the dosage is greater than 600mg there is an increase in the unbound fraction of the drug, leading to an increased clearance of ibuprofen and a reduced AUC of the total drug. High concentrations of ibuprofen are obtained in synovial fluid, which is a proposed site of action for nonsteroidal anti-inflammatory drugs. (Zheng 2008)
Elimination of Ibuprofen.
Drug elimination refers to the irreversible loss of drug from the body (H.P. Rang, 2007, 113). The major way, in which Ibuprofen is eliminated from the body is through urine. The urine can contain approximately 80% of Ibuprofen related material. As Ibuprofen starts to get eliminated and metabolised, it results in the plasma volume containing the total amount of drug, falling to half. The elimination half life of Ibuprofen is 2 hours. Ibuprofen has a fast metabolism rate through the primary route of oxidation metabolism and excretes inactive metabolites through urine, within 24 hours. Studies show that less than 10% of unchanged Ibuprofen is excreted in urine. (H.P. Rang, 2007, 113).
Another method for elimination of Ibuprofen is in breast milk, where approximately 1 mg of a racemic dose of 400 mg is eliminated per day, due to its high acidic nature (K.D. Rainsford, 118). Biliary elimination is another way to eliminate Ibuprofen, this is a minor pathway for elimination. After administrating a dose of 600 mg a minimum of 2% can be recovered in bile (K.D. Rainsford, 118).
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Ibuprofen is a chiral nonsteroidal anti-inflammatory drug (NSAID) of the 2 arylpropionic acid (2-APA) class. It has been identified that the absorption of ibuprofen is rapid and complete when given orally. The major route of excretion is known to be via the kidney, with a high 95% of ibuprofen being excreted in the urine within 24 hours of a single dose. It is absorbed steadily after oral administration with peak plasma levels 30-60 minutes and has an absolute absorption rate of 80% via the GI tract. This bioavailability is quite high when compared to other medicines and this means that 80% of the drug is available to the body after first pass. It comes in various forms including tablets coated and non coated tablets or liquid and is taken orally.