Prostaglandin E2 stimulates the osteoclastic reabsorption of juxtaarticular bone; its inhibition by nonsteroidal anti-inflammatory agents may, therefore, retard the process of bone erosion in rheumatoid arthritis and in other inflammatory processes.
Inhibition of prostaglandin synthesis by these drugs accounts for many of their major toxic effects, including gastritis, which is the most common side effect; precipitation or aggravation of renal failure; fluid retention; hyperkalemia; antiplatelet effects with hemorrhagic phenomena; and aggravation of asthma and rhinosinusitis. Inhibition of prostaglandin synthesis can, therefore, account for most of the therapeutic as well as toxic effects of the nonsteroidal anti-inflammatory agents.
Thromboxane A2 a substance that promotes coagulation is produced from platelet COX, and acts as a potent aggregant agent. Prostaglandins also have pathophysiologic effects such as erythema and increased local blood flow, hyperalgesia, probably due to sensitization of pain receptors, and increased body temperature at the hypothalamus through cytokine stimulation. When prostaglandin production is increased, there is increased sensitivity to pain and fever and increased inflammatory response.
Nevertheless, prostaglandins are also capable of anti-inflammatory action due to suppression of IL-1 and TNF synthesis. Mechanism of action The mechanism of action of NSAIDs consists in suppression of COX enzymes, resulting in reduction of the production of prostaglandins, thus controlling inflammation, pain and fever. COX 1 inhibition is associated with increased risk of gastrointestinal bleeding and damage.
Selective and specific COX 2 inhibitors were developed in an attempt to reduce the incidence of adverse effects of COX 1 inhibition. The NSAID dose necessary to reduce inflammation is larger than that needed to inhibit prostaglandin formation, suggesting that other mechanisms mediate the anti-inflammatory effects.
In addition to suppressing prostaglandin production, current anti-inflammatories inhibit specific proteases involved in breaking down proteoglycans and collagens in cartilage, and inhibit the generation of oxygen free radicals, particularly superoxide.
A study of 11 children with neoplasias assessed the pharmacokinetics of celecoxib. They also observed that absorption of the medication is optimized when taken with a fat-rich meal. In a study undertaken with 18 patients with juvenile rheumatoid arthritis, the pharmacokinetics of meloxicam suspension was evaluated, with greater elimination of the medication being observed in the younger children, although with a similar half-life to other age groups. Acetylsalicylic acid, naproxen, ibuprofen and tolmetin are the only ones approved for pediatric use by the Food and Drug Administration FDA.
Despite not being licensed for the pediatric age group, indomethacin is used to control fever and pain in children and adolescents with juvenile idiopathic arthritis JIA. Selective COX 2 inhibitors are indicated for patients who exhibit adverse effects that are confirmed to be related to nonselective NSAID use, such as gastric intolerance that cannot be controlled by combination with gastroprotective medication.
In the pediatric age group, the use of COX 2 is limited since a majority of these medicines are contraindicated before 18 years of age. Nonsteroidal anti-inflammatories are routinely employed by many specialties. Pediatricians, otorhinolaryngologists, rheumatologists, gynecologists and orthopedists prescribe these medicines the most often. It is important to point out that this recommendation is based on the results of few studies involving small numbers of patients, and there are reports of sporadic cases with significant worsening of asthma with the use of selective COX 2 inhibitors.
Martin-Garcia et al. Only the subset given rofecoxib did not exhibit any exacerbation of preexisting asthma. Etoricoxib, another selective COX 2 inhibitor, was also shown to be safe when used on patients with urticaria and angioedema.
Nonselective anti-inflammatories are COX inhibitors and the theoretical explanation for this mechanism may be based on the fact that these enzymes are responsible for synthesis of proinflammatory PGD2 and anti-inflammatory prostaglandins PGE2. PGE2 inhibits synthesis of leukotrienes LTB4 ; therefore blocking production of PGE2 could increase production of leukotrienes, with deterioration of clinical symptoms. Although age over 60 years, previous history of gastrointestinal complications and concurrent corticosteroid use are the principal risk factors for severe gastrointestinal complications from NSAID use, we must not forget that chronic use of these medicines can result in esophagitis, gastritis or duodenitis, gastric or duodenal ulcers, even if subclinical, in children and adolescents.
Although in general children complain less than adults, especially about gastropathy secondary to NSAID use, this does not mean that they are free from endoscopic lesions, as has been demonstrated. What are the true risks? There are no studies in the literature that prove the safety of these medications under these treatment regimes.
This does not rule out the possibility of erosive damage and even bleeding from gastro-duodenal mucosa after three or four doses. Gastrointestinal events Advanced age, previous peptic ulcer, previous bleeding and concurrent use of another NSAID or corticosteroids are risk factors for gastric complications such as mucosal ulceration, reflux esophagitis, esophageal thinning and peptic ulcers.
Nevertheless, although some studies have reported lower frequencies of gastrointestinal complications with COX 2 inhibitors than with traditional NSAIDs, recent concerns regarding cardiovascular safety have limited the use of these medications. Renal events Conditions such as congestive heart failure, cirrhosis, diabetes, hypertensive nephropathy, advanced age and volume depletion constitute risk factors that can predispose patients to renal complications.
Salt retention, acute reversible renal insufficiency and tubulointerstitial nephritis are some of the undesirable effects. While selective specific COX 2 inhibitors may cause less renal alterations, they are not free from inducing some of these alterations. One study with adults who exhibited "pseudoallergic" reactions to NSAIDs showed that nimesulide and meloxicam were well-tolerated.
Central nervous system events: headaches, tingling sensations and dizziness, although possible, are rarely reported by children and adolescents. The most probable hypothesis involves an imbalance between prostacyclin and thromboxane A2. Prostacyclin is a vasodilator and inhibits platelet aggregation and vascular proliferation, while thromboxane A2 causes platelet aggregation, vasoconstriction and proliferation of smooth muscle.
Platelets, which only express COX 1, are the primary products of thromboxane A2, and endothelial cells produce prostacyclin in response to COX 2. In contrast, selective COX 2 inhibitors predominantly suppress prostacyclin, upsetting the balance in favor of thromboxane.
In a recent study with 33, patients who presented myocardial infarction, it was observed that any NSAID used at habitual doses can increase the risk of this complication, especially in older patients.
Nonsteroidal anti-inflammatory drugs are contraindicated for children and adolescents in the following situations: dyspeptic syndromes, viral diseases, compromised renal function, cardiac disease, especially congestive heart failure , liver failure, systemic arterial hypertension, coagulation disorders, history of allergic reaction to NSAIDs and the use of oral anticoagulants and hypoglycemic.
Drug interactions Nonsteroidal anti-inflammatories bind strongly to plasma proteins and as a result they may displace other medications from their binding sites, which can occurs with methotrexate, phenytoin and sulfonylureas, increasing their activity and toxicity. They are synthesized in the cell from the fatty acid arachidonic acid. The cyclooxygenase pathway produces thromboxane , prostacyclin and prostaglandin D, E and F.
Alternatively, the lipoxygenase enzyme pathway is active in leukocytes and in macrophages and synthesizes leukotrienes. Release of prostaglandins from the cell[ edit ] Prostaglandins were originally believed to leave the cells via passive diffusion because of their high lipophilicity.
The discovery of the prostaglandin transporter PGT, SLCO2A1 , which mediates the cellular uptake of prostaglandin, demonstrated that diffusion alone cannot explain the penetration of prostaglandin through the cellular membrane. The release of prostaglandin has now also been shown to be mediated by a specific transporter, namely the multidrug resistance protein 4 MRP4, ABCC4 , a member of the ATP-binding cassette transporter superfamily.The most probable hypothesis involves an essential between prostacyclin and thromboxane A2. It is particularly also expressed in the central nervous system and politics a role in fact mediation of pain and fever. Semin Intolerance Rheum.
They are synthesized in the cell from the fatty acid arachidonic acid. Nat Rev Drug Discov. Arachidonic acid also leads to production of leukotrienes, via lipoxygenase enzyme Figure 1. Prostaglandins are also involved in regulating the contraction and relaxation of the muscles in the gut and the airways.
Nevertheless, although some studies have reported lower frequencies of gastrointestinal complications with COX 2 inhibitors than with traditional NSAIDs, recent concerns regarding cardiovascular safety have limited the use of these medications. Update on nonsteroidal anti-inflammatory drugs. Safety of etoricoxib, a new cyclooxygenase 2 inhibitor, in patients with nonsteroidal anti-inflammatory drug-induced urticaria and angioedema.
NSAID use and the risk of hospitalization for first myocardial infarction in the general population: a nationwide case-control study from Finland.
COX is the first enzyme involved in producing prostaglandins from arachidonic acid. The most probable hypothesis involves an imbalance between prostacyclin and thromboxane A2. In a recent study with 33, patients who presented myocardial infarction, it was observed that any NSAID used at habitual doses can increase the risk of this complication, especially in older patients.
They are produced by almost all nucleated cells. Risks and benefits of nonsteroidal anti-inflammatory drugs in children: a comparison with paracetamol.
Selective COX 2 inhibitors can be prescribed in some cases of allergy to aspirin, but they must be used with care. When a blood vessel is injured, a prostaglandin called thromboxane stimulates the formation of a blood clot to try to heal the damage; it also causes the muscle in the blood vessel wall to contract causing the blood vessel to narrow to try to prevent blood loss. Prostaglandins Prostaglandins The prostaglandins are a group of lipids made at sites of tissue damage or infection that are involved in dealing with injury and illness. Functions[ edit ] There are currently ten known prostaglandin receptors on various cell types. New insights into the mode of action of anti-inflammatory drugs. Cyclooxygenase-2 selective inhibitors: translating pharmacology into clinical utility.
Prostacyclin is a vasodilator and inhibits platelet aggregation and vascular proliferation, while thromboxane A2 causes platelet aggregation, vasoconstriction and proliferation of smooth muscle. To date none of the COX 2 inhibitors has been liberated for use in the pediatric age group. NSAID use and the risk of hospitalization for first myocardial infarction in the general population: a nationwide case-control study from Finland. Thromboxane A2 a substance that promotes coagulation is produced from platelet COX, and acts as a potent aggregant agent.