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PubMedDate not supplied

A re-evaluation of the HSA-piroxicam interaction.

Piroxicam binding to HSA was studied using equilibrium dialysis and fluorescence methods. It was shown that this drug, like its analogs isoxicam and tenoxicam, binds to the apazone locus (site I area) and to a lesser extent to the diazepam site (site II). The piroxicam binding to HSA can be modulated by various specific ligands--apazone, warfarin, diazepam, ibuprofen--and these drug interactions have to be considered not only as potential displacement from the HSA binding sites but also in terms of induced allosteric effects.

Apazone↗
PubMed1989

Blood distribution of tenoxicam in humans: a particular HSA drug interaction.

Blood binding of tenoxicam was studied in vitro by equilibrium dialysis. Isolated human plasma proteins and blood cells were checked, and the distribution of the bound form was then calculated. The results showed that tenoxicam is mainly bound to HSA and that binding percentages are not different when measured in plasma (98.4%) and in an HSA solution at physiological concentration (704 microM, 98.15%). In these conditions, within the range of 1-150 microM, the tenoxicam binding percentage remained constant, evidence of a nonsaturable process. When a lower HSA concentration (10 microM) was used, the binding parameters of the tenoxicam interaction were calculated by using the same equilibrium dialysis data, by 3 methods of analysis- a stoichiometric method and site-oriented methods, fixing or not the number of HSA binding sites (n) as integer values. The best fit was observed with the first method, suggesting that two main interactions occurred. The site-oriented method gave lesser fits, the better being observed when n was not fixed. Its value, 1.77, suggest the possibility of two binding sites, one of them not preformed. The effects of known markers of site I, warfarin and apazone, of site II, diazepam and ibuprofen and of palmitic acid showed that tenoxicam is bound simultaneously to both sites I and II. The binding capacity of site I for tenoxicam is enhanced by diazepam: as this compound alone is bound to site II, this result suggests that the two HSA binding sites are not independent.

Bilirubin↗
PubMed1991

The problems and pitfalls of NSAID therapy in the elderly (Part I).

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most commonly prescribed drugs worldwide when grouped by generic categories and account for 3 to 9% of total prescription numbers in various countries. While NSAIDs are responsible for approximately 25% of all reported adverse drug reactions, aging may substantially increase the risk of NSAID-induced reactions. Several factors may contribute to NSAID-related toxicity in the elderly. The increase in morbidity associated with aging may result in consumption of a wide range of potent drugs, while inappropriate drug therapy and aberrant compliance are also capable of contributing to adverse drug reactions in geriatric patients. Age-related alterations in pharmacokinetics may influence the handling of NSAIDs in the elderly; in particular, dosage reduction is appropriate for azapropazone (apazone), naproxen, ketoprofen and salicylates administered to healthy aged patients, whereas the presence of renal disease may also necessitate dosage reduction of diflunisal, indomethacin, sulindac and mefenamic acid. Changes in NSAID pharmacodynamics with aging, such as increased CNS sensitivity to NSAIDs and impaired homeostasis, also predispose the elderly to NSAID-related adverse effects. It is undisputed that gastrointestinal toxicity due to NSAID therapy is a class effect. A significant association has been found between aspirin and uncomplicated gastric, but not uncomplicated duodenal ulcer, while nonaspirin NSAIDs are significantly associated with both uncomplicated gastric and duodenal ulceration. The use of NSAIDs is accompanied by a 2- to 5-fold risk of serious complications of peptic ulcer disease, i.e. haemorrhage or perforation, which increases in the elderly, particularly women. A broad range of renal side effects has been ascribed to NSAIDs, of which acute renal impairment is the most common in the elderly. Although most NSAIDs have been reported to cause hepatotoxicity, serious abnormalities of liver function are rare and are largely unpredictable. Other adverse effects due to NSAIDs have also been described, some of which (e.g. cardiovascular, CNS and haematological effects) may be more common in the elderly.

Aged↗
PubMed1990

Excretion of azapropazone in human breast milk.

The excretion of azapropazone in breast milk was studied in four lactating women over one dosing interval following repeated doses of 600 mg b.d. for at least three days. Plasma and milk samples were collected up to 12 hours after drug intake. An average of 0.8 mg azapropazone was calculated as being excreted in breast milk in the 12 hour period. The breast fed neonate would ingest 0.2 mg/kg during this period.

Administration, Oral↗
PubMed1990

The amphiprotic character of azapropazone and its relevance to the gastric mucosa.

Since most non-steroidal anti-inflammatory drugs (NSAIDs) contain only one obvious ionisable group at physiological pH levels then they may be easily identified as having either acidic or basic character. Basic NSAIDs are simply non-acidic NSAIDs capable of accepting a proton within the physiological pH range. Within this range, however, a few NSAIDs contain two obvious ionisable groups, one acidic and the other basic. Such compounds should be described as amphiprotic, and include NSAIDs such as 4- and 5-amino substituted salicylic acids, niflumic acid, amfenac, WY 18251, and azapropazone. The aqueous ionisation equilibrium of such compounds is complex and is described by two macroscopic ionisation constants. Evidence has accumulated during the last decade to support the view that the pharmacokinetic behaviour of NSAIDs contributes not only decisively to their therapeutic effects but also to the type and incidence of their side-effects. A priori, using a physicochemical argument, certain amphiprotic NSAIDs should be better tolerated by the gastric mucosa than the classical acidic compound. Of those NSAIDs commercially available in the United Kingdom azapropazone remains the only one for which amphiprotic behaviour has been described. Following our examination of available data for azapropazone we conclude that the use of amphiprotic compounds represents a logical approach towards solving the problem of NSAID-induced gastric mucosal damage.

Animals↗
PubMed1978

Interaction between azapropazone and warfarin.

In vitro studies, using 2 separate techniques, have shown that the anti-inflammatory agent azapropazone caused displacement of warfarin from its plasma albumin binding and it is therfore suggested that such a displacement mechanism may be involved in the reported clinical interaction between these 2 drugs.

Apazone↗
PubMed1987

The interpretation of ligand displacement experiments: calculations for multisite acceptors.

A method is described for calculating the degree of competition for binding between two ligands which are bound at any number of site classes on a binding protein from a generalization of the equilibrium competitive binding equations, the protein's binding parameters for each of the ligands, and the total protein and ligand concentrations. Theoretical displacement curves thus obtained for each of the possible competitive binding models with a multisite protein can then be compared with experimentally determined ligand displacements in order to find which model is most realistic or if measured displacements are due rather to negative cooperativity effects. The binding parameters used for the calculations have a statistical error attached to them, since they have been obtained experimentally, so here we also propose a method for calculating the standard deviations of the theoretical displacement curves deriving from these errors. This permits the use of statistical hypothesis testing in the comparison of theoretical and experimental results. An example is shown in which this method permits the verification that two drugs (phenylbutazone and azapropazone) are both bound by the same high- and low-affinity sites of a protein (alpha-fetoprotein).

Apazone↗
PubMed1989

Effect of non-steroidal anti-inflammatory drugs on the course of osteoarthritis.

To test the hypothesis that non-steroidal anti-inflammatory drugs (NSAIDs) accelerate the progression of osteoarthritis by reducing synthesis of vasodilator prostaglandins, thereby diminishing joint perfusion, 105 osteoarthritis patients awaiting hip arthroplasty were treated prospectively with a strong or weak prostaglandin synthesis inhibitor, indomethacin or azapropazone, respectively. Pain and radiological joint space were monitored during the period up to arthroplasty and the condition of the excised femoral head was determined. As judged by radiological and histopathological data, the two treatment groups were at a similar pathophysiological end-point when they came to arthroplasty. In the indomethacin group the affected hips lost joint space more rapidly than did the contralateral hips, a difference not seen in the azapropazone group. The patients receiving azapropazone, who had higher concentrations of synovial vasodilator prostaglandins, took longer than the indomethacin group to reach the arthroplasty end-point. Potent inhibitors of prostaglandin synthesis may be inappropriate in the management of osteoarthritis of the hip.

Aged↗
PubMed1978

Azapropazone and renal function.

Renal concentrating ability was measured in two groups of arthritic patients. The first had received long-term therapy with azapropazone and the second with other nonsteroidal anti-inflammatory drugs. Even after long periods of treatment, azapropazone did not adversely affect renal concentrating ability.

Adult↗
PubMed1989

Myocardial cytoprotective efficacy of azapropazone in a canine heart model of regional ischemia and reperfusion.

The present study assessed the efficacy of azapropazone (AZA) in pentobarbital-anesthetized dogs subjected to 120 min of regional ischemia [left anterior descending coronary artery (LAD) ligation] followed by 5 h of reperfusion. Azapropazone was given 30 min prior to LAD occlusion (100 mg/kg i.v.), 35 min prior to LAD release (50 mg/kg, i.v.), and at 2.5 h postreperfusion (50 mg/kg i.v.). Regional myocardial blood flow (RMBF) and area at risk (AAR) were determined with radiolabeled microspheres. The degree and extent of ischemia (anaerobic metabolism) and necrosis were delineated with 14C-deoxy-2-D-glucose (14C-DG) and 111In-antimyosin, respectively, in control (n = 7) and AZA (n = 7)-treated groups. In mild (60-80% normal RMBF) and moderate (30-60% normal RMBF) flow-restricted areas, AZA resulted in a significant decrease in the degree and extent of ischemia (p less than 0.01) with the limitation of infarct size (p less than 0.01). However, AZA did not produce a significant infarct size limitation in the severe flow-restricted area (0-30% of normal RMBF). The effect of AZA is expressed primarily in moderate flow-restricted myocardium with the subsequent infarct size limitation.

Anaerobiosis↗
PubMed1991

Persistent cardioprotection by azapropazone in a canine model of coronary artery thrombosis and thrombolysis.

Activated neutrophils and possibly xanthine oxidase-derived free radicals are believed to be mediators of ischemia and reperfusion-induced myocardial damage. We studied the cardioprotective effect of the neutrophil stabilizer and xanthine oxidase inhibitor azapropazone in dogs subjected to thrombotic occlusion of the left anterior descending coronary artery (LAD), induced by intracoronary introduction of a copper coil, followed 60 min later by thrombolytic treatment with intracoronary streptokinase and 4-day reperfusion; we then determined infarct size by triphenyltetrazolium stain. Azapropazone [100 mg/kg intravenously (i.v.) followed by a 24-h i.v. infusion of 10 mg/kg/h, n = 8] or vehicle (n = 10) treatments were started immediately before the streptokinase infusion. Steady-state plasma levels of azapropazone ranged from 97 to 163 micrograms/ml during the infusion. Myocardial blood flow and underperfused area at risk were determined using radiolabeled microspheres. Results were as follows (mean +/- SEM): area at risk (percentage of left ventricle) azapropazone 22.7 +/- 3.16 and vehicle 21.8 +/- 4.13; infarct size (percentage of area at risk), azapropazone 45.1 +/- 11.8 and vehicle 75.7 +/- 10.6, p less than 0.03; collateral blood flow (ml/min/g), azapropazone 0.27 +/- 0.02 and vehicle 0.23 +/- 0.02; total ischemic period (min), azapropazone 106 +/- 5.9 and vehicle 91.5 +/- 4.9. Azapropazone had no effects on heart rate (HR), blood pressure (BP), or rate/pressure product (RPP). These dta show that azapropazone limits infarct size in a canine model of coronary thrombosis and long-term reperfusion and that this cardioprotection is independent of cardiovascular parameters.

Animals↗
PubMed1991

Protection from gastrointestinal side-effects by azapropazone by its incorporation into a glucose-sodium acid citrate formulation.

Addition of glucose and sodium citrate to azapropazone, in proportions of 1:1:1 by weight reduced gastric mucosal damage in rats and there was a trend towards reduction in radiolabelled faecal red cell loss in human volunteers compared with that with azapropazone alone. The glucose and citrate did not affect the pharmacokinetics of azapropazone, or its therapeutic efficacy. While no difference was observed in endoscopic injury and in symptomatic gastrointestinal complaints in a multicentre comparison in rheumatic patients, a striking reduction in symptoms was observed in those patients with a history of severe gastrointestinal intolerance to non-steroidal anti-inflammatory drugs.

Adolescent↗
PubMed1991

A comparison of azapropazone and aspirin for pain relief following dental extractions.

Eighty patients received one of three treatments after elective dental surgery involving multiple extractions. Group A received aspirin 600 mg, group B azapropazone 300 mg and group C azapropazone 600 mg. All drugs were administered in a double-blind fashion. Quality of analgesia was unsatisfactory for all treatments; over 30% of patients required supplementary analgesia with an opioid. In addition there were a large number of withdrawals from the study. There were no significant differences in analgesic efficacy between groups.

Adolescent↗