Screening major binding sites on human serum albumin by affinity capillary electrophoresis.

A screening method is described for determining whether a drug or small solute has significant interactions at the two major binding sites on human serum albumin (HSA). This method uses affinity capillary electrophoresis (ACE) to perform a mobility shift assay, where the solute of interest is injected in both the presence of pH 7.4, 0.067 M phosphate buffer, and the same buffer containing a known concentration of HSA. Dextran is also used in the running buffer to adjust the mobility of HSA. Two types of modified HSA are used in this assay. The first is modified with 2-hydroxy-5-nitrobenzyl bromide (HNB), which selectively blocks HSA's warfarin-azapropazone site. The second type of HSA is modified with tetranitromethane (TNM), which decreases binding at the indole-benzodiazepine site. By comparing the mobility of a solute in the presence of these two modified forms of HSA vs normal HSA, it is possible to detect solute interactions at these binding sites. This approach is illustrated using warfarin and ibuprofen as examples of test solutes.

Repeated cyclosporine therapy of peripheral arthritis associated with ankylosing spondylitis.

BACKGROUND: A case history of a patient with ankylosing spondylitis and peripheral arthritis unresponsive to the conventional drug therapy, but successfully controlled by the use of cyclosporin. MATERIAL AND METHODS: In a 68 years old female patient with a 36 years history of typical ankylosing spondylitis a peripheral polyarthritis (hands, feet, wrists, and knees) developed. The patient did not suffer any other disease known to cause secondary spondylitis (psoriasis, inflammatory, bowel, disease). After the unsuccessful use of non-steroidal antiinflammatory drugs a combination therapy with cyclosporin (4 mg/kg/day) and azapropazone (300 mg t.i.d.) was introduced. RESULTS: Clinical improvement was achieved after 6 months of combined therapy, the polyarthritis completely resolved after one year. Therefore cyclosporin was discontinued. After one year the polyarthritis reappeared therefore the cyclosporin therapy was reinstituted with success. CONCLUSION: Cyclosporin has proved consistently effective in our case to control the peripheral arthritis associated with ankylosing spondylitis.

Pharmacotherapy for Behcet's syndrome.

OBJECTIVES: To determine the effects of available pharmacological interventions in treating the different clinical features of Behcet's syndrome. SEARCH STRATEGY: We searched the Cochrane Musculoskeletal Group's trials register, the Cochrane Controlled Trials Register, and Medline up to January 1998. The computer search was complemented by a hand search of all bibliographic references from the reference lists of included trials. Principal investigators were contacted to seek unpublished literature. All languages were included. SELECTION CRITERIA: Studies were eligible if they fulfilled all of the four following criteria: 1. Randomized controlled trials, single or double-blind; 2. Participants were patients with Behcet's Syndrome as defined by the International Study Group, 1990 (Int Study Group, 1990); 3. Interventions included any pharmacological therapy compared to placebo or some other pharmacological intervention for the treatment of Behcet's syndrome. 4. Outcome measures included active ocular inflammatory processes, arthritis, mucocutaneous manifestations (oral ulcer, genital ulcer, erythema nodosum), laboratory changes and major events such as adverse effects and death. DATA COLLECTION AND ANALYSIS: The 32 potentially relevant references were assessed by two independent reviewers (MA, AS) according to the inclusion criteria. Ten trials fit the inclusion criteria and were included in this review. From the 10 included trials, data were independently extracted by the same two observers and crosschecked. The quality of the included trials was assessed independently by two observers (MA, AS) using a validated scale (Jadad 1996). For dichotomous measures, the treatment effect for each trial was calculated using a fixed effect model [Peto model (Petitti 1994)]. The weighted mean differences were based, if available, on end-of-trial results. The analysis was conducted separately for each different intervention. Since the trials could not be pooled it was not possible to carry out a sensitivity analysis by quality scores or a subgroup analysis by drug dosages. Because of this lack of comparability across trials and the small number of trials, we could not conduct a heterogeneity test or a funnel plot. MAIN RESULTS: Ten trials and 679 patients were included. The main results were the lack of efficacy of some of the classic treatments for Behcet's syndrome, including colchicine, cyclophosphamide and steroids for eye involvement, azapropazone and colchicine for arthritis and acyclovir, colchicine and topical interpheron for aphthas. The results confirm the protective effects of cyclosporine and azathioprine for eye involvement and benzathine-penicillin for arthritis. REVIEWER'S CONCLUSIONS: We conclude that further randomized, placebo-controlled, double-blind trials should be carried out to compare cyclosporine, azathioprine and benzathine-penicillin versus placebo in order to make the results generalizable and comparable.

Development of tryptophan-modified human serum albumin columns for site-specific studies of drug-protein interactions by high-performance affinity chromatography.

Human serum albumin (HSA) is one of the main proteins involved in the binding of drugs and small solutes in blood or serum. This study examined the changes in chromatographic properties that occur for immobilized HSA following the chemical modification of HSA's lone tryptophan residue (Trp-214). Trp-214 was reacted with o-nitrophenylsulfenyl chloride, followed by immobilization of the modified protein and normal HSA onto separate silica-based HPLC supports. The binding properties of the modified and normal HSA were then analyzed and compared by using frontal analysis and zonal elution experiments employing R/S-warfarin and L-tryptophan as probe compounds for the warfarin and indole binding regions of HSA. The modified HSA was found to have the same number of binding sites as normal HSA for R-warfarin and L-tryptophan but lower association equilibrium constants for these test solutes. Zonal elution studies with R- and S-warfarin on the modified HSA column demonstrated the importance of Trp-214 in determining the stereoselective binding of HSA for these agents. These studies also indicated that tryptophan modification can alter HSA-based separations for chiral solutes.

Drug binding sites on chicken albumin: a comparison to human albumin.

Mammalian albumins have two main structurally selective ligand binding sites. Site I binds drugs such as azapropazone, phenylbutazone and warfarin; whereas benzodiazepines, some dansyl amino acids, such as dansylsarcosine, and short chain fatty acids like octanoic acid interact with site II. However, it is not known if non-mammalian albumins have similar binding loci. In this study, drug binding sites on chicken albumin were investigated using site selective fluorescent probes (warfarin and dansylsarcosine) and p-nitrophenyl acetate (NPA); the hydrolysis of which is selectively inhibited by site II ligands. Azapropazone and phenylbutazone decreased the binding of warfarin and dansylsarcosine to a similar extent. Diazepam and octanoic acid also inhibited binding of the two fluorescent probes in a non-selective manner. However, the fluorescence intensity of the warfarin-chicken albumin complex decreased when the pH was increased from 6.0-9.0; but by contrast, the fluorescence of bound dansylsarcosine remained unchanged. Furthermore, the hydrolysis of NPA was selectively inhibited by dansylsarcosine, diazepam and octanoic acid (ligands selective for site II on mammalian albumins), but not by site I selective ligands such as azapropazone and warfarin. Overall, the results suggest that chicken albumin, like mammalian albumins, has discrete binding sites for warfarin and dansylsarcosine.

Effects of azapropazone on pain-related brain activity in human subjects.

1. The dose-related effects of azapropazone on (i) event-related and spontaneous EEG-activity and (ii) the subjects' pain ratings were investigated using an experimental human pain model based on both chemo-somatosensory event-related potentials (CSSERP) and subjects' pain ratings. 2. Healthy subjects (n = 20) participated in a placebo-controlled, randomized, double-blind, four-way cross-over study. Single doses of azapropazone (300 mg, 600 mg and 1200 mg) and placebo were administered intravenously. Each experiment consisted of five sessions (before and 1, 2, 4 and 8 h after administration of the medication). Each session lasted for approximately 40 min. In the first 20 min, pain was induced by short CO2-stimuli presented to the right nostril (phasic pain; interstimulus interval 30 s) and EEG was recorded from five positions. CSSERPs were obtained in response to painful CO2-stimuli. In the following 20 min period, tonic pain was induced by a constant stream of dry air introduced in the left nostril. Subjects rated the intensity of both phasic and tonic pain by means of a visual analogue scale. Additionally, a frequency analysis of the spontaneous EEG was performed. 3. Azapropazone reduced the pain-related CSSERP-amplitudes at frontal and parietal recording positions. This topographical pattern was observed in previous studies with opioids, while NSAIDs such as flurbiprofen and ketoprofen exerted effects at frontal and central positions. In contrast to other NSAIDs, administration of azapropazone resulted in a reduction of the frequency bands alpha 1, delta and theta of the spontaneous EEG. At the subjective level, analgesic effects of azapropazone were observed in the ratings of tonic pain. 4. Analgesic properties of azapropazone were demonstrated in man. The topographical pattern of the changes in the CSSERPs and the effects on EEG background activity suggest a central component of the analgesic action of azapropazone.

Inefficacy of azapropazone in the acute arthritis of Behçet's syndrome: a randomized, double blind, placebo controlled study.

Sixty-three consecutive Behçet's syndrome patients with an acute arthritis of up to 10 days duration were treated either with azapropazone (APZ) 300 mg t.i.d. or placebo for three weeks. Twenty-eight patients (14 males, 14 females: mean age 36.2 +/- 8.1 SD years) from the APZ group and 29 patients (18 males, 11 females; mean age 34.2 +/- 8.4 SD years) from the placebo group completed the trial. At the end of the trial the arthritis persisted in 53.5% (15/28) of the APZ patients and in 41.3% (12/29) of the placebo patients (chi 2 = 0.85; NS). Six patients (6/28; 21%) from the APZ group and 9 patients (9/29; 31%) from the placebo group developed new joint involvement (chi 2 = 0.7; NS). There was no difference in the duration of arthritis between the two groups (19.9 +/- 8.3 SD days in the APZ groups vs. 19.7 +/- 8.2 SD days in the placebo group; NS). The degree of joint swelling, the tender joint score and the visual analogue score for pain significantly improved in both groups, but there was no difference in any of these parameters between the groups except for a significant difference in the visual analogue score for less pain at the first week in the azapropazone group (t = 2.23; p < 0.05). There were also no differences in the mean numbers of acetaminophen tablets used or in the CRP and ESR levels between the two groups. We conclude that azapropazone is not effective in controlling the arthritis of Behçet's syndrome.

Lack of activity of azapropazone in the hot-plate test and in 5-HT1A and 5-HT2 receptor subtypes in rat brain membranes.

This study aimed to investigate the antinociceptive activity of azapropazone (AZA), a weak prostaglandin synthesis inhibitor using the hot-plate test, and its ability to modify the serotonin-binding capacity in rat brain membranes. It revealed that AZA had no antinociceptive effect in the hot-plate test at the doses of 400 and 600 mg/kg when orally administered (p.o.), and at 400, 500 and 600 mg/kg after intraperitoneal injection (i.p.). At the dose of 600 mg/kg i.p. the drug failed to modify the number and the affinity of 5-HT1A and 5-HT2 receptors in rat brain membranes. In accordance with our previous findings on a positive correlation between NSAIDs antinociception in this experimental model and changes in 5-HT receptor characteristics, these results suggest an association between the lack of AZA-mediated antinociception in the hot-plate test and the drug's inability to modify the characteristics of 5-HT1A and 5-HT2 receptor binding sites in rat brain membranes.

Effects on platelet functions and pharmacokinetics of azapropazone and ketorolac tromethamine given as single parenteral doses.

The biosynthesis of thromboxane (TX) B2 and immunoreactive prostaglandin (PG) F2 alpha in clotting whole blood ex vivo as well as collagen-induced platelet aggregation were determined before and up to 72 h after intravenous injection of 600 mg azapropazone 2H2O and intramuscular injection of 30 mg ketorolac tromethamine in six healthy subjects. The drug doses were selected on the basis of comparable analgesic activity (maximal recommended analgesic dose). Both platelet aggregation and prostanoid biosynthesis were inhibited by racketorolac to a significantly greater extent and for a longer period of time than by azapropazone. Correlations between serum concentrations and the inhibitory effects on TXB2 biosynthesis were observed for both drugs. Using the sigmoidal Emax model the mean serum concentration of azapropazone inhibiting platelet TXB2 generation by 50% (EC50) was found to be 98.1 +/- 41.9 (s.d.) micrograms ml-1, a value 1000 times higher than that for rac-ketorolac. The moderate inhibition of platelet function by azapropazone as compared with rac-ketorolac might be an advantage with regard to its use as a post-operative analgesic.

Photoproducts of benzydamine and azapropazone: demonstration of their phototoxicity in vitro.

Red blood cell lysis, photosensitized by the products of the aerobic photolysis of benzydamine (1) and azapropazone (4), was investigated. Irradiation of a methanol solution of 1 and 4 under oxygen produces the photoproducts 3-hydroxy-benzydamine, (2), 2-(3-dimethylaminopropyl)-1-benzylindazolin-3-one (3) and 3-dimethylamino-7-methyl-1,2,4-benzotriazine (5). The mechanism of the photodegradation of 1 was examined. Photoproducts 3 and 5 produce singlet oxygen as demonstrated by trapping with 2,5-dimethylfuran. The photohemolysis rate for the photoproducts 3 and 5 was enhanced by deuterium oxide and oxygen. No change was observed in the presence of reduced glutathione. The photohemolysis rate was low under anaerobic conditions.

Effects of chronic NSAIDs on gastric mucosal injury related to mucosal prostanoids, and plasma drug concentrations in human volunteers.

The relationship between endoscopically observed gastric mucosal damage, elicited following repeated oral intake for 7 d of four NSAIDs, to their effects on antral and fundic production of PGE2, 6-keto-PGF1 alpha and TxB2 (assayed by GC-MS), mucosal histology and plasma concentration profiles was studied in 40 normal males. Subjects received azapropazone (APZ) 600 mg b.i.d., indomethacin (IND) 50 mg t.i.d., naproxen (NAP) 500 mg b.i.d., piroxicam (PIR) 20 mg qq.d., or one placebo capsule t.i.d. (N = 8/group). Plasma NSAIDs (HPLC) levelled at 7 d. Mucosal damage occurred in the antrum region with IND and NAP. APZ and PIR exhibited no differences compared to placebo. NAP and IND reduced all three prostanoids in the antrum while APZ and PIR were ineffective. Fundic PGE2 was reduced by IND, NAP and PIR; APZ had no effects. Thus, mucosal damage relates to effects on prostanoid production in the antrum but not in the fundus.

Measurement of non-steroid antiinflammatory drugs induced gastric microbleeding.

The damage of the mucous membranes in the gastrointestinal tract caused by non-steroid antiinflammatory drugs are well known. The gastrointestinal microbleeding was measured by the method of Fischer and Hunt before and after the intake of indomethacin (4 x 25 mg), naproxen-sodium (4 x 275 mg), diclofenac (3 x 50 mg) and azapropazone (2 x 600 mg). In the indomethacin group microbleeding increased from 0.91 +/- 0.12 ml/24 h to 7.30 +/- 1.20 ml/h. In the naproxen-sodium group from 1.22 +/- 0.16 ml/24 h to 3.56 +/- 0.40 ml/24 h, in the diclofenac group from 0.86 +/- 0.14 ml/24 h to 3.18 +/- 0.28 ml/24 h, in azapropazone group from 0.92 +/- 0.18 ml/24 h to 2.50 +/- 0.20 ml/24 h, respectively. All non-steroid antiinflammatory drugs increased the gastric microbleeding, however, there were considerable differences in the degree of enhancement. This can be explained by the different inhibitory activities of the drugs on the cyclooxygenase enzyme activity.

A new approach to encapsulating non-steroidal anti-inflammatory drugs. V. Biopharmaceutical study of microcapsules of azapropazone coated with pectin and rutin.

Azapropazone was encapsulated with pectin-rutin mixture using the fluidized bed technique. The encapsulated particles showed higher dissolution rate and bioavailability but lower ulcerogenic activity as compared with the drug alone.

Quantitative contribution of endogenous compounds and hypoalbuminemia in reducing the binding of furosemide in the plasma of newborn infants.

The protein binding of furosemide was studied in the plasma of newborn infants and adult subjects. Plasma consisted of two pools obtained from 25 newborns and adult subjects. The concentrations of albumin were 36.8 (newborn) and 48.3 g/l (adult). The unbound fraction of furosemide was 1.38 +/- 0.15 (adult) and 2.03 +/- 0.13% (newborn; p < 0.001). After extensive dialysis of the plasma, the unbound fraction of furosemide was 1.12 +/- 0.15 (adult) and 1.39 +/- 0.09% (newborn; p < 0.0001), suggesting that dialyzable endogenous compounds interfere with the binding of furosemide. The addition of human albumin to the newborn plasma to give a final albumin concentration of 48.3 g/l yielded an unbound fraction of furosemide of 1.63 +/- 0.08 (nondialyzed plasma) and 1.17 +/- 0.08% (dialyzed plasma; p < 0.0001). The addition of albumin to the dialyzed newborn plasma, to give a final albumin concentration similar to that in adult plasma, decreased the unbound furosemide to the level of the dialyzed adult plasma. The binding defect of furosemide in newborn plasma reflects either the effects of the endogenous inhibitors or of hypoalbuminemia. The intrinsic binding properties for furosemide of newborn dialyzed plasma are similar to those of dialyzed adult plasma. This consideration corroborates our previous results on the binding of furosemide and diazepam, salicylic acid and digitoxin to newborn and adult albumin. The displacement of furosemide by salicylic acid, tolbutamide and azapropazone is 70% greater in newborn than in adult plasma. The greater displacing effect is largely due to hypoalbuminemia.

A controlled trial of azapropazone in tinnitus.

A single-blind placebo-controlled trial of azapropazone, a non-steroidal anti-inflammatory drug, is presented in 10 patients with tinnitus. Seventeen variables were assessed by questionnaire and six by a daily diary. In none of these was there a significant difference between placebo and drug. A larger trial is probably therefore not justified.

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.