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Twenty patients with classical or definite rheumatoid arthritis received one intra-articular injection of 40, 80, 120, 160 or 200 mg rimexolone (Org 6216) into one knee joint. Rimexolone was well tolerated and the incidence of side-effects was low. A beneficial effect was sustained over the study period of 94 days and a long-lasting effect was observed in 84% of the patients after one year and in 79% after 2 years. Safety parameters remained unaffected. Individual changes in adrenal response to ACTH and morning cortisol levels did not correlate with the dose or with serum levels of rimexolone. Rimexolone showed linear kinetics. The mean residence time in the intra-articular depot was 44 days (SD +/- 53) with a median of 26 days. Ninety percent was absorbed after 4 months. Outside the intra-articular depot the mean residence time was less than 0.1 days.

The pharmacokinetics of rimexolone were investigated after intra-articular injection into the knee joints of patients with rheumatoid arthritis. After a single dose of 40 mg rimexolone the drug could be detected in plasma over 3 months. The suspension dissolves in the synovia very slowly and provides a sustained release of the steroid in the joint. Pharmacokinetic analysis was performed on the assumption that the disposition of rimexolone after intra-articular administration is absorption limited ("flip-flop-case"). Dose linearity was studied in a range from 40 to 200 mg. Total body clearance averaged 106 L/h and was independent of dose. The mean residence time of rimexolone in the knee joint is very long and averaged 25 days. It could be shown that the mean residence time of different glucocorticoids correlates well with the duration of their clinical effectiveness.

Although current immunoassay kits for digoxin supposedly have antibodies of high specificity, serum digoxin levels in patients taking spironolactone suggest that spironolactone interferes with the determination. In vitro determinations of digoxin performed on blank serum spiked with spironolactone and its metabolite canrenone showed that contrary to the belief gained from reading the manuals of some diagnostic immunoassay kits, spironolactone significantly influences digoxin determinations.

Investigating the interference of danazol in testosterone radioimmunoassays, we measured serum testosterone concentrations in the serum of women receiving danazol, with three testosterone radioimmunoassay kits. All of these showed positive interference by danazol or its metabolites (or both). Values for testosterone obtained with two of the methods (Diagnostic Products Corp. and Farmos Diagnostica) depended on the volume of serum extracted per assay tube. A detailed column-chromatographic method is presented in which testosterone is resolved from danazol and its metabolites.

A high performance liquid chromatographic method with ultraviolet detection was developed for the determination of nivacortol (WIN 27914) in biological samples. The drug was isolated from human plasma by using a solid-phase extraction and eluted with ethanol. The solvent was evaporated and the residue dissolved in the chromatographic eluent. The sample was subjected to chromatography on a C8 silica column and eluted with a gradient of acetonitrile in 0.1 M sodium acetate buffer, pH 6.5. A single concentration of a structural analogue (WIN 31338) was used as internal standard for the quantitative determination of the analyte. The plasma concentrations were below that needed to suppress ACTH secretion by pituitary cells in culture and did not suppress plasma ACTH in Nelson's syndrome.

One-hundred and thirty-seven patients with classical or definite rheumatoid arthritis, involving at least one knee joint, were randomly allocated to a single intra-articular injection of 10, 20 or 40 mg of rimexolone (Org 6216) or placebo. The follow-up period was 84 days, during which clinical and laboratory assessments were done. Clinical improvement of the treated knee joint was measured by the following variables: pain, tenderness, morning stiffness, swelling, range of movement and walking ability. Placebo response was considerable. However, clinical improvement with rimexolone at 20 mg and 40 mg was significantly superior to placebo for most of the variables, whilst with the 10 mg dose only reduction of tenderness was significantly superior. The duration of improvement was longest with 40 mg of rimexolone. One single, intra-articular injection of this dose into the affected knee joint provided significant reduction in pain, tenderness and stiffness and improved the range of movement and walking ability for a period of 8 to 12 weeks.

The elimination half-life (T1/2) of canrenone, the principal unconjugated metabolite of spironolactone, was 59 h (range 32-105 h) in 5 patients with chronic liver disease and 37 h (range 19-48 h ) in 7 patients withcongestive heart failure. In comparison the T1/2 in normal subjects was 13.5-24 h in previous reports and 20.5 h in the present study, However there was no evidence of greater cumulation of canrenone in the plasma of those patients with a prolonged T1/2.

The plasma aldosterone radioimmunoassay developed by Ito et al. was found to be non-specific for aldosterone following administration of the spirolactones, spironolactone and canrenoate-K, in rabbits, dogs and humans. The assay interfering principle was identified as a hydroxylated derivative (M-B) of canrenone, which itself is a metabolite common to both spironolactone and canrenoate-K. The metabolite M-B possessed a high cross-reactivity to the 21-hemisuccinate aldosterone antibody relative to other spirolactones. A modified procedure was developed specific for plasma aldosterone in the presence of M-B. Following single doses of spironolactone and canrenoate-K, aldosterone plasma levels were unchanged in humans and in dogs and decreased in rabbits.

A sensitive method is described for the radioimmunoassay of danazol in monkey and human plasma. Antiserum was developed in rabbits, and a second antibody was used to separate bound from free danazol. The radioimmunoassay was specific for danazol, and the limit of detection ranged from 1.4 to 2.8 ng/ml. Exogeneous danazol could be quantitated accurately in both monkey and human plasma. The radioimmunoassay results agreed with values obtained by inverse isotope dilution after intravenous administration of 14C-danazol to monkeys. The assay was used successfully to measure danazol in plasma from human volunteers receiving 200 mg of danazol.

Plasma levels of canrenone and 'total metabolites' after base hydrolysis were compared in young and elderly subjects following single and multiple doses of spironolactone. After the initial dose on Day 1, plasma levels of canrenone and 'total metabolites' were higher in the young than in the elderly group, and significant differences were found between the two age groups in the AUC for both canrenone and 'total metabolites'. However, these differences between the two age groups diminished after multiple dosing on Day 8, and the steady state pre-dose plasma levels of canrenone and 'total metabolites' were significantly higher in the elderly subjects. The accumulation ratios of canrenone and 'total metabolites' were significantly higher in the elderly than in the young subjects. Both canrenone and canrenoic acid were extensively bound to plasma protein, but no differences were found between the two age groups in protein binding. Observed differences in plasma levels after single and multiple dosing between young and old subjects may be consequences of many factors such as a proportionate shift in metabolism with age; impaired oral absorption of the parent compound; and/or altered volume of distribution of the drug.

Steady-state plasma levels of canrenone have been examined in 23 healthy men who received repeated doses of spironolactone for 15 days. The dose regimens were 200 mg once a day and 50 mg 4 times a day. With both treatments the steady-state levels were reached after 3 to 4 days. With once-a-day treatment, the maximum and minimum steady-state levels were about 500 and 100 ng/ml, respectively. The minimum levels with treatment 4 times a day were about 200 ng/ml. The post steady-state half-life of canrenone with once-a-day treatment (19.2 +/- 6.57 hr) was longer (p less than 0.01) than the half-life obtained in the 4 times-a-day treatment (12.5 +/- 3.39 hr). The former half-life was similar to the log-linear phase half-life of canrenone in the single-dose studies.

Plasma levels of canrenone and androgen receptor-active materials (ARM) were determined during long-term oral K-canrenoate or spironolactone therapy in cirrhotics with chronic recurrent ascites. Mean plasma canrenone level was approximately 3 times higher under K-canrenoate than under spironolactone treatment; moreover, the levels were not dose related. Either type of treatment did not affect plasma aldosterone and testosterone concentrations. Plasma ARM during K-canrenoate treatment did not change, whereas in the spironolactone group a 3-fold increase of ARM occurred (p less than 0.05). No dose-related effect was evident with the latter treatment. The lower incidence of gynecomastia in the K-canrenoate group was not correlated with values of plasma canrenone or ARM (p greater than 0.05). Our study questions the traditional view that the mode of action of spironolactone is via its metabolite canrenone. The two antialdosterone drugs, although equally effective in clearing ascites from cirrhotics, appear to act through partially different metabolites. The lower incidence of antiandrogenic or estrogen-like side effects during K-canrenoate seems to be related to metabolites other than canrenone itself.

The influence of food intake on the bioavailability of canrenone, the major and active metabolite of spironolactone, was explored in 8 healthy male volunteers. Spironolactone was administered as a single oral dose of 100 mg, both in the fasting state and together with a standardized breakfast. Numerous venous blood samples were taken from 30 min to 96 hr after ingestion of the drug, and the plasma concentrations of canrenone were determined by spectrofluorometry. The results indicate that more canrenone enters the general circulation when spironolactone in ingested together with a meal.

A method for the determination of 6,17-dimethylpregna-4,6-diene-3,20-dione (medrogestone) in serum is described using high-pressure liquid chromatography with UV detection. Interfering substances in human or dog serum blanks were removed selectively by reaction with oxalyl chloride followed by an aqueous alkaline borate "wash" of the extract. The method is specific for medrogestone and, based on 5 ml serum, has a limit of detection of 2 ng/ml.

The relative bioavailability of 100 mg canrenone capsules and the commercial 50 mg capsules has been determined in 12 healthy male subjects. The study was conducted in a cross over design. After the absorption phase canrenone plasma concentrations followed a biexponential decay. The half lives of the three phases observed were respectively 40.7 +/- 21.7 min, 1.94 +/- 0.558 hr and 18.5 +/- 3.93 hr after administration of a 100 mg capsules; they were respectively 31.8 +/- 14 min, 1.64 +/- 0.513 hr and 16.1 +/- 3.09 hr after administration of two 50 mg capsules. These values were similar to those reported in man. Bioequivalence of the two forms tested was ascertained by a two way analysis of variance and by the Westlake symmetrical confidence interval (95%). Peak plasma levels, Cmax, time to reach the peak, tmax, and the rate constant of absorption showed great inter and intra individual variations. In vivo hydrolysis of canrenone into canrenoic acid and subsequent lactonization of the acid are pH-dependent and could give rise to these variations if occurring before absorption.