Detection of synthetic corticosteroid analogues by the competitive protein-binding radioassay

Adverse reaction to prednisone in a patient with systemic lupus erythematosus

Oral corticosteroids are the main therapeutic choice for systemic lupus erythematosus (SLE). Adverse reactions to systemic corticosteroids rarely occur and the etiology is unclear in most cases. A 14-year-old girl with newly diagnosed SLE developed a pruritic bullous eruption while on prednisone. The patient had been treated successfully in the hospital with intravenous methylprednisolone. In preparation for discharge, the steroid preparation was changed to prednisone to which the patient reacted with a development of new crops of bullous lesions. Skin biopsy specimens of lesional areas showed a bullous eruption consistent with erythema multiforme. The patient underwent immediate and delayed hypersensitivity tests. Intradermal and patch tests to liquid prednisone were positive. The patient was discharged on oral methylprednisolone and has not had recurrence of the skin lesions. In conclusion, a case of prednisone sensitivity in a patient with SLE is presented here. An alternative preparation, methylprednisolone, was used to successfully treat her underlying condition.

A sensitive radioimmunoassay for fludrocortisone in human plasma

Fludrocortisone has been a mainstay of therapy for orthostatic hypotension for many years. Clinical experience suggests that there exists a substantial interindividual variation in responsiveness to the drug. To assess this, we have developed an assay that permits measurement of the low concentrations of fludrocortisone found in human plasma. Fludrocortisone was detected by radioimmunoassay. A polyclonal rabbit antibody, raised against dexamethasone which cross-reacts strongly with fludrocortisone, was reacted with either standard or unknown samples in the presence of [125I]fludrocortisone-3-TyrNH2 (synthesized by coupling tyrosine amide to fludrocortisone-3-oxime and iodinating with chloramine T oxidation). The ED10, ED50, and ED80 were 0.34, 5.0, and 30 ng/mL of plasma, respectively. The cross reactivity with other 9-fluorinated steroids was found as follows: dexamethasone, 340%; betamethasone, 230%; and triamicinolone, 8%. To preclude an erroneous result, subjects who were pregnant or receiving any steroid medication were excluded from the study. The percent cross-reactivity with the main naturally occurring steroids was as follows: 11-desoxycortisol 3.2%, cortisol 1.1%, DOC 0.3%, pregnenolone 0.1%, corticosterone 0.06%, progesterone 0.05%, and aldosterone < 0.05%. The only compound with potential for interference, because of its high level in the circulation in the early morning, was cortisol.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the biopotency of corticosterone and dexamethasone acetate in glucocorticoid receptor down regulation in rat liver

The effects of long treatment with dexamethasone 21-acetate and corticosterone on the glucocorticoid receptor in rat liver cytosol were compared. Dexamethasone acetate (5 micrograms/ml or 10 micrograms/ml water) or corticosterone (100 micrograms/ml water) was given to adrenalectomized animals as drinking solution for 6 days, and glucocorticoid receptor concentration was determined at 0, 12, 24, 48 and 72 h after steroid withdrawal. Dexamethasone acetate caused a dose dependent depletion of cytosol receptor. There was no measurable binding at time 0; the values of Bmax for the glucocorticoid receptor with decreased at 12, 24 and 48 h after the steroid withdrawal. Increased dissociation constant (Kd) were calculated for 12 and 24 h samples. The effect of corticosterone on receptor depletion was less pronounced. Bmax for the receptor was decreased at 0, 12, 24 h after steroid withdrawal with no change in Kd. The extent of steroids-induced receptor depletion showed good correlation with the induction of tyrosine aminotransferase (TAT), however, maximum TAT activity measured immediately after withdrawal of dexamethasone acetate was lower than that found after a single injection of dexamethasone acetate. We conclude that both steroids cause down regulation of the glucocorticoid receptor in rat liver cytosol, with both the extent and the duration of depletion being dependent on the biopotency of the glucocorticoid.

[Pharmacokinetics of prednisolone in adrenal insufficiency ]

Prednisolone was measured in serum and urine after oral and intravenous administration of prednisone and prednisolone in 16 patients with adrenal insufficiency and after bilateral adrenalectomy. Thus, the problem of cross-reactivity with endogenous steroids, the main factor disturbing the measurement of prednisolone, was completely eliminated. Prednisolone was detected by a simple competitive protein-binding radioassay. Distribution, elimination and other bioavailability parameters were calculated from the obtained data. No significant differences between serum levels were detected after oral administration of these drugs. Peak levels were reached after 2-3 h. After 5, 7.5 and 10 mg prednisone peak serum levels averaged 11.9 +/- 2.2, 15.9+/-3.4 and 21.5+/-5.9 microgram/dl, respectively. Prednisolone was still detectable 24 h after administration of 10 mg. The plasma half-time of approximately 5 1/2 h suggests that prednisolone is present in serum far about 2 days after application of higher doses. Since prednisolone interferes in most assays for cortisol, prednisone therapie has to be stopped at least 2 days before cortisol determinations. Urinary excretion was proportional to the applicated doses. The metabolic clearance rate of prednisolone was decreased (56.0+/-7.2 1/24 h/m2) in patients with adrenal insufficiency. This can be attributed to alterations in corticosteroid metabolism, probably due to an increased transcortin production.

Plasma prednisolone concentrations: comparison of radioimmunoassay and competitive protein binding assay

A comparison was made between plasma concentrations of prednisolone measured by both competitive protein binding radioassay (CPB) and radioimmunoassay (RIA) and, with each assay, using a calibration curve generated from individual subject data and from pooling the individual calibration curva data. The plasma samples were obtained from six normal adult male volunteers who were pretreated with dexamethasone to suppress endogenous hydrocortisone and who then ingested 10 mg of prednisolone. Both the standard curve data and the plasma concentrations were evaluated statistically. It was shown that the CPB method has considerably greater precision than the RIA method and could be employed in bioavailability and pharmacokinetic studies of both prednisolone and prednisone. It was also shown that corticosteroid binding globulin cross-reacts considerably less with the major metabolite of prednisolone, 20beta-dihydroprednisolone, than the particular antiserum used in the RIA.

Relative competition of corticosterone, cortisol, cortisone, 11-dexycortisol and prednisolone with (1,2-3H)-cortisol in various protein-binding radioassay systems

The relative influence of some endogenous corticosteroids and of synthetic prednisolone on competitive protein-binding radioassay was compared with that of cortisol, using as a source of transcortin pooled plasmas from various species and at different dilutions. Human (different clinical situations), cow, dog, sheep, hog, rabbit and chicken plasma were examined. The ability of corticosterone, cortisone, 11-deoxycortisol and prednisolone to displace [1,2-3-H] cortisol from corticosteroid-binding globulin (CBG) was measured: (1) by assessing the amounts (ng/tube) which produce a displacement equal to 10 ng/tube of cortisol, and (2) by calculating the integrated areas of displacement defined by the binding curves and by expressing them as a percentage of the cortisol curve area. While corticosterone, 11-deoxycortisol and prednisolone have a binding potency not very different from that of cortisol in almost the entire set of competitive protein-binding assays tested, the binding ability of cortisone was found to be particularly dependent upon the species of diluted plasma. Differences in the relative specificity of binding are apparent also within the human species, depending on the source of diluted plasma, whereas the concentration of endogenous steroids does not seem to significantly affect binding curves under the conditions examined. It is suggested that binding proteins in various conditions differ from those of healthy adults not only quantitatively but also qualitatively.