Corticosteroid analysis in biological fluids by high-performance liquid chromatography

Fifty Years of Unraveling the Clinical Pharmacology of Corticosteroids

This review will highlight portions of Dr. William Jusko's and colleagues' work that affected the clinical use and study of corticosteroids in acute and chronic disease management. Selected publications related to corticosteroid pharmacokinetics and pharmacodynamics from the 1970s through today were included in this review, with a focus on the foundational human-based studies conducted in the 1970s-1990s. Dr. Jusko contributed significantly to early corticosteroid pharmacology across several domains including: 1) foundational corticosteroid pharmacokinetic methods and parameter development, 2) disease state-variation in corticosteroid pharmacokinetics, 3) drug interaction effects on corticosteroid pharmacokinetics, and 4) early corticosteroid pharmacodynamic studies. In an era where little was known about the pharmacokinetics and pharmacodynamics of corticosteroids, Dr. Jusko's work opened the eyes of researchers and clinicians to the potential for disease and drug interactions that could reduce or enhance the effects of corticosteroids. This significant body of work paved the way for alternative routes of administration that would be useful in concentrating the activity at the site of action and markedly reduced systemic drug exposure, minimizing the risk of adverse effects through application of the dose-sparing pharmacokinetic and pharmacodynamic principles.

The Physiological and Pharmacological Significance of the Circadian Timing of the HPA Axis: A Mathematical Modeling Approach

As a potent endogenous regulator of homeostasis, the circadian time-keeping system synchronizes internal physiology to periodic changes in the external environment to enhance survival. Adapting endogenous rhythms to the external time is accomplished hierarchically with the central pacemaker located in the suprachiasmatic nucleus (SCN) signaling the hypothalamus-pituitary-adrenal (HPA) axis to release hormones, notably cortisol, which help maintain the body's circadian rhythm. Given the essential role of HPA-releasing hormones in regulating physiological functions, including immune response, cell cycle, and energy metabolism, their daily variation is critical for the proper function of the circadian timing system. In this review, we focus on cortisol and key fundamental properties of the HPA axis and highlight their importance in controlling circadian dynamics. We demonstrate how systems-driven, mathematical modeling of the HPA axis complements experimental findings, enhances our understanding of complex physiological systems, helps predict potential mechanisms of action, and elucidates the consequences of circadian disruption. Finally, we outline the implications of circadian regulation in the context of personalized chronotherapy. Focusing on the chrono-pharmacology of synthetic glucocorticoids, we review the challenges and opportunities associated with moving toward personalized therapies that capitalize on circadian rhythms.

Transitioning from Basic toward Systems Pharmacodynamic Models: Lessons from Corticosteroids

Technology in bioanalysis, -omics, and computation have evolved over the past half century to allow for comprehensive assessments of the molecular to whole body pharmacology of diverse corticosteroids. Such studies have advanced pharmacokinetic and pharmacodynamic (PK/PD) concepts and models that often generalize across various classes of drugs. These models encompass the "pillars" of pharmacology, namely PK and target drug exposure, the mass-law interactions of drugs with receptors/targets, and the consequent turnover and homeostatic control of genes, biomarkers, physiologic responses, and disease symptoms. Pharmacokinetic methodology utilizes noncompartmental, compartmental, reversible, physiologic [full physiologically based pharmacokinetic (PBPK) and minimal PBPK], and target-mediated drug disposition models using a growing array of pharmacometric considerations and software. Basic PK/PD models have emerged (simple direct, biophase, slow receptor binding, indirect response, irreversible, turnover with inactivation, and transduction models) that place emphasis on parsimony, are mechanistic in nature, and serve as highly useful "top-down" methods of quantitating the actions of diverse drugs. These are often components of more complex quantitative systems pharmacology (QSP) models that explain the array of responses to various drugs, including corticosteroids. Progressively deeper mechanistic appreciation of PBPK, drug-target interactions, and systems physiology from the molecular (genomic, proteomic, metabolomic) to cellular to whole body levels provides the foundation for enhanced PK/PD to comprehensive QSP models. Our research based on cell, animal, clinical, and theoretical studies with corticosteroids have provided ideas and quantitative methods that have broadly advanced the fields of PK/PD and QSP modeling and illustrates the transition toward a global, systems understanding of actions of diverse drugs. SIGNIFICANCE STATEMENT: Over the past half century, pharmacokinetics (PK) and pharmacokinetics/pharmacodynamics (PK/PD) have evolved to provide an array of mechanism-based models that help quantitate the disposition and actions of most drugs. We describe how many basic PK and PK/PD model components were identified and often applied to the diverse properties of corticosteroids (CS). The CS have complications in disposition and a wide array of simple receptor-to complex gene-mediated actions in multiple organs. Continued assessments of such complexities have offered opportunities to develop models ranging from simple PK to enhanced PK/PD to quantitative systems pharmacology (QSP) that help explain therapeutic and adverse CS effects. Concurrent development of state-of-the-art PK, PK/PD, and QSP models are described alongside experimental studies that revealed diverse CS actions.

Nebulization of Cyclic Arginine-Glycine-(D)-Aspartic Acid-Peptide Grafted and Drug Encapsulated Liposomes for Inhibition of Acute Lung Injury

PURPOSE

Acute lung injury (ALI) is a fatal syndrome in critically ill patients. It is characterized by lung edema and inflammation. Numerous pro-inflammatory mediators are released into alveoli. Among them, interleukin-1beta (IL-1β) causes an increase in solute permeability across the alveolar-capillary barrier leading to edema. It activates key effector cells (alveolar epithelial and endothelial cells) releasing inflammatory chemokines and cytokines. The purpose of the study was to demonstrate that nebulized liposomes inhibit ALI in vivo.

METHODS

In vivo ALI model was simulated through intra-tracheal instillation of IL-1β solution (100 μg/mL in PBS, pH 7.2, 200 μL) in male Sprague-Dawley rats. Various formulations were tested in ALI induced rats. These formulations include plain liposomes (PL), methylprednisolone sodium succinate solution (MPS solution), cRGD-peptide grafted liposomes (L^cRGD) and methylprednisolone sodium succinate encapsulated and cRGD-peptide grafted liposomes (MPS-L^cRGD). Formulations were nebulized in vivo in rats using micro-pump nebulizer.

RESULTS

Liposome formulations exhibited higher levels of drug concentration in lungs. The physicochemical parameters demonstrated that the liposome formulations were stable. On the basis of aerodynamic droplet-size, nebulized formulations were estimated to deposit in different regions of respiratory tract, especially alveolar region, Among the formulations, MPS-L^cRGD caused significant reduction of edema, neutrophil infiltration and inflammation biochemical marker levels.

CONCLUSION

From the results, it can be inferred that nebulization of targeted liposomes had facilitated spatial and temporal modulation of drug delivery resulting in alleviation of ALI.

Estimation of minimum whole-blood tacrolimus concentration for therapeutic drug monitoring with plasma prednisolone concentration: A retrospective cohort study in Japanese kidney transplant recipients

BACKGROUND

In immunosuppressive therapy administered after organ transplantation, therapeutic drug monitoring (TDM) of tacrolimus must be performed frequently because of the large variation in its pharmacokinetic properties and a progressive decrease in dose requirements. An indicator for estimating the target minimum whole-blood tacrolimus concentration (Cmin TAC) would be useful to minimize the number of blood samplings required for tacrolimus TDM.

OBJECTIVES

The primary objective of this study was to investigate whether plasma prednisolone concentration, postoperative days (POD) and AUC 0 to 9 hours before transplantation (AUC0-9int) are useful indicators of tacrolimus TDM. The secondary objective was to determine the usefulness of blood tacrolimus concentration as an indicator of the development of nontraumatic, glucocorticoid-induced necrosis of the femoral head, an adverse event that has been associated with the use of prednisolone in vivo.

METHODS

This open-label, nonrandomized, retrospective study was conducted at the Department of Transplantation and Regenerative Surgery, Kyoto Prefectural University of Medicine, Kyoto, Japan. Data from 43 male and 22 female patients (mean age, 38 years [range, 9-64 years]) who received a living-related kidney transplant from 2001 to 2004 were included. Multiple blood samplings were performed to determine AUC0-9int, AUC 0 to 9 hours after drug administration and after transplantation (AUC0-9), Cmin TAC, Cmax, and Tmax after transplantation. The correlations between each parameter were determined. The correlation between POD and the changes in tacrolimus bioavailability was investigated using the indicator, defined as the tacrolimus dose required to maintain the target (10-15 ng/mL) Cmin TAC (dose/C10-15). Correlations between dose/C10-15 and AUC0-9int (3 AUC0-9int groups, defined as follows: low, medium, and high [<93, ≧93-≤152, and ≧152 ng·h/mL, respectively]) were determined. Correlations between mean Cmin values of prednisolone at a dose of 40 mg on PODs 4 to 11 (Cmin PSL40) and Cmin TAC, or AUC0-9int were determined. A subanalysis was used to determine the relationship between dose/C10-15 and the prevalence of nontraumatic, glucocorticoid-induced necrosis of the femoral head.

RESULTS

Cmin TAC was found to be significantly correlated with AUC0-9int (r=0.554; P<0.001) and Cmin PSL40 (r=0.336; P<0.001). In the low-AUC0-9int group, dose/C10-15 was higher than that of the other groups (P<0.001). AUC0-9int was significantly correlated with Cmin PSL40 (r=0.445; P<0.001)). Dose/C10-15 in the patient group that had necrosis of the femoral head was lower than that of the group without necrosis (n=6; P<0.01).

CONCLUSIONS

The results of this small, retrospective study suggest that Cmin PSL40, AUC0-9int, and POD were significant predictors of Cmin TAC. These parameters were found to be a useful indicator of tacrolimus TDM in these Japanese transplant recipients. Our results also suggest that dose/C10-15 and AUC0-9int might be useful indicators for estimating the risk for nontraumatic, steroid-induced necrosis of the femoral head. (Curr Ther Res Clin Exp. 2006;67: 103-117) Copyright © 2006 Excerpta Medica, Inc.

Stress hormone concentration in Rocky Mountain populations of the American pika (Ochotona princeps)

The American pika (Ochotona princeps) is considered a sentinel species for detecting ecological effects of climate change. Pikas are declining within a large portion of their range, but previous studies have focused only on local pika extinction as a metric of change. We designed a procedure which can provide an earlier warning signal, based on non-invasive sampling and analysis of physiological stress in living pikas. Pikas were sampled at several locations in the Rocky Mountains for the measurement of glucocorticoid metabolites (GCMs) in faeces. Using a time series of faecal pellets from 12 individuals, we detected a significant increase in faecal GCM level in response to capture, thus biologically validating the use of a corticosterone enzyme immunoassay. We also established baseline, peak, and post-peak GCM concentrations for pikas in the Rocky Mountains, which varied according to gender and individual. This is the first study to measure stress hormone metabolites in any species of pika. The methods developed and validated in this study can be used to add non-invasive measurements of physiological stress to pika monitoring programmes and other research designed to assess pika vulnerability to predicted changes in climate. Pika monitoring programmes currently in place use a protocol that relates current site use by pikas with data on local habitat characteristics, such as elevation, to infer potential effects of climate change. Data generated by these monitoring studies can be used to identify the trends in site use by pikas in relationship to habitat covariates. However, this approach does not take into account the role of behavioural thermoregulation and the pika's use of microhabitats to ameliorate variations in climate. Incorporating a stress metric, such as GCM concentration, will provide relatively direct evidence for or against the hypothesis that pikas can be stressed by climate regardless of behavioural adaptations.

Dose Equivalency Evaluation of Major Corticosteroids: Pharmacokinetics and Cell Trafficking and Cortisol Dynamics

The integrity of current corticosteroid dose equivalency tables, as assessed by mechanistic models for cell trafficking and cortisol dynamics, was investigated in this study. Single, presumably equivalent, doses of intravenous hydrocortisone, methylprednisolone, dexamethasone, and oral prednisolone were given to 5 white men, according to total body weight, in a 5-way crossover, placebo-controlled study. Pharmacodynamic (PD) response-time profiles for T helper cells, T suppressor cells, neutrophils, and adrenal suppression were evaluated by extended indirect response models. For adrenal suppression, prednisolone appears to be less potent than methylprednisolone or dexamethasone. A good correlation was found between the estimated in vivo EC50 values and relative receptor affinity (equilibrium dissociation constants normalized to dexamethasone). Area under the effect curves of all PD responses was calculated using a linear-trapezoidal method. Although T helper cell trafficking and adrenal suppression achieved significant differences by repeated-measures ANOVA (p = 0.014 and 0.022), post hoc analysis using the Bonferroni method revealed no difference between treatments. Although limited by the use of single doses and a relatively small sample size, this study applies mechanistic models for several biomarkers showing that currently used dosing tables reflect reasonable dose equivalency relationships for four corticosteroids.

Influence of dialysis on prednisolone kinetics

Six patients with end-stage renal disease were given prednisolone, 0.7-1.0 mg/kg/b.wt. parenterally. Prednisolone kinetics were investigated during dialysis, in 3 patients on hemodialysis and in 3 on continuous peritoneal dialysis, and also on days without dialysis. Mean plasma half-life was 250 min in five patients and 690 min in one patient who also suffered from intermittent porphyria. No change was found in prednisolone kinetics when the dialysis-free period was compared to the dialysis periods.

Simple liquid chromatography method for the rapid simultaneous determination of prednisolone and cortisol in plasma and urine using hydrophilic lipophilic balanced solid phase extraction cartridges

This article describes the development and validation of a simple solid phase extraction (SPE) and HPLC method for the extraction and the specific determination of prednisolone and hydrocortisone (cortisol) in both plasma and urine using one washing step with Oasis hydrophilic lipophilic balanced (HLB) cartridges (1 ml/30 mg, 30 microm). Recoveries of prednisolone and cortisol from plasma and urine exceeded 82%. The limit of quantification (LOQ) in plasma and urine was 9.9 and 6.7 ng/ml for cortisol, respectively, and 11.6 and 8.0 ng/ml for prednisolone, respectively. The intraday and interday precision (measured by CV%) for both prednisolone and cortisol in both plasma and urine was always less than 7%. The accuracy (measured by relative error %) for both prednisolone and cortisol in both plasma and urine was always less than 8%. The advantages of the developed method are the use of a one step washing SPE utilising HLB cartridges which do not suffer the drying out problems of conventional SPE cartridges and the time saving when compared with solvent extraction (SE), in addition to the simultaneous determination of prednisolone and cortisol in both plasma and urine.

Methylprednisolone sodium succinate in pediatric parenteral nutrition: influence of vehicle injection

Many drugs can be administered in parenteral nutrient mixtures, but no work on the delivery of corticoids by such means is reported. We studied the influence of pediatric parenteral nutrient mixtures on the kinetic parameters of the corticoid methylprednisolone injected in an intravenous bolus in rabbits as its sodium succinate ester. Four groups of six male New Zealand rabbits were used. After extraction, the plasma drug concentrations were measured by high performance liquid chromatography. The distribution volume of the ester and the clearance rates of the two entities (ester and methylprednisolone) were lowered in the presence of a lipid emulsion. The description of these pharmacokinetic parameters provides a basis for a preclinical study of 24h administration of methylprednisolone in a parenteral nutrient mixture.

Pharmacokinetic/pharmacodynamic modelling of effects of dexamethasone and prednisolone in combination with endogenous cortisol on lymphocyte counts and systemic markers of bone turn over and inflammation in healthy and asthmatic men

OBJECTIVE

To compare potency and efficacy of dexamethasone (DEXA) and prednisolone (PRED) in assumed equipotent doses in combination with endogenous cortisol, using lymphocyte counts, plasma osteocalcin (OC), and eosinophilic cationic protein (ECP) as effect variables and to evaluate potential differences between healthy subjects and asthmatic patients.

METHODS

Eight healthy subjects and six asthmatic patients who had stopped taking their regular inhaled glucocorticosteroid treatment (ICS) for 1 week, were given an IV bolus of DEXA and PRED in assumed equipotent doses of 2.0 mg and 12.5 mg, respectively, on separate occasions, in combination with subcutaneously injected granulocyte-colony-stimulating factor (G-CSF) as a stimulant for ECP production. Plasma levels of DEXA, PRED, cortisol and effect variables were determined over 25 h and pharmacokinetic-pharmacodynamic (PK-PD) modelling was performed.

RESULTS

Baseline cortisol concentration was lower in patients than in healthy subjects. Both of the exogenous glucocorticoids (GCs) diminished cortisol production. In the healthy subjects, the cortisol production remained suppressed for the full duration of the study day after DEXA but not after PRED. In the asthmatic patients though, the reappearance of the endogenous production of cortisol was seen after both DEXA and PRED. The E(max) values for lymphocyte counts and OC showed that cortisol acted as partial, and DEXA and PRED as full agonists. The observed responses of DEXA and PRED suppressing cortisol, OC and lymphocyte counts were all of the same relative order of magnitude, in accordance with the estimated PD parameters. However, cortisol was estimated to have very little effect on ECP and modelling further predicted that DEXA and PRED were only partial agonists for this effect, without a difference between healthy and asthmatic subjects. Yet, in healthy subjects, the area under the concentration-time curves (AUCs) indicated unexpectedly that ECP was only suppressed after PRED and not after DEXA, while in patients it was suppressed after both GCs. The rank order of potency on lymphocyte counts, OC and ECP was DEXA>PRED>cortisol, although the different relative potencies of the three GCs involved were not the same for all of the three effect variables and differences were also found between healthy and asthmatic subjects.

CONCLUSION

PK-PD modelling studies of GCs demonstrated not only differences in potency of DEXA and PRED on the measured systemic markers, but also different potencies per target tissue and differences between healthy and asthmatic men. The effects caused by the achieved blood concentrations of DEXA and PRED, expressed as AUCs of the effect variables, were in accordance with their respective E(max) values in case of the lymphocytes and OC but not for ECP.

Lack of a Fluoxetine Effect on Prednisolone Disposition and Cortisol Suppression

STUDY OBJECTIVE

To evaluate the potential effect of fluoxetine, a cytochrome P450 isoenzyme inhibitor, on prednisolone disposition and cortisol suppression.

DESIGN

Sequential, two-phase, crossover, open-label pharmacokinetic study.

SETTING

General clinical research center.

SUBJECTS

Fourteen healthy volunteers.

INTERVENTION

A single intravenous dose of prednisolone 40 mg before and after 14 days of treatment with fluoxetine 20 mg/day for 5 days followed by 60 mg/day for 9 days to achieve steady-state concentrations.

MEASUREMENTS AND MAIN RESULTS

Pharmacokinetic parameters of the prednisolone and resulting pharmacodynamic effects on the time course of plasma cortisol suppression before and after fluoxetine administration were evaluated. No significant differences were observed for the mean +/- SD area under the prednisolone concentration-time curve (3739 +/- 992 vs 3498 +/- 797 microg x hr/L, respectively), clearance (8.58 +/- 2.62 vs 8.92 +/- 2.05 L/hr, respectively), volume of distribution (39.5 +/- 12.4 vs 38.2 +/- 9.9 L, respectively), elimination half-life (3.32 +/- 0.83 vs 3.05 +/- 0.80 hrs, respectively), or duration of plasma cortisol suppression (23.5 +/- 3.1 vs 22.0 +/- 4.2 hrs, respectively).

CONCLUSION

Fluoxetine administration did not significantly affect prednisolone disposition or prolong cortisol suppression. This finding suggests that coadministration of these agents is unlikely to result in clinically important pharmacokinetic or pharmacodynamic drug interactions. Prednisolone may be a useful alternative for patients who require both glucocorticoid and fluoxetine therapy.

Pharmacokinetic/pharmacodynamic model for prednisolone inhibition of whole blood lymphocyte proliferation

AIMS

Mitogen-induced ex vivo whole blood lymphocyte proliferation (WBLP) is a widely used method to assess lymphocyte responsiveness to immunosuppressive therapy. A three-component complex model was developed to characterize effects of prednisolone on cell trafficking, transduction, and lymphocyte suppression.

METHODS

An oral dose (0.27 mg kg-1) of prednisone was given to 32 subjects. The study consisted of baseline and prednisone phases each with 32 h of sampling. Measurements included plasma prednisolone concentrations, in vitro and ex vivo WBLP, and lymphocyte cell counts during baseline and prednisone phases.

RESULTS

The final model consists of a precursor-dependent indirect response model with a first-order periodic influx rate for lymphocyte trafficking. This accounts for the rebound phenomenon and the circadian rhythm seen in all individual ex vivo WBLP effect-time profiles. Prednisolone was modelled as inhibiting lymphocyte influx from the precursor to the blood pools. The direct suppressive effect of prednisolone on WBLP was modelled with the simple Imax model. A transduction step with rate constant kt was introduced to the simple Imax model to account for the delay ( approximately 4 h) in reaching the maximum inhibition. The IC50 values obtained ex vivo were circa 10 times lower than in vitro values (3.76 vs 38.8 ng ml-1), suggesting additional in vivo factors may have enhanced lymphocyte response to the inhibitory effect of prednisolone.

CONCLUSIONS

This integrated PK/PD model enables evaluation of multicomponent direct and indirect inhibition of ex vivo WBLP by steroids and other immunosuppressants in relation to sex and race.

Prednisolone pharmacokinetics and pharmacodynamics in relation to sex and race

Prednisolone pharmacokinetics (PK) and pharmacodynamics (PD) were investigated in relation to sex and race in white males, black males, white females, and black females (n = 8/group) after a single oral dose (0.27 mg/kg) of prednisone. The study consisted of baseline and prednisone phases with 32-hour sampling in each phase. Women were studied during the luteal phase of their menstrual cycle. Total and free plasma prednisolone concentrations were assayed by HPLC and ultrafiltration, and pharmacokinetic data were analyzed by compartmental fitting using WinNonlin. Plasma cortisol concentrations were assayed by HPLC; T-helper, T-suppressor lymphocyte, and neutrophil cell counts were determined by FACS and hemocytometry, and these pharmacodynamic data were evaluated by basic and extended indirect response models using ADAPT II. Total body weight-normalized free prednisolone oral clearance and apparent volume of distribution were higher in men compared with women, regardless of race (by 22% in whites and 40% in blacks for oral clearance, p < 0.01; by32% in whites and 38% in blacks for apparent volume of distribution, p < 0.01). The 50% inhibitory concentration (IC50) values for T-suppressor cell-trafficking inhibition were higher in whites than in blacks, regardless of sex (by 125% in men and 208% in women, p < 0.01). The IC50 or SC50 values for effects of prednisolone on cortisol secretion and T-helper lymphocyte or neutrophil trafficking were not statistically different between men and women, blacks and whites. The findings of this study suggest that there are some prednisolone PK/PD differences related to sex and race. However, these differences do not suggest the need for dosage adjustments, and additional experiments with repeat dosing are needed to fully evaluate the clinical implication of these findings.

Effects of oral prasterone (dehydroepiandrosterone) on single-dose pharmacokinetics of oral prednisone and cortisol suppression in normal women

This study sought to determine effects of multiple dosing of prasterone (DHEA, dehydroepiandrosterone) on the pharmacokinetics of prednisolone and endogenous cortisol secretion. These drugs are likely to be coadministered to patients with systemic lupus erythematosus. Fourteen normal women (ages 30.1 +/- 5.4 years) received single-dose oral prednisone (20 mg) before and after 200 mg/day of oral prasterone for one menstrual cycle (approximately 28 days). Identical assessments, timed to onset of menses, were conducted pretreatment (baseline) and at days 28 and 29 of prasterone treatment and included serum total and free prednisolone, prednisone, DHEA, DHEA-S (dehydroepiandrosterone sulfate), ACTH-stimulated cortisol, and sex hormones and 24-hour urine free cortisol. Pharmacokinetic parameters of prednisolone as assessed by Cmax, t 1/2, AUC, or serum protein binding were not affected by prasterone. The ACTH-stimulated plasma cortisol concentrations were mildly reduced, but 24-hour urinefree cortisol excretion was unchanged during prasterone administration. Serum androstenedione and testosterone increased, while no changes in serum estradiol or estrone occurred. The administration of 200 mg oral prasterone produced serum concentrations of DHEA and DHEA-S significantly greater than endogenous levels. Chronic dosing with 200 mg/day of prasterone did not alter either prednisolone pharmacokinetics or inhibition of cortisol secretion by prednisolone.

Simultaneous determination of plasma prednisolone, prednisone, and cortisol levels by high-performance liquid chromatography

Recipients of organ transplants remain particularly dependent on prednisolone as part of their maintenance immunosuppression. Despite this, the pharmacokinetics of prednisolone have never been fully characterized in these patients, and consequently dosing remains empirical. Accurate monitoring of prednisolone, its primary metabolite prednisone, and endogenous cortisol suppression in such patients may provide a means of improving the clinical outcome by adjusting for variability in prednisolone pharmacokinetics and pharmacodynamics. Measurement of endogenous cortisol may provide an independent marker of prednisolone pharmacodynamics. A simple isocratic reverse-phase high-performance liquid chromatography procedure, using betamethasone as an internal standard, was developed to quantify plasma prednisolone, prednisone, and cortisol simultaneously. The steroids were extracted from 0.5 mL plasma with 3 mL (1:1 v/v) ethyl acetate/tert-methyl butyl ether and 0.1 mL phosphoric acid, washed in 0.1 mol/L NaOH before a final drying step and reconstitution in mobile phase for injection. Separation was achieved using a Supelcosil LC-18-DB, 150 x 4.6-mm, 5-microm particle size, reverse-phase column attached to a Newguard 15 x 3-mm, RP8 guard column maintained at 25 degreesC, with ultraviolet detector set at 254 nm. The mobile phase consisted of 16% isopropanol in water containing 0.1% trifluoroacetic acid, set at a flow rate of 1.2 mL/min. The assay was linear up to 1,002 microg/L for prednisolone, 982 microg/L for prednisone, and 545 microg/L for cortisol. Mean intra-assay and interassay imprecision levels were 6.0% and 7.2%, respectively, for prednisolone, 5.8% and 7.2% for prednisone, and 5.6% and 7.9% for cortisol. Intra-assay inaccuracy was <7% of nominal values for prednisolone, prednisone, and cortisol. The lower limit of quantification was 7 microg/L for prednisolone and prednisone and 10 microg/L for cortisol. Corticosteroid recoveries were 73%, 74%, and 90% for prednisolone, prednisone, and cortisol, respectively. The authors describe a robust, inexpensive, and simple method suitable for therapeutic drug monitoring or pharmacokinetic studies of prednisolone; it may also be used to measure the suppression of endogenous cortisol production.

Development of a urinary free cortisol assay using solid-phase extraction-capillary electrophoresis

In clinical practice, the measurement of urinary free cortisol (UFC) provides the most sensitive and specific diagnostic information for excess adrenal production of cortisol. The existing methodologies (RIA and HPLC) are time consuming, costly, involve tedious extractions, derivatizations and problems with non-specific interactions with cortisol metabolites in urine. In the present study, we describe the development of an SPE-CE method for the rapid analysis of UFC. UFC was concentrated using SPE C18 cartridges (3M Empore) under a vacuum and eluted with acetonitrile-SDS. The use of 10% acetone to wash cartridges before final elution with acetonitrile-SDS showed significant improvements in the free cortisol recovery. The complete extraction was accomplished in 10-15 min with a recovery of 89-94%. CE analysis was done on a Beckman P/ACE 5010 with detection at 254 nm using a neutral capillary. Detection limits of free cortisol in urine was improved to 10 microg/l with SPE compared to 500 microg/l without SPE. No interferences either from BSA or other urinary cortisol metabolites affected the free cortisol determinations. The results showed the feasibility of a rapid UFC detection with improved sample handling capacity.

Pharmacokinetic and adrenal interactions of IL-10 and prednisone in healthy volunteers

The pharmacokinetic and adrenal interactions of recombinant human interleukin-10 and prednisolone were examined in this open-label, randomized, four-way crossover study in 12 healthy adult male volunteers. Single doses of IL-10 (8 micrograms/kg s.c.), IL-10 with prednisone (15 mg p.o.), placebo with prednisone, or placebo were administered on four separate occasions with at least 3-week interceding washout periods. Measurements included plasma prednisone, prednisolone and cortisol, unbound prednisolone, and serum IL-10 concentrations. Pharmacokinetic parameters were determined using noncompartmental and model-fitting analysis, while area analysis and an indirect response model were used to assess cortisol dynamics. IL-10 exhibited prolonged serum concentrations owing to dual-absorption processes that were largely unaffected by prednisone. The Cmax values were about 3 ng/mL, while the tmax occurred at 7 to 9 hours. Prednisolone exhibited rapid systemic kinetics with a Cmax of 235 ng/mL, tmax at 1.11 hours, and t1/2 of 2.54 hours with no significant alterations owing to IL-10. Both prednisolone and prednisolone/IL-10 caused marked suppression of cortisol concentrations with similar magnitude and IC50 values; however, IL-10 alone significantly increased the 24-hour AUC of cortisol by 20%. Thus, IL-10 and prednisolone do not interact in disposition or adrenal suppression to a clinically significant degree.

Pharmacokinetic and pharmacodynamic interactions between dehydroepiandrosterone and prednisolone in the rat

The effects of multiple-dosing with dehydroepiandrosterone sulfate (DHEA-SO4) on the pharmacokinetics and pharmacodynamics of prednisolone were examined. Prednisolone (25 mg/kg i.v.) was administered to male and female Sprague-Dawley rats (250-350 g) alone and following DHEA-SO4 (4 mg/kg i.v., every 8 h for 4 days). Male control rats cleared prednisolone faster [3.68 +/- 1.30 (males) vs 1.01 +/- 0.7 l/h/kg; p < 0.05] and had larger Vss (1.38 +/- 0.459 vs 0.394 +/- 0.500 l/kg; p < 0.05) than females both due largely to lesser plasma protein binding. Prednisolone clearance and Vss were not altered by DHEA-SO4 in males or females. The net effect of prednisolone on basophils and plasma corticosterone did not differ with gender. DHEA-SO4 had no effect on plasma corticosterone and did not alter prednisolone action. DHEA-SO4 inhibited basophil trafficking in males, but to a lesser extent than prednisolone, and antagonized the effect of prednisolone on basophil trafficking in both sexes. The steroid-sparing effect observed with DHEA clinically may not be due to an alteration of corticosteroid pharmacokinetics but partly to its ability to affect immune functions.

Influence of gender on prednisolone effects on whole blood T-cell deactivation and trafficking in rats

Prednisolone (5 mg/kg intravenous) was administered to adrenalectomized male and female Sprague-Dawley rats (250-350 g) to assess the effects of gender on disposition and pharmacoimmunodynamics. Plasma concentrations of prednisolone were determined by high-performance liquid chromatography. Incorporation of [3H]thymidine (3H-TDR) was used to determine whole blood T-cell (WBTC) trafficking and deactivation following stimulation with Concanavalin-A. Whole blood T-cell trafficking was determined indirectly by using the glucocorticoid receptor antagonist RU-40555 (250 ng/mL) added to ex vivo cultures of whole blood from animals dosed with prednisolone. Mean (+/- SD) prednisolone clearance values were 3.22 +/- 0.88 and 3.46 +/- 0.96 L/h/kg in males and females, respectively. After administration of prednisolone, relative T-cell counts decreased slowly with time to reach a nadir at 3-5 h and returned to baseline levels by 8 h. Fitting data using an indirect response model yielded mean prednisolone 50% inhibitory concentration for inhibition of WBTC trafficking (IC50T) that was lower in males compared with females (0.14 +/- 0.16 versus 1.03 +/- 0.06 ng/mL; p < 0.05). In the absence of RU-40555, an immediate and complete inhibition of 3H-TDR incorporation into WBTC was observed (deactivation) and baseline levels were recovered slowly as prednisolone was cleared from blood. The mean 50% inhibitory concentration for inhibition of WBTC deactivation (IC50D) based on an inhibitory Imax model was similar in males and females (0.20 +/- 0.24 versus 0.18 +/- 0.12 ng/mL). Although male and female rats have similar exposure to prednisolone after 5-mg/kg doses, males are more sensitive to the inhibition of WBTC trafficking, whereas no gender effects on deactivation of WBTC exist.

Serum cortisol in asthma: marker of nocturnal worsening of symptoms and lung function?

Changes in the hormone cortisol have been implicated in the pathogenesis of nocturnal worsening of asthma, or nocturnal asthma (NA). We studied 45 patients, 15 with NA, 15 subjects with non-nocturnal asthma (NNA), and 15 controls over a 24h period, measuring forced expiratory volume in 1 second (FEV1) and serum cortisol at 08:00, 12:00, 16:00, 20:00, 23:00, 04:00, and 08:00 the following day. Evaluation of the time response curves for cortisol revealed a significant difference in the shape of the curves (p = 0.04 by mixed-effects model). Evaluation of individual time points revealed that the cortisol levels in the NNA and control groups were significantly lower than in the NA group at 20:00 (NNA: 3.5 +/- 0.8 mg/mL;

CONTROLS

3.4 +/- 0.8 mg/mL; NA: 4.9 +/- 0.8 mg/mL; p = 0.007). The percentage (%) predicted FEV1 was significantly different among the three groups over the 24h period (p < 0.001). The percentage predicted FEV1 was significantly lower in the NA group compared to the control group at all time points and significantly lower than the NNA group at 16:00, 23:00, and 04:00. The difference among the groups was most pronounced at 04:00, when the percentage predicted FEV1 was 58.9 +/- 2.2% in the NA group, 76.8 +/- 2.9% in the NNA group, and 91.6 +/- 2.8% in the control group (p = 0.001, where each group is significantly different from the others). Although the time response curves for cortisol were significantly different among the three groups, the differences in serum levels of cortisol do not appear to be clinically significant. Therefore, serum levels of cortisol may not be the appropriate measurement to assess the role of cortisol in nocturnal asthma.

Pharmacokinetics of methylprednisolone and prednisolone after single and multiple oral administration

The pharmacokinetics of methylprednisolone and prednisolone were evaluated in 24 healthy men after oral administration of single and multiple doses for 3 days. For each drug, 6 different administration regimens with doses ranging from 1 to 80-mg of methylprednisolone and 1.25 to 100-mg of prednisolone, and administration intervals ranging from 3 to 24 hours for both were investigated. Plasma was assayed using a normal phase high-performance liquid chromatography (HPLC) method. Methylprednisolone showed linear pharmacokinetics with no apparent dose or time dependency. Prednisolone showed marked dose dependency with higher clearance and volume of distribution for higher doses. This can be explained by its saturable protein binding of plasma, because unbound clearance and unbound volume of distribution were not dose-dependent. After multiple administration, prednisolone showed significant time-dependent pharmacokinetics with increased unbound clearance and increased unbound volume of distribution. Due to the complicated pharmacokinetic properties of prednisolone, it is extremely difficult to determine the dose needed to obtain a desired target concentration. The pharmacokinetics of methylprednisolone are more predictable because methylprednisolone concentrations are proportional to dose, and no determination of plasma protein binding is needed.

Pharmacokinetics of prednisolone during administration of sirolimus in patients with renal transplants

The pharmacokinetic interaction of multiple oral doses of sirolimus (rapamycin) and prednisone were evaluated in 40 stable patients with renal transplants receiving concomitant multiple doses of cyclosporine. Nine sirolimus dosage levels from 1 mg/m2/day to 13 mg/m2/day were studied and compared with placebo. Plasma concentrations of prednisone, prednisolone, and cortisol were measured by high-performance liquid chromatography and analyzed by noncompartmental methods. Mean pharmacokinetic values of prednisolone found before sirolimus administration were as follows: peak plasma concentration (Cmax) was 187 ng/mL; time to peak plasma concentration (tmax) was 2.03 hours; rate of reaching peak plasma concentration (Cmax divided by the area under the concentration-time curve [AUC]) was 0.149 hour-1; terminal half-life (t1/2) was 3.60 hours; AUC was 1206 ng.hour/mL; and apparent clearance (Cl/F) was 0.094 L/hour/kg. During the 2 weeks of concomitant administration, prednisolone elimination decreased in relation to sirolimus dosages. These changes were modest, with mean increases of 18% in Cmax and 27% in t1/2 and mean decreases of 27% in Cl/F for the groups receiving 6 mg/m2/day to 13 mg/m2/day. Most patients initially had plasma cortisol concentrations indicative of adrenal suppression. With sirolimus treatment, the Cmax of cortisol did not decrease further, but the AUC (8:00 AM-8:00 PM) values were significantly lower, independent of sirolimus exposure. The AUC for cyclosporine did not correlate with sirolimus and prednisolone exposure. A 2-week course of sirolimus showed a slight pharmacokinetic interaction between sirolimus and prednisolone/prednisone/cortisol in stable patients with renal transplants.

Simultaneous determination of prednisolone, prednisolone acetate and hydrocortisone in human serum by high-performance liquid chromatography

A method for the simultaneous determination of prednisolone, prednisolone acetate and hydrocortisone has been established to monitor the serum levels of these three compounds in healthy volunteers following intramuscular administration of prednisolone acetate. Serum samples of 0.75 ml were extracted with ethyl acetate after addition of the internal standard, dexamethasone. The compounds were separated using a LiChrosorb Si 60 column and detected by UV absorbance. Specificity, linearity, as well as the repeatability, intermediate-precision and accuracy of the method were established. The lower limit of quantification was 20 ng/ml for prednisolone (C.V. = 14.7%, n = 6) and 5.0 ng/ml for prednisolone acetate (C.V. = 13.9%, n = 6) and hydrocortisone (C.V. = 11.7%, n = 6). Data on the recovery of the compounds and the internal standard are provided. The results of quality control samples determined during routine analysis (n = 114) are presented. Serum levels of the compounds after intramuscular administration of 25 mg of prednisolone acetate are discussed.

Pharmacokinetic/pharmacodynamic evaluation of deflazacort in comparison to methylprednisolone and prednisolone

PURPOSE

The pharmacokinetics and pharmacodynamics of deflazacort after oral administration (30 mg) to healthy volunteers were determined and compared with those of 20 mg of methylprednisolone and 25 mg of prednisolone.

METHODS

Methylprednisolone, prednisolone and the active metabolite of deflazacort, 21-desacetyldeflazacort, were measured in plasma using HPLC. For the assessment of pharmacodynamics, differential white blood cell counts were obtained over 24 hours. An integrated pharmacokinetic-pharmacodynamic (PK-PD) model was applied to link corticosteroid concentrations to the effect on lymphocytes and granulocytes.

RESULTS

Deflazacort is an inactive prodrug which is converted rapidly to the active metabolite 21-desacetyldeflazacort. Maximum concentrations of 21-desacetyldeflazacort averaged 116 ng/ml and were observed after 1.3 h. The average area under the curve was 280 ng/ml.h, and the terminal half-life was 1.3 h. 21-Desacetyldeflazacort was cleared significantly faster than both methylprednisolone and prednisolone. The PK-PD-model was suitable to describe time course and magnitude of the observed effects. The results were consistent with reported values for glucocorticoid receptor binding affinities for the investigated compounds.

CONCLUSIONS

Due to the short pharmacokinetic half-life of its active metabolite, pharmacodynamic effects of deflazacort are of shorter duration than those of methylprednisolone and prednisolone. The PK-PD model allows good prediction of pharmacodynamic effects based on pharmacokinetic and receptor binding data.

Determination of dexamethasone in plasma of premature neonates using high-performance liquid chromatography

A high-performance liquid chromatographic assay is described for dexamethasone in neonatal plasma. Samples (100 microliters) were extracted with ethyl acetate (1.0 ml) containing 50 ng of beclomethasone. The mobile phase of acetonitrile-0.01 M phosphate buffer (pH 7.0) (45:55, v/v) was pumped at a flow-rate of 1.0 ml/min through an Ultrasphere ODS column (5.0 microns particles). Detection was by UV absorbance at 240 nm. Calibration plots were linear (r2 > 0.999) from 10-1000 ng/ml. Within-day and between-day precision (C.V.%, coefficient of variation) between 15-900 ng/ml was 1.21-20.6%. Inaccuracy was 7.7%, or less. The minimum quantifiable concentration (C.V. approximately 20%) was 15 ng/ml. Recovery (20-1000 ng/ml) exceeded 75%. Concomitant neonatal medication did not interfere.

Fifteen years of operation of a high-performance liquid chromatographic assay for prednisolone, cortisol and prednisone in plasma

A high-performance liquid chromatographic (HPLC) assay first described in 1979 has been modified and revalidated for the simultaneous determination of prednisone, cortisol and prednisolone in human plasma using betamethasone as an internal standard. Revisions include: mobile phase composition; use of a precolumn, automated injector, integrator, and computer software; improved sensitivity and quantitation; thorough investigation of stability, variation, and specimen type; and inclusion of suggested quality control criteria. Plasma-based drug standards are extracted with methylene chloride and washed with sodium hydroxide followed by a water wash. After evaporation of solvent and reconstitution with mobile phase, the extracts are then injected onto a silica gel column (Zorbax SIL) for chromatography with UV absorbance at 254 nm. Calculated limits of quantitation are 10 ng/ml and limits of detection are less than 5 ng/ml. Intra- and inter-day coefficients of variation for quality control samples for all three corticosteroids are less than 11.2%. Recovery and stability data are also provided. Several drugs that may be coadministered do not interfere with the analysis.

General high-performance liquid chromatographic procedures for the rapid screening of natural and synthetic corticosteroids

A study of a multiple high-performance liquid chromatographic procedure for the separation of 30 different corticosteroids is described. Normal- and reversed-phase general methods operating in a wide polarity range have been developed for the rapid screening of multicomponent mixtures. The complementary application of both normal- and reversed-phase methods could permit clarification of uncertainty deriving from analyses performed by only one method.

Effects of indomethacin on the pharmacokinetics and pharmacodynamics of prednisolone in rats

The effect of indomethacin on the disposition of prednisolone and the induction of tyrosine aminotransferase (TAT) was examined in male Sprague-Dawley rats. Rats were pretreated with either indomethacin (5 mg/kg, intraperitoneally) or phosphate buffered saline (control) twice daily for 6 days followed by a single dose of prednisolone. Blood samples were collected after prednisolone administration. In separate animals, hepatic TAT activity (pharmacologic effect) was measured 4 h after the prednisolone dose. In addition, the effect of indomethacin on the in vitro protein binding of prednisolone was examined in pooled rat and human plasma. The clearance and apparent volume of distribution of prednisolone in the control and indomethacin-treated animals were similar, averaging 4.71 versus 4.05 L/h/kg and 1.37 versus 1.33 L/kg, respectively. The elimination half-life was 0.48 h in both groups. Indomethacin also did not affect the protein binding of prednisolone in rat or human plasma. However, indomethacin pretreatment increased the hepatic TAT activity induced by prednisolone. These studies indicate that indomethacin may affect the pharmacological effects of prednisolone without influencing its pharmacokinetics.

Effects of acute and chronic inflammation on the pharmacokinetics of prednisolone in rats

The effects of acute and chronic stages of carrageenan-induced air-pouch inflammation on the pharmacokinetics of prednisolone were studied in male Wistar rats. Chronic inflammation produced a significant increase in the area under the curve (AUC) of prednisolone compared to control animals (6594 +/- 2144 vs 3530 +/- 2164 micrograms.hr/L). The effect of acute inflammation was not significant (AUC = 4996 +/- 3813). Both acute and chronic inflammation also reduced the in vitro plasma protein binding of prednisolone, the reduction being much greater after chronic inflammation. The AUC of free prednisolone after chronic inflammation was 3141 micrograms.hr/L, compared to 1121 micrograms.hr/L in the control group and 1823 micrograms.hr/L after acute inflammation. The mean values of half-life and apparent volume of distribution at steady-state in each group were similar. These results indicate that prednisolone must be used with caution in the treatment of inflammatory diseases because of higher free concentrations of the steroid.

Bioavailability and reversible metabolism of prednisone and prednisolone in man

The pharmacokinetics of prednisone and prednisolone was examined in 12 healthy male subjects to assess the bioavailability and the parameters of reversible metabolism between the two steroids. After an oral prednisone dose of 0.8 mg kg-1 and an intravenous prednisolone dose of 0.66 mg kg-1, the bioavailability was found to be about 62%. The fraction of the dose recovered in the urine as the hydroxylated metabolites of prednisone and prednisolone was lower after the oral prednisone dose, suggesting that poor absorption of prednisone was the main cause of the low bioavailability. There was a high degree of interconversion between prednisone and prednisolone with 76% of the dose being recycled. The formation clearance of prednisolone from prednisone is much greater than the formation clearance of prednisone from prednisolone or the irreversible elimination clearances of the two steroids. The possible dose dependences of bioavailability and interconversion may be important factors in prednisolone therapy.

Prednisolone pharmacodynamics: leukocyte trafficking in the rat

Leukocytes circulate throughout the body patrolling for foreign antigens and facilitating immune responses. Corticosteroids exert their immunosuppressive actions, in part, by inhibiting the normal trafficking of these cells. The rat was used to investigate corticosteroid-induced changes in circulating total lymphocytes, CD4+ cells, and granulocytes. Prednisolone doses of 5, 25, and 50 mg/kg or saline were given i.v. Blood was taken over 24 hr for analysis of cell subsets by flow cytometry. Steroid exposure was assessed by assaying plasma prednisolone by HPLC. Response profiles were complicated, possibly by opposing effects on the recirculation of cells to blood. This prospect was investigated using pharmacodynamic cell trafficking models. Steroid-like effects in saline treated animals that may be due to stress or other factors limited data interpretation. As an animal model to characterize cell trafficking actions, the rat is an imperfect model.

Time course of the changes in prednisolone pharmacokinetics after co-administration or discontinuation of rifampin

We have investigated changes in the pharmacokinetics of prednisolone caused by co-administration or discontinuation of rifampin. Serial IV pharmacokinetic studies of prednisolone (1 mg/kg) in groups of 3 patients over a 1 month period of rifampin co-treatment or after its withdrawal, revealed significant changes in the area under the curve, the total clearance, the non-renal clearance and the half-life. The changes in the pharmacokinetic parameters reached a 1.5 to 2-fold plateau after 2 weeks and the half maximal effect was attained within 5 days. Neither the volume of distribution nor the protein binding of prednisolone were significantly altered.

Determination of cortisol and associated glucocorticoids in serum and urine by an automated liquid chromatographic assay

We describe a method for the determination of urinary free cortisol and glucocorticoids in plasma, used in the diagnosis of adrenal disorders, based on automated reverse-phase high-performance liquid chromatography (HPLC). The within-day and day-to-day CVs were less than 5.5 and 8.0%, respectively. The calibration curves for cortisol and 11-deoxycortisol were linear up to 2000 nmol/L. Cortisol concentrations as low as 3.5 nmol/L in 1 mL of plasma or urine can be measured. Correlation of HPLC results for 40 plasma specimens with those by radioimmunoassay showed r = 0.965. This method is sensitive and free from the interference habitually encountered in immunoassays, and can thus be proposed for research and as a potential reference method.

Evaluation of dose-related pharmacokinetics and pharmacodynamics of prednisolone in man

The pharmacokinetics and pharmacodynamics of prednisolone were evaluated in normal male volunteers. Seven subjects completed 3 phases: 16.4- and 49.2-mg iv prednisolone, and a phase with no drug to assess baseline responses. Plasma concentrations of prednisolone and urine concentrations of prednisolone and 5 metabolites were assayed by HPLC. Protein binding of prednisolone was measured by ultrafiltration. The polyexponential disposition of free and total plasma prednisolone were evaluated and apparent parameters were compared between doses. Suppression of plasma cortisol and alterations in blood basophil and helper-T cell trafficking were used as pharmacodynamic indices. Pharmacodynamic models were used to relate total or free plasma prednisolone concentrations to each of these effects generating response parameters and IC50 (50% inhibitory) concentrations common to both doses. The pharmacokinetics of total drug were comparable to previous findings with CL and Vss increasing with dose. Free prednisolone exhibited slight capacity-limited elimination and distribution as CL and Vss decreased with the larger dose. Pharmacodynamic models jointly fitting all three phases characterized the suppression/trafficking phenomena equally well with use of total or free drug concentrations. In each case the models provided realistic values of parameters relating to steroid sensitivity--in particular IC50--and to the underlying physiology of the affected systems. This study comprehensively elucidates the complexities of prednisolone pharmacokinetics and demonstrates how plasma concentration--time profiles of total or free prednisolone can be utilized for evaluation of prednisolone pharmacodynamics.

Altered prednisolone pharmacokinetics in patients with cystic fibrosis

Prednisolone pharmacokinetics were evaluated in eight patients with cystic fibrosis (CF) (aged 1.8 to 20 years) by assessing absorption of orally administered prednisone (in its active form, prednisolone) and elimination of prednisolone after intravenous administration. After an overnight fast, subjects received intravenously administered doses of prednisolone or orally administered doses of prednisone, 40 mg/1.73 m2 body surface area, before a standardized breakfast. Serial blood samples were collected for 12 hours and analyzed for prednisolone concentration. Prednisolone pharmacokinetics were compared in eight age-matched patients with asthma who required steroids after intravenous administration of prednisolone. The prednisolone pharmacokinetic parameters derived demonstrated an increased total clearance (by 60%), an increased volume of distribution (by 46%), a lower peak concentration (by 35%), and no difference in elimination half-life in patients with CF compared with those with asthma. Bioavailability averaged 88.4% +/- 20.1% of the administered dose. Prednisolone clearance was markedly increased in those with CF. There was a proportional increase in nonrenal clearance, with no difference in renal clearance in those with asthma or CF. The plasma protein binding of prednisolone was only slightly decreased in patients with CF and did not account for the observed pharmacokinetic alteration. The marked increase in prednisolone clearance may necessitate the use of more frequent or higher doses of this steroid in the treatment of patients with CF, leading to a potentially less favorable benefit/risk ratio.

Effect of the anti-inflammatory agent tenidap on the pharmacokinetics and pharmacodynamics of prednisolone

The effect of tenidap, a new nonsteroidal anti-inflammatory agent, on the pharmacokinetics and pharmacodynamics of prednisolone was studied in healthy male subjects. In a randomized crossover study, 12 subjects received either tenidap sodium 120 mg daily or placebo orally for 28 days. On day 21, each subject received a single dose of either 0.8 mg/kg oral prednisone or 0.66 mg/kg intravenous prednisolone followed by the other steroid on day 28. Blood and urine samples were collected, and the pharmacokinetic parameters of prednisone and prednisolone were determined in each treatment period. Pretreatment with tenidap did not cause any significant changes in the overall disposition of prednisone or prednisolone. For example, for free prednisolone, the intravenous area under concentration was 1,144 +/- 195 ng.h/mL and 1,244 +/- 140 ng.h/mL, and the systemic availability after oral prednisone was 53 +/- 10% and 51 +/- 12% with placebo and tenidap, respectively. The renal clearance of prednisolone was significantly reduced after tenidap pretreatment, however (from 143 to 77 mL/min/1.73 m2). The suppression of plasma cortisol and whole blood histamine levels were analyzed to evaluate the potential pharmacodynamic interactions between tenidap and prednisolone. There were no significant changes in the pharmacodynamic parameters between placebo and tenidap groups. The excretion of less than 20% of the dose of prednisolone in urine makes the overall effects of tenidap on prednisolone kinetics and dynamics of inconsequential clinical importance.

Intravenous regional administration of methylprednisolone in rheumatoid arthritis

Intravenous regional administration of corticosteroid (IVRAS) in the treatment of rheumatoid arthritis of the hand has not been reported previously. The method is based on a modification of Bier's block, with substitution of corticosteroid for local anaesthetic. Twenty-two patients were assessed in this double-blind, placebo-controlled study. The technique was safe and effective in improving grip strength, with a group mean improvement of more than 50%. Because suppression of endogenous cortisol production 24 h after treatment was commensurate with the dose of methylprednisolone used (40 mg), we could not exclude that the response may have been due to systemic steroid. Further studies are required to define the real value of IVRAS as it may offer alternative treatment of the joints and tendons within the hand and wrist in some patients rather than more prolonged oral therapy or individual, multiple joint or sheath injections.

Simultaneous determination of beclomethasone, beclomethasone monopropionate and beclomethasone dipropionate in biological fluids using a particle beam interface for combining liquid chromatography with negative-ion chemical ionization mass spectrometry

A new simple and sensitive assay has been developed for the simultaneous quantitative measurement of beclomethasone dipropionate and its hydrolysis products in human plasma and urine. Beclomethasone 17.21-dipropionate, beclomethasone 17-monopropionate, beclomethasone and the internal standard, dexamethasone 21-acetate, were measured by combined liquid chromatography and negative-ion chemical ionization mass spectrometry with methane as the reagent gas. A particle beam interface from Hewlett Packard was used. Under mild operating conditions, abundant and stable characteristic high-mass ions were generated in the ion source of the mass spectrometer by a resonance electron-capture mechanism. The fast extraction procedure requires 1 ml of plasma or urine, and the quantification limit of the method is 1 ng ml-1 for the three tested compounds.