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

Corticosteroids for the treatment of Duchenne muscular dystrophy: a safety review

INTRODUCTION

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder characterized by progressive muscle degeneration and weakness, caused by mutations in the dystrophin gene. DMD has effects in early age with significantly shortened lifespan and deteriorated quality of life in the second decade, creating an urgent need to develop better therapeutic options. Corticosteroid medication therapy is an integral tool for the management of DMD and several therapeutic options have been recently approved for use.

AREAS COVERED

A comprehensive literature search was completed to examine efficacy and safety profiles of the three corticosteroid medications available for use in DMD patients. The review presents information about the three agents through clinical trials, significant preclinical trials, and comparative studies.

EXPERT OPINION

Managing DMD takes a multidisciplinary approach, although long-term corticosteroid therapy remains a significant therapeutic tool. Based on the available published studies, unequivocal comparison between the benefits of the three medications cannot yet be made. When selecting a medication for a patient, the decision-making process will most likely rely on the minor differences in the adverse effect profiles. Whichever medication is utilized will surely be a part of a larger regimen that includes other novel therapeutic agents.

Perioperative Evaluation and Management of Patients on Glucocorticoids

Myriad questions regarding perioperative management of patients on glucocorticoids (GCs) continue to be debated including which patients are at risk for adrenal insufficiency (AI), what is the correct dose and duration of supplemental GCs, or are they necessary for everyone? These questions remain partly unanswered due to the heterogeneity and low quality of data, studies with small sample sizes, and the limited number of randomized trials. To date, we know that although all routes of GC administration can result in hypothalamic-pituitary-adrenal (HPA) axis suppression, perioperative adrenal crisis is rare. Correlation between biochemical testing for AI and clinical events is lacking. Some of the current perioperative management recommendations based on daily GC dose and duration of therapy may be difficult to follow in clinical practice. The prospective and retrospective studies consistently report that continuing the daily dose of GCs perioperatively is not associated with a higher risk for adrenal crises in patients with GC-induced AI. Considering that oral GC intake may be unreliable in the early postoperative period, providing the daily GC plus a short course of IV hydrocortisone 25 to 100 mg per day based on the degree of surgical stress seems reasonable. In patients who have stopped GC therapy before surgery, careful assessment of the HPA axis is necessary to avoid an adrenal crisis. In conclusion, our literature review indicates that lower doses and shorter duration of supplemental GCs perioperatively are sufficient to maintain homeostasis. We emphasize the need for well-designed randomized studies on this frequently encountered clinical scenario.

Management of Glucocorticoid-Induced Hyperglycemia

Glucocorticoids are potent immunosuppressive and anti-inflammatory drugs used for various systemic and localized conditions. The use of glucocorticoids needs to be weighed against their adverse effect of aggravating hyperglycemia in persons with diabetes mellitus, unmask undiagnosed diabetes mellitus, or precipitate glucocorticoid-induced diabetes mellitus appearance. Hyperglycemia is associated with poor clinical outcomes, including infection, disability after hospital discharge, prolonged hospital stay, and death. Furthermore, clear guidelines for managing glucocorticoid-induced hyperglycemia are lacking. Therefore, this consensus document aims to develop guidance on the management of glucocorticoid-induced hyperglycemia. Twenty expert endocrinologists, in a virtual meeting, discussed the evidence and practical experience of real-life management of glucocorticoid-induced hyperglycemia. The expert group concluded that we should be proactive in terms of diagnosis, management, and post-steroid care. Since every patient has different severity of underlying disease, clinical stratification would help understand patient profiles and determine the treatment course. Patients at home with pre-existing diabetes who are already on oral or injectable therapy can continue the same as long as they are clinically stable and eating adequately. However, depending on the degree of hyperglycemia, modification of doses may be required. Initiating basal bolus with correction regimen is recommended for patients in non-intensive care unit settings. For patients in intensive care unit, variable rate intravenous insulin infusion could be temporarily used, but under supervision of diabetes inpatient team, and patients can be transitioned to subcutaneous insulin once stable baseline assessment and continual evaluation are crucial for day-to-day decisions concerning insulin doses. Glycemic variability should be carefully monitored, and interventions to treat patients should also aim at achieving and maintaining euglycemia. Rational use of glucose-lowering drugs is recommended and treatment regimen should ensure maximum safety for both patient and provider. Glucovigilance is required as the steroids taper during transition, and insulin dosage should be reduced subsequently. Increased clinical and economic burden resulting from corticosteroid-related adverse events highlights the need for effective management. Therefore, these recommendations would help successfully manage GC-induced hyperglycemia and judiciously allocate resources.

Pharmacokinetics and Pharmacodynamics of Repository Corticotropin Injection Compared With Synthetic ACTH1-24 Depot and Methylprednisolone in Healthy Subjects

Repository corticotropin injection (RCI; Acthar Gel) is a naturally sourced complex mixture of adrenocorticotropic hormone (ACTH) analogs and other pituitary peptides. This phase 1, single-center, open-label, randomized parallel study directly compared the pharmacokinetics and pharmacodynamics of RCI and synthetic ACTH_1-24 depot. Methylprednisolone was included to estimate the steroidogenic exposure of RCI and synthetic ACTH_1-24 depot when used to treat nephrotic syndrome. A total of 48 healthy subjects aged 18 to 50 years were randomly assigned 1:1:1 to RCI (80 IU subcutaneously twice weekly on study days 1 and 4), synthetic ACTH_1-24 depot (1 mg subcutaneously twice weekly on study days 1 and 4), or methylprednisolone (32 mg orally once daily on study days 1 through 6). After 2 doses, RCI induced about 5-fold lower free cortisol exposure and an estimated 4-fold lower steroidogenic exposure than synthetic ACTH_1-24 depot. The lower endogenous cortisol response of RCI was achieved despite higher observed mean plasma concentrations of N25-deamidated porcine ACTH_1-39 (the pharmacokinetic marker for RCI) than of ACTH_1-24 . The different pharmacodynamic properties demonstrated by RCI and synthetic ACTH_1-24 depot in this study suggest that these products in the ACTH class are not interchangeable.

Recent advances in prodrug-based nanoparticle therapeutics

Extensive research into prodrug modification of active pharmaceutical ingredients and nanoparticle drug delivery systems has led to unprecedented levels of control over the pharmacological properties of drugs and resulted in the approval of many prodrug or nanoparticle-based therapies. In recent years, the combination of these two strategies into prodrug-based nanoparticle drug delivery systems (PNDDS) has been explored as a way to further advance nanomedicine and identify novel therapies for difficult-to-treat indications. Many of the PNDDS currently in the clinical development pipeline are expected to enter the market in the coming years, making the rapidly evolving field of PNDDS highly relevant to pharmaceutical scientists. This review paper is intended to introduce PNDDS to the novice reader while also updating those working in the field with a comprehensive summary of recent efforts. To that end, first, an overview of FDA-approved prodrugs is provided to familiarize the reader with their advantages over traditional small molecule drugs and to describe the chemistries that can be used to create them. Because this article is part of a themed issue on nanoparticles, only a brief introduction to nanoparticle-based drug delivery systems is provided summarizing their successful application and unfulfilled opportunities. Finally, the review's centerpiece is a detailed discussion of rationally designed PNDDS formulations in development that successfully leverage the strengths of prodrug and nanoparticle approaches to yield highly effective therapeutic options for the treatment of many diseases.

Mechanisms and Clinical Applications of Glucocorticoid Steroids in Muscular Dystrophy

Glucocorticoid steroids are widely used as immunomodulatory agents in acute and chronic conditions. Glucocorticoid steroids such as prednisone and deflazacort are recommended for treating Duchenne Muscular Dystrophy where their use prolongs ambulation and life expectancy. Despite this benefit, glucocorticoid use in Duchenne Muscular Dystrophy is also associated with significant adverse consequences including adrenal suppression, growth impairment, poor bone health and metabolic syndrome. For other forms of muscular dystrophy like the limb girdle dystrophies, glucocorticoids are not typically used. Here we review the experimental evidence supporting multiple mechanisms of glucocorticoid action in dystrophic muscle including their role in dampening inflammation and myofiber injury. We also discuss alternative dosing strategies as well as novel steroid agents that are in development and testing, with the goal to reduce adverse consequences of prolonged glucocorticoid exposure while maximizing beneficial outcomes.

A Review of Deflazacort for Patients With Duchenne Muscular Dystrophy

Objective: The objective of this article is to review the pharmacology, pharmacokinetics, efficacy, safety, dosage and administration, and formulary considerations of deflazacort. Data Sources: A search of MEDLINE and EMBASE (1946 to December 31, 2019) was conducted using the terms deflazacort and Duchenne muscular dystrophy (DMD). Results were limited to clinical trials, humans, and English. Additional sources and data were obtained from the references of included articles and prescribing information. Study Selection and Data Extraction: All articles published after July 2014 related to pharmacology, pharmacokinetics, efficacy, or safety of the therapy in human subjects were included. Data Synthesis: Deflazacort 0.9 mg/kg/d is a once-daily oral corticosteroid and is the first drug of its class to be Food and Drug Administration (FDA) approved for DMD. Studies with deflazacort show improved functional outcomes, delayed onset of cardiomyopathy, reduction in scoliosis surgery, and improved survival, but these improvements are supported by relatively weak evidence. Relevance to Patient Care and Clinical Practice: This review presents data from studies published after the most recent DMD 2016 treatment guidelines and offers prescribing considerations, including pharmacology, pharmacokinetics, adverse effects, formulary considerations, and areas of uncertainty. Conclusions: Deflazacort presents an additional, FDA-approved corticosteroid option for patients that offers improved quality of life for DMD patients. However, there is weak evidence to support these benefits; a full risk-benefit analysis considering adverse events, efficacy, cost, and previous trials of steroid therapy is necessary when selecting therapy. Further research will help clarify deflazacort's optimal dose, duration of treatment, and impact on quality of life.

Comparison of body surface area-based and weight-based dosing format for oral prednisolone administration in small and large-breed dogs

This study compared the pharmacokinetics of Prednisolone (PDS) in small- and large breed dogs with a dosing format based on body surface area (BSA) or body weight (BW). The maximum concentration and area under the curve in large-breed dogs orally administered 2 mg/kg PDS were significantly greater than those in small-breed dogs given 2 mg/kg and in large-breed dogs given 40 mg/m2. The higher blood concentrations that result from BW-based dosing of oral PDS in large-breed dogs can be more than required for effect. Meanwhile, BSA dosing at 40 mg/m may be suboptimal. These findings confirm important differences between standard PDS dosing schemes in dogs while highlighting the need to further optimize PDS dosing in large-breed dogs.

Population Pharmacokinetics of Vamorolone (VBP15) in Healthy Men and Boys With Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an inherited neuromuscular disorder occurring in boys and caused by mutations in the dystrophin gene. Vamorolone is a first-generation delta-9,11 compound that has favorable efficacy and side effect profiles relative to classical glucocorticoids. The pharmacokinetics (PK) of oral vamorolone were assessed in parallel-group studies in healthy men (phase 1, n = 86) and boys with DMD (phase 2a, n = 48) during 14 days of once-daily dosing with a range of doses. Vamorolone exhibited moderate variability in PK, with the maximum plasma concentration usually occurring at 2-4 hours and a half-life of approximately 2 hours for all doses and days examined. Population PK modeling of all data together indicated that the PK of vamorolone can be well described by a 1-compartment model with zero-order absorption. Both men and boys showed a dose-linearity of PK parameters for the doses examined, with no accumulation of the drug during daily dosing. Ingestion with food resulted in markedly enhanced absorption of the drug, as tested in healthy men. There were similar PK of vamorolone in healthy men and DMD boys with apparent clearance averaging 2.0 L/h/kg in men and 1.7 L/h/kg in boys. Overall, vamorolone exhibited well-behaved linear PK, with similar profiles in healthy men and boys with DMD, moderate variability in PK parameters, and absorption and disposition profiles similar to those of classical glucocorticoids.

Head to head comparison of adverse effects and efficacy between high dose deflazacort and high dose prednisolone in systemic lupus erythematosus: a prospective cohort study

BACKGROUND

Deflazacort (DFZ), an oxazoline derivative of prednisolone (PDN), has a dose equivalence of 1.2:1 (mg) to PDN. No study to date has compared adverse effects and efficacy of high doses of DFZ as against high-dose PDN in systemic lupus erythematosus (SLE).

OBJECTIVES

To compare adverse effects of high dose DFZ and PDN in SLE patients, especially in terms of cushingoid features and gain in body weight, 3 and 6 months after initiation of these agents.

METHODS

In both the steroid arms, the following outcome parameters were assessed at 3 and 6 months: (a) cushingoid features by Cushing's Severity Index (CSI) (b) hirsutism by modified Ferriman Gallwey score (c) weight gain by difference (Δ, delta) of weight (in kilograms).

RESULTS

Patients on PDN had 1.6 kg (3.2%) and 2 kg (5.1%) higher median weight gain as compared to those on DFZ at 3 and 6 months respectively ( p = 0.012 and 0.001). PDN caused 10% and 22.2% higher increment in median hirsutism scores as compared to DFZ at 3 months and 6 months follow-up, respectively ( p = 0.004 and 0.002). PDN caused 100% higher increase in median CSI scores than DFZ at 6 months ( p = 0.03). There was no significant difference by generalized estimation equation between the groups with respect to changes in SLEDAI, renal SLEDAI, anti-dsDNA titres and C3/C4 levels. There were two serious infections (requiring hospitalization/intravenous antibiotics) in the PDN group, while none in the DFZ group.

CONCLUSION

Comparable intake and tapering of high dose DFZ and PDN in active SLE revealed 2-fold less weight gain, 2.5-fold less hirsutism and 1.5-fold lower cushingoid severity index as well as lower glycaemic elevation in the DFZ group as compared to PDN group. Both had similar efficacy.

Pharmacokinetics of deflazacort in rabbits after intravenous and oral administration and its interaction with erythromycin

The pharmacokinetic of deflazacort after intravenous and oral administration and the effect of erythromycin on the disposition of deflazacort in rabbits were investigated. A parallel study was carried out in twelve rabbits. The plasma concentration-time profiles of deflazacort were determined after intravenous and oral administration of single dosages of 5 mg/kg in the presence and absence (baseline) of multiple dose erythromycin regimens. Plasma concentrations of 21-desacetyldeflazacort were determined by HPLC. Plasma concentration-time curves were analysed by compartmental pharmacokinetic and noncompartmental methods. The t_½λz values following intravenous and oral administration were 3.67 and 4.96 hr, respectively. The apparent volume of distribution at steady-state (V_ss ) was 4.08 ± 0.31 L/kg, this value indicates that deflazacort is widely distributed into the extravascular tissues. Moreover, bioavailability after oral administration of deflazacort (F = 87.48%) was high. Pharmacokinetic analysis after both routes of administration revealed a significant reduction in total body clearance, a significant increase in mean residence time, half-life and plasma concentrations of the steroid in the presence of multiple dose erythromycin. The results indicated the influence of the erythromycin on deflazacort disposition, which is consistent with a pharmacokinetic-type interaction in the elimination of the drug from the body. Moreover, this interaction should be considered to avoid adverse effects when using both drugs concomitantly.

Epinephrine in anaphylaxis: doubt no more

PURPOSE OF REVIEW

The purpose of this manuscript is to review the literature in support of epinephrine (adrenaline) as first line of therapy of anaphylaxis, not H-1 antihistamines or corticosteroids.

RECENT FINDINGS

The purpose of this review is to assess that epinephrine has a quick onset of activity and rapidly antagonizes multiple mediators that are active in anaphylaxis. Epinephrine has maximal pharmacodynamic effect within 10 min of intramuscular administration into the thigh. As epinephrine has a narrow therapeutic window, prefilled epinephrine auto-injectors are available. There are weight-appropriate doses of epinephrine available with auto-injectors that are prefilled with 0.15, 0.30 and 0.50 mg. In addition, needle lengths vary from 1.17 to 2.50 cm. Different doses and needle lengths are available for paediatric and adult patients, especially obese patients to ensure intramuscular delivery in the thigh.

SUMMARY

Failure to administer epinephrine promptly has resulted in fatalities. Education about anaphylaxis and prompt treatment are critical for patients and their caregivers.

Highly multiplexed and reproducible ion-current-based strategy for large-scale quantitative proteomics and the application to protein expression dynamics induced by methylprednisolone in 60 rats

A proteome-level time-series study of drug effects (i.e., pharmacodynamics) is critical for understanding mechanisms of action and systems pharmacology, but is challenging, because of the requirement of a proteomics method for reliable quantification of many biological samples. Here, we describe a highly reproducible strategy, enabling a global, large-scale investigation of the expression dynamics of corticosteroid-regulated proteins in livers from adrenalectomized rats over 11 time points after drug dosing (0.5–66 h, N = 5/point). The analytical advances include (i) exhaustive tissue extraction with a Polytron/sonication procedure in a detergent cocktail buffer, and a cleanup/digestion procedure providing very consistent protein yields (relative standard deviation (RSD%) of 2.7%–6.4%) and peptide recoveries (4.1–9.0%) across the 60 animals; (ii) an ultrahigh-pressure nano-LC setup with substantially improved temperature stabilization, pump-noise suppression, and programmed interface cleaning, enabling excellent reproducibility for continuous analyses of numerous samples; (iii) separation on a 100-cm-long column (2-μm particles) with high reproducibility for days to enable both in-depth profiling and accurate peptide ion-current match; and (iv) well-controlled ion-current-based quantification. To obtain high-quality quantitative data necessary to describe the 11 time-points protein expression temporal profiles, strict criteria were used to define “quantifiable proteins”. A total of 323 drug-responsive proteins were revealed with confidence, and the time profiles of these proteins provided new insights into the diverse temporal changes of biological cascades associated with hepatic metabolism, response to hormone stimuli, gluconeogenesis, inflammatory responses, and protein translation processes. Most profile changes persisted well after the drug was eliminated. The developed strategy can also be broadly applied in preclinical and clinical research, where the analysis of numerous biological replicates is crucial.

Metabolic considerations of drugs in the treatment of allergic diseases

INTRODUCTION

The clinical management of allergic diseases involves a number of drugs, most of which are extensively metabolized. This review aims to analyze the metabolism and the clinical implications of altered metabolism for these drugs.

AREAS COVERED

The authors present an overview of current knowledge of the metabolism of: antihistamine drugs, glucocorticoids, inhaled β-2 bronchodilators, anticholinergics and other drugs used in allergic diseases, such as cromoglycate, omalizumab, montelukast and epinephrine. Polymorphic drug metabolism is relevant for chlorpheniramine, loratadine and montelukast. Inhibition of drug metabolism is relevant for loratadine, methylprednisolone, fluticasone, mometasone, triamcinolone or prednisolone. Polymorphic pre-systemic metabolism may be relevant to budesonide, fluticasone, beclomethasone, mometasone or salmeterol. The authors also discuss the current information on gene variations according to the 1,000 genomes catalog and other databases. Finally, the authors review the clinical implications of these variations with a particular regard to drugs used in the management of allergic diseases.

EXPERT OPINION

Most drugs used in allergic diseases are extensively metabolized. Drug interaction or adverse reactions related to altered metabolism are relevant issues that should be considered in the management of allergic diseases. However, much additional research is required before defining pharmacogenomic biomarkers for the management of drugs used in allergic diseases.

Determination of deflazacort in human plasma by liquid chromatography-mass spectrometry after liquid-liquid extraction and its application in human pharmacokinetics studies

Purpose:

A sensitive liquid chromatography-mass spectrometric (LC/MS) has been developed and validated for the quantification of deflazacort in human plasma after liquid-liquid extraction (LLE).

Materials and Methods:

Best chromatographic resolution was achieved on a reverse-phase Phenomenex C₁₈ column with the mobile phase of acetonitrile–water (30:70) and isocratic elution resulted in a total run time of about 3.5 min. The analyte was detected by using an electrospray positive ionization mass spectrometry in the selected ion monitoring (SIM) mode. Linearity was obtained in the concentration range studied (5–150 ng/ml) (r = 0.9974).

Results:

Lower limit of quantification (LLOQ) was found to be 5 ng/ml in 500μl plasma sample. Average recovery of the analyte was found to range from 86.80 to 88.19% in plasma at the concentrations of 15.0, 60.0 and 120.0 ng/ml.

Conclusions:

The present method was successfully applied in the pharmacokinetic study of deflazacort in human plasma.

The prediction of human response to ONO-4641, a sphingosine 1-phosphate receptor modulator, from preclinical data based on pharmacokinetic-pharmacodynamic modeling

The pharmacokinetic (PK) and pharmacodynamic (PD) parameters of ONO-4641 in humans were estimated using preclinical data in order to provide essential information to better design future clinical studies. The characterization of PK/PD was measured in terms of decreased lymphocyte counts in blood after administration of ONO-4641, a sphingosine 1-phosphate receptor modulator. Using a two-compartment model, human PK parameters were estimated from preclinical PK data of cynomolgus monkey and in vitro human metabolism data. To estimate human PD parameters, the relationship between lymphocyte counts and plasma concentrations of ONO-4641 in cynomolgus monkeys was determined. The relationship between lymphocyte counts and plasma concentrations of ONO-4641 was described by an indirect-response model. The indirect-response model had an I(max) value of 0.828 and an IC(50) value of 1.29 ng/ml based on the cynomolgus monkey data. These parameters were used to represent human PD parameters for the simulation of lymphocyte counts. Other human PD parameters such as input and output rate constants for lymphocytes were obtained from the literature. Based on these estimated human PK and PD parameters, human lymphocyte counts after administration of ONO-4641 were simulated. In conclusion, the simulation of human lymphocyte counts based on preclinical data led to the acquisition of useful information for designing future clinical studies.

Deflazacort versus other glucocorticoids: a comparison

Steroids form an important component of dermatological therapy and are used since very long time for different conditions in different forms. Though very few molecules are used since very long time, the side effect associated with this group of drugs are almost always there. Recently a new molecule deflazacort has been introduced into Indian market, is a glucocorticoid and a derivative of old molecule prednisolone. Though claimed to be having less side effect, very few studies have been done in Indian prospective. This review will highlight the very basics of this drug and its advantages and disadvantages.

Spectrophotometric and HPLC determination of deflazacort in pharmaceutical dosage forms

Deflazacort (DFZ) is a glucocorticoid used as an anti-inflammatory and immunosuppressant drug. No official methods are available for DFZ determination in pharmaceutical formulations. The objective of this study was to develop, validate and compare spectrophotometric (UV and colorimetric) and high-performance liquid chromatography (HPLC) methods, for the quantitative determination of DFZ in tablets and oral suspension. For the UV method, ethanol was used as the solvent, with detection at 244 nm. The colorimetric method was based on the redox reaction with blue tetrazolium in alkaline medium, with detection at 524 nm. The method by HPLC was carried out using a C18 column, mobile phase consisting of acetonitrile:water (80:20, v/v) with a flow rate of 1.0 mL min-1 and detection at 244 nm. The methods proved linear (r > 0.999), precise (RSD < 5%) and accurate (recovery > 97%). Statistical analysis of the results indicated that the UV and HPLC methods were statistically equivalent, while the values obtained for the colorimetric method differed significantly from the other methods.

Complete remission of non-HIV collapsing glomerulopathy with deflazacort and lisinopril in an adult patient

Collapsing glomerulopathy is a form of focal segmental glomerulosclerosis that is usually associated with HIV-1 infection, and is characterized by its poor prognosis and almost inevitable progression to end-stage renal disease. Its pathological features include collapsed glomeruli, podocyte hypertrophy and hyperplasia, and pseudocrescents. This case report shows the evolution of a 58-year-old patient with non-HIV idiopathic collapsing glomerulopathy who presented with severe nephrotic syndrome and renal insufficiency and was treated with lisinopril and deflazacort, a synthetic corticosteroid that has shown fewer cosmetic effects and glucose and bone metabolism complications than prednisone. The patient responded with full recovery of renal function and normal range of protein excreted in urine after less than two years of treatment. The patient has not suffered a recurrence of his nephrotic syndrome after three years of steroid withdrawal. There is no proven therapy for collapsing glomerulopathy, and this case highlights an alternative for treating this disease with few secondary effects.

Pharmacokinetics and pharmacodynamics of systemically administered glucocorticoids

Glucocorticoids have pleiotropic effects that are used to treat diverse diseases such as asthma, rheumatoid arthritis, systemic lupus erythematosus and acute kidney transplant rejection. The most commonly used systemic glucocorticoids are hydrocortisone, prednisolone, methylprednisolone and dexamethasone. These glucocorticoids have good oral bioavailability and are eliminated mainly by hepatic metabolism and renal excretion of the metabolites. Plasma concentrations follow a biexponential pattern. Two-compartment models are used after intravenous administration, but one-compartment models are sufficient after oral administration.The effects of glucocorticoids are mediated by genomic and possibly nongenomic mechanisms. Genomic mechanisms include activation of the cytosolic glucocorticoid receptor that leads to activation or repression of protein synthesis, including cytokines, chemokines, inflammatory enzymes and adhesion molecules. Thus, inflammation and immune response mechanisms may be modified. Nongenomic mechanisms might play an additional role in glucocorticoid pulse therapy. Clinical efficacy depends on glucocorticoid pharmacokinetics and pharmacodynamics. Pharmacokinetic parameters such as the elimination half-life, and pharmacodynamic parameters such as the concentration producing the half-maximal effect, determine the duration and intensity of glucocorticoid effects. The special contribution of either of these can be distinguished with pharmacokinetic/pharmacodynamic analysis. We performed simulations with a pharmacokinetic/pharmacodynamic model using T helper cell counts and endogenous cortisol as biomarkers for the effects of methylprednisolone. These simulations suggest that the clinical efficacy of low-dose glucocorticoid regimens might be increased with twice-daily glucocorticoid administration.

On the Prediction of the Human Response: A Recycled Mechanistic Pharmacokinetic/Pharmacodynamic Approach

Although it is routine to predict the blood or plasma pharmacokinetics of compounds for man based upon preclinical studies, the real value of such predictions only comes when linked to drug effects. In the first example, the immunomodulator, FTY720, the first sphingosine-1-phosphate receptor agonist, stimulates the sequestration of lymphocytes into lymph nodes thus removing cells from blood circulation. A prior physiology-based pharmacokinetic model fitted the concentration-time course of FTY720 in rats. This was connected to an indirect response model of the lymphocyte system to characterise the cell trafficking effects. The IC(50) of FTY720 was different in the rat compared with the monkey; man was assumed to be similar to the monkey. The systemic lymphocyte half-lives were also different between species. To make predictions of the pharmacodynamic behaviour for man, two elements are required, i) systemic exposure, in this case from an upscaled physiology based model, and ii) an estimate of lymphocyte turnover in man, gained from the literature from other drug treatments. Predictions compared well with clinical results. The second example is the monoclonal antibody Xolair, designed to bind immunoglobulin E for atopic diseases. A mechanism based two-site binding model described the kinetics of both Xolair and endogenous IgE. This model has been reused for other monoclonal antibodies designed to bind fluid-phase ligands. Sensitivity analysis shows that if differences across species in the kinetics of the endogenous system are not accounted for, then pharmacokinetic/pharmacodynamic models may give misleading predictions of the time course and extent of the response.

Lack of gender effect on the pharmacokinetics and pharmacodynamics of dexamethasone in the camel after intravenous administration

The pharmacokinetics and pharmacodynamics of dexamethasone were studied in six male and six female camels after a single intravenous dose (0.05 mgkg(-1) body weight) of dexamethasone. The pharmacokinetic parameters of the two-compartment pharmacokinetic model for female and male camels, respectively (mean+/-SEM) were as follows: terminal elimination half-lives were 8.02+/-1.15 and 7.33+/-0.80 h, total body clearances were 95.5+/-16.0 and 124.5+/-11.9 ml h(-1) per kg, volumes of distribution at steady state were 0.72+/-0.08 and 0.87+/-0.14 litre kg(-1), and the volumes of the central compartment were 0.12+/-0.02 and 0.17+/-0.02 litre kg(-1). There was no significant difference in any pharmacokinetic parameter between female and male camels. Pharmacodynamic effects were evaluated by measuring endogenous plasma cortisol, circulating lymphocytes and neutrophils numbers and were analysed using indirect pharmacokinetic/pharmacodynamic models. The estimated IC50 of dexamethasone for cortisol and lymphocytes for female and male camels were 3.74+/-0.99 and 2.28+/-1.09 and 2.63+/-0.71 and 2.41+/-0.79 ng ml(-1), respectively. The EC50 for neutrophils for female and male camels were 24.5+/-5.83 and 20.2+/-3.82 ng ml(-1), respectively. There was no significant difference in any pharmacodynamic parameter between female and male camels. Dexamethasone in urine could be detected for 4-5 days by enzyme-linked immunosorbent assay and for 3-4 days by liquid chromatography/mass spectrometry after an intravenous dose of 0.05 mg kg(-1) body weight.

Drug targeting by long-circulating liposomal glucocorticosteroids increases therapeutic efficacy in a model of multiple sclerosis

High-dose glucocorticosteroid hormones are a mainstay in the treatment of relapses in multiple sclerosis. We searched for a way to deliver ultra high doses of glucocorticosteroids to the CNS of rats with experimental autoimmune encephalomyelitis (EAE) using a novel formulation of polyethylene glycol (PEG)-coated long-circulating liposomes encapsulating prednisolone (predni solone liposomes, PL). 3H-labelled PL showed selective targeting to the inflamed CNS, where up to 4.5-fold higher radioactivity was achieved than in healthy control animals. HPLC revealed much higher and more persistent levels of prednisolone in spinal cord after PL compared with an equal dose of free prednisolone. Gold-labelled liposomes could be detected in the target tissue, mostly taken up by macrophages (Mphi), microglial cells and astrocytes. Blood-brain barrier disruption was greatly reduced by 10 mg/kg PL, which was superior to a 5-fold higher dose of free methylprednisolone (MP). PL was also superior to MP in diminishing T-cell infiltration by induction of T-cell apoptosis in spinal cord. Mphi infiltration was clearly decreased only by PL. The percentage of tumour necrosis factor-alpha (TNF-alpha)-positive T cells or Mphi was greatly reduced by PL and by MP. No adverse effects on glial cells were detected. A single injection of PL clearly ameliorated the course of adoptive transfer EAE and EAE induced by immunization. In conclusion, PL is a highly effective drug in treatment of EAE, and is superior to a 5-fold higher dose of free MP, possibly by means of drug targeting. These findings may have implications for future therapy of autoimmune disorders such as multiple sclerosis.

Population pharmacokinetics and pharmacodynamics of ciclesonide

Ciclesonide is a novel glucocorticoid that is converted into ciclesonide--active principle (CIC-AP) in the lung. The study objectives were to identify a structural model for population pharmacokinetic (PK) analysis of CIC-AP using nonlinear mixed-effects modeling, assess the influence of select covariates on PK and/or pharmacodynamic (PD) parameters, and investigate the effects of CIC-AP on endogenous cortisol. Pooled concentration data from nine phase I studies (dose: 400-3600 micrograms) involving healthy and asthmatic patients were included in the PK analysis. There were 151 subjects (3300 observations) for the CIC-AP population PK analysis. Various models examined inter- and intrasubject variability for the PK parameters. Population estimates of the PK parameters of clearance and volume of distribution were 396 L/h (64.8% co-efficient of variation [CV]) and 1190 L (41.2% CV), respectively. Pharmacodynamic population estimates included maximum cortisol release rate, 3140 ng/h (5.4% CV). The EC50 of CIC-AP was 0.88 ng/mL. Ciclesonide is a safe corticosteroid that causes negligible cortisol suppression. The disposition and effect of CIC-AP can be described using mixed-effect modeling. The estimated EC50 is similar to mean Cmax from an 800-micrograms dose, further suggesting CIC-AP has little effect on cortisol suppression.

Pharmacokinetics and pharmacodynamics of dexamethasone sodium-m-sulfobenzoate (DS) after intravenous and intramuscular administration: a comparison with dexamethasone phosphate (DP)

The pharmacokinetics (PK) and pharmacodynamics (effects on blood lymphocytes) of dexamethasone (D) after intravenous (i.v.) administration of dexamethasone phosphate (DP, 10 mg, equivalent to 8.3 mg of dexamethasone) and after intravenous and intramuscular (i.m.) administration of dexamethasone sulfobenzoate sodium (DS, 9.15 mg, equivalent to 6 mg of dexamethasone) were assessed. Only 25% of DS was converted into dexamethasone with a half-life for DS of 5.4 hours and 7.4 hours after i.v. and i.m. administration, respectively. Consequently, the mean residence time of D after both i.m. and i.v. administration of DS (10.4-11.6 h) was longer than that after DP administration (6.1 h). The smaller lymphocyte suppression induced by DS (50% of that after DP administration) was shown to be related to differences in the pharmacokinetics. This study revealed significant differences in the pharmacokinetics of D after administration of DS and DP and stresses the importance of the prodrug for the pharmacological response. Because of the slow and incomplete conversion of DS into dexamethasone, its use in emergency medicine situations should be critically evaluated.

The effects of the glucocorticoids prednisolone, deflazacort and beclomethasone-dipropionate on the RM 3/1 macrophage in human peripheral blood

Different glucocorticoids (GC) applied intravenously, subcutaneously or in vitro exert only small differences in the ability to raise RM 3/1 macrophages from human blood monocytes. Dermal application however reveals a dose-dependent difference between GC. The present experiments were designed to study the efficacy of oral and topical application in this model. We also intended to obtain some information about the qualitative differences between the effects of prednisolone and deflazacort, which was reported to cause less adverse reactions than other GC. Both GC were orally administered to probands in doses regarded as equivalent with respect to general GC effects by the manufacturers of deflazacort (5-6 mg or multiples). A single dose of 5 mg prednisolone had no effect; 50 mg increased the number of RM 3/1 macrophages within 12 h from a basal level of 8.5% to about 80% similar to an intravenous or subcutaneous administration of GC. 10 mg prednisolone enhanced the number of RM 3/1 macrophages also within 12 h, reaching a mean maximum of about 60% at 24 h, declining thereafter. 12 mg deflazacort raised the number of RM 3/1 macrophages much slower, reaching a maximum of 30% (average) after 48 h. The interindividual variation was found to be mainly the time lag between dosage and maximum effect. Interindividual differences of prednisolone effects concerned mainly the maximal increase of RM 3/1 macrophages after 24 h. These results show that in this test system deflazacort was found to be less effective than expected. To elucidate the topical influence of GC, probands inhaled twice daily 0.5 mg beclomethasone-dipropionate over a period of 11 days. No effect on the number of RM 3/1 macrophages was observed, suggesting that beclomethasone applied in this dose did not cause systemic GC reactions.

Determination of 21-hydroxydeflazacort in human plasma by high-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry. Application to bioequivalence study

A liquid chromatographic atmospheric pressure chemical ionization tandem mass spectrometric method is described for the determination of 21-hydroxydeflazacort in human plasma using dexamethasone 21-acetate as an internal standard. The procedure requires a single diethyl ether extraction. After evaporation of the solvent under a nitrogen flow, the analytes are reconstituted in the mobile phase, chromatographed on a C18 reversed-phase column and analyzed by mass spectrometry via a heated nebulizer interface where they are detected by multiple reaction monitoring. The method has a chromatographic run time of less than 5 min and a linear calibration curve with a range of 1-400 ng ml(-1) (r>0.999). The between-run precision, based on the relative standard deviation for replicate quality controls, was < or =5.5% (10 ng ml(-1)), 1.0% (50 ng ml(-1)) and 2.7% (200 ng ml(-1)). The between-run accuracy was +/-7.1, 3.8 and 4.8% for the above concentrations, respectively. This method was employed in a bioequivalence study of two DFZ tablet formulations (Denacen from Marjan Industria e Comercio, Brazil, as a test formulation, and Calcort from Merrell Lepetit, Brazil, as a reference formulation) in 24 healthy volunteers of both sexes who received a single 30 mg dose of each formulation. The study was conducted using an open, randomized, two-period crossover design with a 7-day washout interval. The 90% confidence interval (CI) of the individual geometric mean ratio for Denacen/Calcort was 89.8-109.5% for area under the curve AUC(0-24 h) and 80.7-98.5% for Cmax. Since both the 90% CI for AUC(0-24 h) and Cmax were included in the 80-125% interval proposed by the US Food and Drug Administration, Denacen was considered bioequivalent to Calcort according to both the rate and extent of absorption.

A pharmacokinetic/pharmacodynamic approach to predict the cumulative cortisol suppression of inhaled corticosteroids

The suppression of endogenous cortisol release is one of the major systemic side effects of inhaled corticosteroids in the treatment of asthma. The circadian rhythm of the endogenous cortisol release and the resulting plasma concentrations as well as the release suppression during corticosteroid therapy could previously be described with an integrated PK/PD model. Based on this model, a PK/PD approach was developed to quantify and predict the cumulative cortisol suppression (CCS) as a surrogate marker for the systemic activity of inhaled corticosteroid therapy. The presented method was applied to predict CCS after single doses and during short-term multiple dosing of the inhaled corticosteroids flunisolide (FLU), fluticasone propionate (FP), and triamcinolone acetonide (TCA), and after oral methylprednisolone as systemic reference therapy. Drug-specific PK and PD parameters were obtained from previous single-dose studies and extrapolated to the multiple-dose situation. For single dosing, a similar CCS within the range of 16-21% was predicted for FP 250 micrograms, FLU 500 micrograms, and TCA 1000 micrograms. For multiple dosing, a respective CCS of 28-33% was calculated for FLU 500 micrograms bid, FP 250 micrograms, bid, and TCA 1000 micrograms bid. Higher cortisol suppression compared to these single and multiple dosing regimens of the inhaled corticosteroids was predicted after oral doses of only 1 mg and 2 mg methylprednisolone, respectively. The predictive power of the approach was evaluated by comparing the PK/PD-based simulations with data reported previously in clinical studies. The predicted CCS values were in good correlation with the clinically observed results. Hence, the presented PK/PD approach allows valid predictions of CCS for single and short-term multiple dosing of inhaled corticosteroids and facilitates comparisons between different dosing regimens and steroids.

Involvement of intestinal P-glycoprotein in the restricted absorption of methylprednisolone from rat small intestine

The interaction between steroid hormones and intestinal P-glycoprotein was investigated by measuring intestinal absorption from rat small intestine in situ. Prednisolone and hydrocortisone were rapidly absorbed from the entire small intestine. In contrast, methylprednisolone absorption was significantly retarded in jejunum and ileum by an intestinal efflux system. In the presence of verapamil an quinidine, the retarded absorption of methylprednisolone was completely recovered, suggesting that P-glycoprotein is responsible for the unique features of methylprednisolone absorption. A requisite for the substrate of intestinal P-glycoprotein seemed to be 6 alpha-methyl group in the steroid structure. Substrate specificity of intestinal P-glycoprotein to steroid hormones was shown to be in part different from those in other tissues such as adrenal gland. Little of all three steroid hormones disappeared in the supernatant of mucosal homogenate from rat small intestine, indicating that intestinal metabolism of these steroid hormones was relatively small.

Pharmacokinetic/pharmacodynamic evaluation of systemic effects of flunisolide after inhalation

The pharmacokinetics and pharmacodynamics of flunisolide were studied in healthy volunteers after inhalation. In the morning on the day the study began, volunteers inhaled 0.5 mg of flunisolide with and without oral administration of charcoal, or 1 mg, 2 mg, and 3 mg of flunisolide with concomitant administration of charcoal. A placebo group was used to assess the endogenous cortisol, granulocyte, and lymphocyte baseline levels. Flunisolide plasma levels were determined by high-performance liquid chromatography using a tandem mass spectrometer as detector (HPLC/MS/MS). Cortisol plasma levels and differential white blood cell counts were obtained over 12 hours. An integrated pharmacokinetic/pharmacodynamic (PK/PD) model was applied to link the flunisolide plasma concentrations with the effects on lymphocytes, granulocytes, and cortisol. Maximum concentration levels of 3 to 9 ng/mL of flunisolide were observed after 0.2 to 0.3 hours for all of the investigated doses. The terminal half-life ranged from 1.3 to 1.7 hours. There was no statistical difference between treatments in the presence or absence of orally administered charcoal. The pharmacokinetic/pharmacodynamic (PK/PD) models satisfactorily described the time-courses of the effects on granulocytes, lymphocytes, and cortisol suppression. The resulting E50-values (concentrations to induce 50% of the maximum effect) concurred with the reported values of in vitro receptor binding affinities. The duration of the systemic effects were short because of the short half-life of the drug. Cumulative cortisol suppression increased with dose administration and ranged from 20% to 36%. The PK/PD simulations resulted in a smaller degree of cortisol suppression for the drug administered at 10 PM. The cumulative change from baseline was slightly smaller for the effects on granulocytes and lymphocytes than those on cortisol. This information promotes the comparison with other inhaled glucocorticoids.

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.

Bilateral tibial marrow ablation in rats induces a rapid hypercalcemia arising from extratibial bone resorption inhibitable by methylprednisolone or deflazacort

The goals of this study were to quantitate biochemical markers of bone metabolism on days 1-15 after bilateral tibial marrow ablation surgery in young adult rats and to determine the effect of a single dose of methylprednisolone (2 mg/kg) or deflazacort (2.5 mg/kg) given at the time of ablation. Unexpectedly, serum calcium levels rose to a maximum of 15.9 mg/dl on day 7 after marrow ablation and remained above normal through day 15. This increase was blocked by a single intramedullary injection of methylprednisolone or deflazacort immediately following ablation; however, the fact that both drugs produced a characteristic rapid 3- to 10-fold increase in the serum alpha 2-macroglobulin level demonstrates that the drugs rapidly reached the circulation. Both methylprednisolone and deflazacort also inhibited intramedullary deposition of collagen by 40-60% on day 7, a time near which operated control animals achieved maximal accumulation of new bone in this model. Histological comparisons among the three experimental groups were largely consistent with biochemical results. The urinary hydroxyproline/creatine ratio for the operated control group doubled on day 3 and then returned to presurgical levels on day 7 and later. The timing and size of the hydroxyproline/creatinine peak, as well as the fact that the intratibial osteoclastic response peaks on days 8-10 after ablation, suggests it results from extratibial bone resorption induced by marrow ablation. Consistent with this rationale, urinary calcium excretion in operated controls rose 9-fold from day 0 to day 3 and appeared to plateau over the period from day 3 to day 9, before returning to a near presurgical level on day 15. Elevated excretion of calcium noted on days 9-15 in deflazacort-treated animals, which occurs in the absence of a detectable increase in resorption marker hydroxyproline, may however be due to the known action of glucocorticoids in increasing kidney filtration of calcium. In summary, this is the first report to show that bilateral tibial marrow ablation in rats causes a rapid hypercalcemia and calciuria which is accompanied initially by a peak of bone resorption marker urinary hydroxyproline. We speculate that the source of calcium and hydroxyproline is extratibial osteoclastic bone resorption induced by circulating cytokines whose release from ablated tibias or osteoclastogenic action is inhibitable by methylprednisolone and deflazacort.

Pharmacokinetic and pharmacodynamic evaluation of triamcinolone acetonide after intravenous, oral, and inhaled administration

Triamcinolone acetonide (TCA) is a corticosteroid that is frequently used in the treatment of asthma. After inhalation, TCA can become systemically available when the inhaled formulation is swallowed, causing undesirable systemic effects. A clinical study was conducted to determine the systemic side effects of TCA after intravenous (2 mg as phosphate ester), oral (5 mg), and inhaled (2 mg) administration. Blood samples were collected at appropriate times over 24 hours, and TCA concentrations in plasma were measured by high-performance liquid chromatography and radioimmunoassay. Free drug concentrations were determined by ultrafiltration for correlating pharmacokinetics and pharmacodynamics. The free fraction of TCA (+/- standard deviation) was 29.0 +/- 1.3% and was independent of the investigated concentration range up to 1,000 ng/mL. Pharmacodynamic parameters were determined by monitoring lymphocytes, granulocytes, and cortisol. Pharmacokinetic/pharmacodynamic modeling was performed using a modified Emax model for lymphocytes and granulocytes. A novel linear release rate model was used to characterize the cortisol data. The E50 values determined from all three pharmacodynamic endpoints were not significantly different for the three treatments, indicating that these effects can be explained based on systemic steroid concentrations.