Pharmacodynamics of methylprednisolone phosphate after single intravenous administration to healthy volunteers

Immune regulation by glucocorticoids can be linked to cell type-dependent transcriptional responses

A functional genomics approach uncovers previously undescribed cell type–dependent responses that can be linked to the immunoregulatory actions of glucocorticoids in humans.

Glucocorticoids remain the most widely used immunosuppressive and anti-inflammatory drugs, yet substantial gaps exist in our understanding of glucocorticoid-mediated immunoregulation. To address this, we generated a pathway-level map of the transcriptional effects of glucocorticoids on nine primary human cell types. This analysis revealed that the response to glucocorticoids is highly cell type dependent, in terms of the individual genes and pathways affected, as well as the magnitude and direction of transcriptional regulation. Based on these data and given their importance in autoimmunity, we conducted functional studies with B cells. We found that glucocorticoids impair upstream B cell receptor and Toll-like receptor 7 signaling, reduce transcriptional output from the three immunoglobulin loci, and promote significant up-regulation of the genes encoding the immunomodulatory cytokine IL-10 and the terminal-differentiation factor BLIMP-1. These findings provide new mechanistic understanding of glucocorticoid action and emphasize the multifactorial, cell-specific effects of these drugs, with potential implications for designing more selective immunoregulatory therapies.

Prednisolone is associated with a worse lipid profile than hydrocortisone in patients with adrenal insufficiency

OBJECTIVE

Prednisolone is used as glucocorticoid replacement therapy for adrenal insufficiency (AI). Recent data indicate that its use in AI is associated with low bone mineral density. Data on risk factors for cardiovascular disease in patients with AI treated with prednisolone are scarce, despite this condition being the predominant cause of excess mortality. We aimed to address this question using real-world data from the European Adrenal Insufficiency Registry (EU-AIR).

DESIGN/METHODS

EU-AIR, comprising of 19 centres across Germany, the Netherlands, Sweden and the UK, commenced enrolling patients with AI in August 2012. Patients receiving prednisolone (3-6 mg/day, n = 50) or hydrocortisone (15-30 mg/day, n = 909) were identified and grouped at a ratio of 1:3 (prednisolone:hydrocortisone) by matching for gender, age, duration and type of disease. Data from baseline and follow-up visits were analysed. Data from patients with congenital adrenal hyperplasia were excluded.

RESULTS

Significantly higher mean ± s.d. total (6.3 ± 1.6 vs 5.4 ± 1.1 mmol/L; P = 0.003) and low-density lipoprotein (LDL) cholesterol levels (3.9 ± 1.4 vs 3.2 ± 1.0 mmol/L; P = 0.013) were identified in 47 patients on prednisolone vs 141 receiving hydrocortisone at baseline and at follow-up (P = 0.005 and P = 0.006, respectively). HbA1c, high-density lipoprotein and triglyceride levels, body mass index, systolic and diastolic blood pressure and waist circumference were not significantly different.

CONCLUSIONS

This is the first matched analysis of its kind. Significantly higher LDL levels in patients receiving prednisolone relative to hydrocortisone could predict a higher relative risk of cardiovascular disease in the former group.

Pharmacodynamics and tolerability of repository corticotropin injection in healthy human subjects: A comparison with intravenous methylprednisolone

Repository corticotropin injection (porcine adrenocorticotropic hormone [ACTH] analog) and intravenous methylprednisolone (IVMP) are used to treat inflammatory conditions such as multiple sclerosis (MS) exacerbations and rheumatoid arthritis. This multiple‐dose, randomized, crossover, open‐label study evaluated and compared pharmacodynamic outcomes in subjects who received ACTH analog (80 U subcutaneously) or IVMP (1 g) daily for 5 days. Specific outcome measures included IVMP and cortisol concentrations, total cortisol‐equivalent exposure, immune cell population changes, and tolerability. IVMP and ACTH analog increased granulocyte numbers and decreased lymphocyte counts; effects on both were significantly less pronounced with ACTH analog. Based on total cortisol‐equivalent exposure (assuming linearity), administration of 80 U of ACTH analog equates to 30 mg IVMP. Because IVMP doses significantly higher than 30 mg are usually required to treat MS exacerbations, the lower cortisol‐equivalent exposure of 80 U ACTH analog supports the hypothesis that efficacy of ACTH analog results from both steroid‐dependent and ‐independent properties. Adverse events were mild in severity; subject incidence for adverse‐event reporting was similar following both regimens. The clinical relevance of these findings in autoimmune disease populations is unknown and requires further evaluation.

The effects of glucocorticoids on neuropathic pain: a review with emphasis on intrathecal methylprednisolone acetate delivery

Methylprednisolone acetate (MPA) has a long history of use in the treatment of sciatic pain and other neuropathic pain syndromes. In several of these syndromes, MPA is administered in the epidural space. On a limited basis, MPA has also been injected intrathecally in patients suffering from postherpetic neuralgia and complex regional pain syndrome. The reports on efficacy of intrathecal administration of MPA in neuropathic pain patients are contradictory, and safety is debated. In this review, we broadly consider mechanisms whereby glucocorticoids exert their action on spinal cascades relevant to the pain arising after nerve injury and inflammation. We then focus on the characteristics of the actions of MPA in pharmacokinetics, efficacy, and safety when administered in the intrathecal space.

Bioavailability effect of methylprednisolone by polymeric micelles

PURPOSE

To investigate the effect of PEO-PPO-PEO polymeric micelles (PM) formulation on the bioavailability of methylprednisolone (MP), a treatment of spinal cord injury (SCI), to the blood and spinal cord (SC) of rabbits.

METHODS

The characteristic of MP formulated with PM (MP/PM) was evaluated by critical micelles concentration (CMC), dynamic light scattering (DLS), atomic force microscopy (AFM) and in vitro kinetic release measurements. HPLC was used to analyze the MP disposition in plasma and SC of rabbits receiving single dose intravenous administration. After MP/PM delivery, the mRNA and protein levels of anti-apoptotic marker, Bcl-x(L), were monitored by Reverse Transcription -Real-Time -Polymerase Chain Reaction (RT-qPCR) and Western blotting analysis, respectively.

RESULTS

At a concentration of 0.1% and at 25 degrees C, PEO-PPO-PEO copolymers formed micelles shown by fluorescence probe, DLS and solubility test. The size of the MP/PM was in an average of 60 nm with a single, rounded shape detected under AFM. Being formulated with 6% PM, MP had higher solubility (219.6 +/- 3.6 microg/ml) and release rate (11.1 +/- 0.4 ng min(1/2)) at 37 degrees C. After intravenously administrated with single dose of 1 mg/kg of MP/PM to rabbits, higher levels of MP in plasma and SC were detected compared to animals receiving an equal dose of MP, analyzed by HPLC. PM formulation markedly increased (7-fold) the plasma half-lives (t (1/2)) of MP (from 76.1 +/- 8.0 to 514.3 +/- 70.0 min). In addition, the SC t (1/2) of MP/PM also increased from 278 to 528 min. In SC, the mRNA level of Bcl-x(L) increased 4-fold in animals receiving MP/PM compared to that with MP alone at 7 h post-administration. Similar elevated Bcl-x(L) protein was also detected upon MP/PM administration compared to MP.

CONCLUSIONS

PM vehicle was able to deliver MP to improve its pharmacokinetic profile in plasma and SC with higher expression of anti-apoptotic Bcl-x(L) at both mRNA and protein levels.

Methylprednisolone exposure in pediatric renal transplant patients

Glucocorticoid (GC) dosing is commonly based on body mass or surface area in children, although the drug effects appear to correlate with steroid exposure, rather than dose. We compared the area under the serum concentration-time curve (AUC) of methylprednisolone (MP) with a recombinant cell bioassay measuring serum glucocorticoid bioactivity (GBA), in prediction of side effects in 16 pediatric patients (5.4-18.4 years of age) 2.0-14.9 years after renal transplantation (TX). They received 0.3 mg/kg of MP orally and timed blood samples were drawn up to 8 h postdose. Serum MP concentrations correlated moderately with GBA (r= 0.65, p < 0.0001) with best linear fit at 6 and 8 h (r= 0.72, 0.79, respectively, p < 0.001). MP-AUC(t = 0-8) and GBA(t = 6) were significantly greater in patients who gained excessive weight soon after TX. Change in growth after TX was inversely correlated with MP-AUC (r= 0.73, p < 0.05) and GBA(t = 6) (r= 0.62, p < 0.05). No correlation of MP-AUC or GBA was found with blood glucose or serum lipid concentrations, glomerular filtration rate, bone mineral density or graft histology. In conclusion, GC exposure varies individually and dosing should be adjusted accordingly to control the adverse effects. GBA might provide a complementary tool for monitoring GC exposure but further studies are needed.

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.

Mechanism of glucocorticoid-induced depletion of human CD14+CD16+ monocytes

Healthy donors infused with high doses of glucocorticoids [GCs; methyl-prednisolone (MP); 500 mg/day for 3 days] suffer a selective depletion of the CD14(+)CD16(+) monocytes such that these cells are reduced by 95% on day 5. In vitro studies revealed that at 11 h of culture in the presence of 10(-)(5) M MP, no depletion was observed as yet, but a reduction by 80% was seen after 24 h. In dose-response analysis, MP still led to a 50% reduction of CD14(+)CD16(+) monocytes at 10(-)(7) M. Depletion could not be overcome by addition of the cytokines interleukin-1beta or macrophage-colony stimulating factor, and it was independent of CD95. Depletion was, however, inhibited by the caspase 3,8 blocker z-Val-Ala-Asp, suggesting that cell death occurs in a caspase-dependent manner. Furthermore, blockade of depletion by RU-486 indicates that the intracellular GC receptor (GCR) is involved. Measurement of GCR by flow cytometry revealed a 50% higher level of expression in the CD14(+)CD16(+) monocytes. Our studies show a selective depletion of CD14(+)CD16(+) monocytes by GC treatment in vivo and in vitro, an effect to which the modestly increased level of GCR may contribute.

Pharmacokinetics and pharmacodynamics of methylprednisolone after one bolus dose compared with two dose fractions

OBJECTIVE

Although the elimination half-life of most glucocorticoids is short, they are usually administered once daily, or even on alternate days. Our hypothesis was that this practice might compromise the immunosuppressive effect of those drugs during the second part of the administration interval.

METHODS

Eight healthy male volunteers were randomly assigned to receive intravenous methylprednisolone either 32 mg in the morning, or 16 mg in the morning and 16 mg in the evening in a cross-over design. Methylprednisolone concentrations were determined in plasma by high-pressure liquid chromatography. The total number of CD3+ lymphocytes, and CD4+ and CD8+ T-cell subpopulations was measured in blood. The suppression of these cells was used as a surrogate parameter for the immunosuppressive response, and expressed as reduction of the area under the effect time curve (AUETC). Possible adverse effects on blood pressure, glucose, insulin, and endogenous cortisol levels were monitored.

RESULTS

There were no significant differences in methylprednisolone half-life (2.2 +/- 0.4 h), clearance (575 +/- 113 mL/min), volume of distribution (106 +/- 22 l), concentration producing the half-maximum effect on CD4+ T-cells (1.5 +/- 0.7 ng/mL), and Hill-coefficient (1.2 +/- 0.1), after single or divided dose. However, the total 24 h effect area (AUETC) of lymphocytes, and mainly CD4+ T-cells was significantly more suppressed (P = 0.008) with the divided dosage regimen than after the single dose (8422 +/- 2163 vs. 11,545 +/- 3020 h cells/microL). The surrogate markers for adverse events were not different, except for cortisol.

CONCLUSION

Within a 24-h interval, two dose fractions of methylprednisolone produce a stronger and more sustained immunosuppressive response than one single bolus dose.

High-dose aprotinin modulates the balance between proinflammatory and anti-inflammatory responses during coronary artery bypass graft surgery

OBJECTIVE

To rule out the effect of high-dose aprotinin in respect to the balance of proinflammatory and anti-inflammatory mediators induced by cardiopulmonary bypass (CPB).

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

University-affiliated cardiac center.

PARTICIPANTS

Twenty patients scheduled for coronary artery bypass graft surgery.

INTERVENTIONS

In group A patients (n = 10), high-dose aprotinin was administered (2 x 106 KIU pre-CPB, 2 x 10(6) KIU in prime, 500,000 KIU/hr during CPB). In group C patients (n = 10), placebo was used instead. Proinflammatory interleukin (IL)-6, anti-inflammatory IL-1-receptor antagonist, and clinical parameters were measured 8 times perioperatively. The values are presented as mean +/- SEM.

MEASUREMENTS AND MAIN RESULTS

Four hours after CPB, IL-6 concentration reached the maximum value, being significantly lower in group A patients as compared with group C patients (615 +/- 62 pg/mL v 1,409 +/- 253 pg/mL; p = 0.019). On the first postoperative day, the concentration of IL-6 in group A patients remained lower (219 +/- 24 pg/mL v 526 +/- 123 pg/mL; p = 0.015). In contrast, IL-1-receptor antagonist concentration was higher in group A patients as compared with group C patients after CPB (13,857 +/- 4,264 pg/mL v 5,675 +/- 1,832 pg/mL; p = 0.03). Total postoperative blood loss was lower in group A patients as compared with group C patients (648 +/- 64 mL v 1,284 +/- 183 mL; p = 0.002).

CONCLUSIONS

High-dose aprotinin treatment reduced the inflammatory reaction and postoperative blood loss. The anti-inflammatory reaction was significantly enhanced in these patients, which suggests that the physiologic reaction of the organism to reduce the deleterious effects from CPB is more pronounced by using high-dose aprotinin.

Risks and benefits of preoperative high dose methylprednisolone in surgical patients: a systematic review

BACKGROUND

A single preoperative high dose of methylprednisolone (15 to 30 mg/kg) has been advocated in surgery, because it may inhibit the surgical stress response and thereby improve postoperative outcome and convalescence. However, these potential clinical benefits must be weighed against possible adverse effects.

OBJECTIVE

To conduct a risk-benefit analysis using a meta-analysis, to compare complication rates and clinical advantages associated with the use of high dose methylprednisolone in surgical patients.

METHODS

Randomised controlled trials of high dose methylprednisolone in elective and trauma surgery were systematically searched for in various literature databases. Outcome data on adverse effects, postoperative pain and hospital stay were extracted and statistically pooled in fixed-effects meta-analyses.

RESULTS

We located 51 studies in elective cardiac and noncardiac surgery, as well as traumatology. Pooled data failed to show any significant increase in complication rates. In patients treated with corticosteroids, nonsignificantly more gastrointestinal bleeding and wound complications were observed; the 95% confidence interval boundaries of the numbers-needed-to-harm were 59 and 38, respectively. The only significant finding was a reduction of pulmonary complications (risk difference -3.5%; 95% confidence interval -1.0 to -6.1), mainly in trauma patients.

CONCLUSION

For patients undergoing surgical procedures, a perioperative single-shot administration of high dose methylprednisolone is not associated with a significant increase in the incidence of adverse effects. In patients with multiple fractures, limited evidence suggests promising benefits of glucocorticoids on pulmonary complications.

Corticosteroids during operations using cardiopulmonary bypass

Although corticosteroids have been used for more than 30 years in the context of extracorporeal circulation, there is an ongoing debate about the benefits of their routine application. Methylprednisolone was given as early as 1966 to reduce vasoconstriction during cardiopulmonary bypass (CPB) and to prevent low output syndrome thereafter. An explanation for these findings was recently published. Lipid mediators lead to vasoconstriction and inflammatory cytokine production during CPB. There is no doubt about the potential of corticosteroids to reduce inflammatory and enhance anti-inflammatory mediators, while their possible influence on clinical parameters and their side effects are controversial, as discussed in the literature. There have been contradictory results with respect to pulmonary oxygenation, while an increase in the patient's blood glucose levels, however clinically unimportant, could be demonstrated. The influence of other drugs affecting the inflammatory response has to be taken into account, leading to a patient-specific recommendation for the use of corticosteroids during operations requiring CPB.

Does high-dose methylprednisolone in aprotinin-treated patients attenuate the systemic inflammatory response during coronary artery bypass grafting procedures?

OBJECTIVE

To discover the possible effects of methylprednisolone on the systemic inflammatory response during aprotinin treatment.

DESIGN

Randomized, double-blinded study.

SETTING

University-affiliated heart center.

PARTICIPANTS

Fifty-two patients scheduled for elective coronary artery bypass grafting.

INTERVENTIONS

In the methylprednisolone group (n = 26), 1 g of methylprednisolone was administered 30 minutes before cardiopulmonary bypass (CPB). The 26 control patients received a placebo instead. High-dose aprotinin was administered to all participants.

MEASUREMENTS AND MAIN RESULTS

After CPB, the concentration of the proinflammatory cytokines, interleukin-6 and interleukin-8, was significantly less in the methylprednisolone group. The anti-inflammatory interleukin-10 concentration was, in contrast, greater. After CPB, PaO2 was greater in the methylprednisolone group (245+/-17 v 195+/-16 mmHg). Dynamic pulmonary compliance was also greater, whereas the alveolar-arterial oxygen difference was less (376+/-17 v 428+/-16 mmHg). On arrival in the intensive care unit, the oxygen delivery index was greater in the methylprednisolone group (62+/-2.7 v 54+/-2.3 mL/min/m2) and the oxygen extraction rate was less (25%+/-0.02% v 30%+/-0.02%). After CPB, the cardiac index was significantly greater in the methylprednisolone group (4.1+/-0.2 v 3.6+/-0.2 L/min/m2). These patients had less blood loss postoperatively (616+/-52 v 833+/-71 mL; p = 0.017) and a greater urine output (8,015+/-542 v 6,417+/-423 mL/24 h; p = 0.024).

CONCLUSION

The use of methylprednisolone attenuates the systemic inflammatory response during aprotinin treatment and improves clinical outcome parameters.

Pharmacokinetic/pharmacodynamic aspects of aerosol therapy using glucocorticoids as a model

Glucocorticoids are predominantly prescribed in asthma therapy as aerosols to achieve high pulmonary effects with reduced systemic spill-over and pronounced pulmonary selectivity. A variety of pharmacokinetic parameters are potentially important for determining pulmonary selectivity. The intent of this article, is to provide a practice-relevant theoretical approach to put the importance of these parameters on pulmonary targeting using pharmacokinetic/pharmacodynamic modeling as a tool in perspective. The applied pulmonary pharmacokinetic/pharmacodynamic model revealed that, in addition to recognized parameters such as systemic clearance, oral bioavailability, and efficiency of pulmonary deposition, other factors, such as the pulmonary release (dissolution) rate and dose, are relevant. However, the volume of distribution (for effect parameters not undergoing a diurnal rhythm) and the receptor affinity of a given glucocorticoid are not important for achieving lung targeting.

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.

Pharmacokinetic/pharmacodynamic consequences of space flight

As astronauts prepare for long-term space missions, the question arises of whether drug medication in a zero gravity environment will have the same effects as under normal gravity. There are two potential kinds of changes that must be evaluated: alterations of pharmacokinetics and pharmacodynamics. Pharmacokinetic changes will affect the drug concentrations produced by a certain dosage regimen. They can be caused by changes in: (1) intrinsic clearance (e.g., enzyme activity and renal function), (2) drug binding (e.g., protein binding and tissue binding), (3) blood flow (e.g., liver blood flow and renal blood flow), and (4) bioavailability (e.g., rate and extent of absorption). Pharmacodynamic changes will affect the response that is produced by a given drug concentration. They can be caused by changes in drug-receptor interaction or changes in disease characteristics. Studies of pharmacokinetic and pharmacodynamic changes in microgravity are limited, and predictions of any alterations are mainly extrapolated from known relationships between certain physiologic parameters and their effects on pharmacokinetics in normal gravity. Almost no data is available on changes in pharmacodynamics. Also, no information is available on the relationship between pharmacokinetics and pharmacodynamics. More studies are needed to elucidate the changes in pharmacokinetics and pharmacodynamics in microgravity to ensure the optimum use of drug therapy during space flight.

Comparison of four basic models of indirect pharmacodynamic responses

Four basic models for characterizing indirect pharmacodynamic responses after drug administration have been developed and compared. The models are based on drug effects (inhibition or stimulation) on the factors controlling either the input or the dissipation of drug response. Pharmacokinetic parameters of methylprednisolone were used to generate plasma concentration and response-time profiles using computer simulations. It was found that the responses produced showed a slow onset and a slow return to baseline. The time of maximal response was dependent on the model and dose. In each case, hysteresis plots showed that drug concentrations preceded the response. When the responses were fitted with pharmacodynamic models based on distribution to a hypothetical effect compartment, the resulting parameters were dose-dependent and inferred biological implausibility. Indirect response models must be treated as distinct from conventional pharmacodynamic models which assume direct action of drugs. The assumptions, equations, and data patterns for the four basic indirect response models provide a starting point for evaluation of pharmacologic effects where the site of action precedes or follows the measured response variable.

Receptor-based pharmacokinetic-pharmacodynamic analysis of corticosteroids

The pharmacodynamics of three corticosteroids were investigated after intravenous administration of the phosphate esters of methylprednisolone, dexamethasone, and triamcinolone acetonide to healthy subjects at 20, 50, and 80 mg as well as placebo. Twenty-two different pharmacodynamic parameters were followed as a function of time for 48 hours. Statistically significant effects of the glucocorticoids were an increase in blood glucose levels, a decrease in the number of lymphocytes, eosinophils, basophils, and monocytes, and an increase in the number of granulocytes and stab cells. For the most significant pharmacodynamic effects (lymphocytes, granulocytes, and glucose) a previously derived integrated pharmacokinetic/pharmacodynamic model using plasma concentrations, protein-binding data, and in vitro receptor-binding affinities was used to predict the pharmacodynamic effect-time profiles. Good agreement of predicted and measured effects was observed, confirming the validity of the model. The clinical significance of the model was demonstrated by comparison of model-predicted maintenance doses with empirically determined clinical equivalency doses.

Two-compartment basophil cell trafficking model for methylprednisolone pharmacodynamics

A two-compartment closed model was used to characterize the movement of basophils between blood and extravascular sites resulting from methylprednisolone (MP) exposure. This model is consistent with the view that corticosteroids cause a decrease in the recirculation of these cells from peripheral compartments. Methylprednisolone (Solu-Medrol) was given to healthy males at doses of 10, 25, and 40 mg. Blood samples were collected and assayed for MP by HPLC for pharmacokinetic analysis. Whole blood histamine, an index of circulating basophils, was assessed by RIA over 32 hr. Nonlinear least-squares analysis was carried out to solve for the model parameters reflecting cell movement between compartments and sensitivity (IC50) to the steroid. This model quantitiates the fall and return pattern of biologic response to corticosteroids with a minimal number of parameters which jointly fit several dose/response curves and yields a mean IC50 value of 8.1 ng/ml similar to receptor binding of MP. Properties of the temporal and integrated response curve and model extrapolations over a wide dose range were explored with simulations. Because corticosteroids exert similar effects on other cells in blood, this model may be applicable to various regulatory and immunosuppressive effects.