Dexamethasone Clearance Research Articles

THU213 Posterior Reversible Encephalopathy Syndrome As A Rare Presentation Of ACTH-dependent Cushing Syndrome In A Pediatric Patient

Abstract Disclosure: E.E. Bell-Sambataro: None. C. Tatsi: None. P. Chittiboina: None. S.A. Bowden: None. Background: Cushing disease (CD), caused by ACTH-secreting pituitary adenoma, is the most common cause of Cushing Syndrome (CS) in children > 5 years of age. Hypertension is reported in up to 50% of pediatric cases with CS. We report a challenging pediatric case with a rare presentation of hypertensive emergency associated with CD. Clinical Case: A 6-year-old female with 3 month-history of rapid weight gain (8 kg), round face, and hypertrichosis presented to emergency department for abdominal pain from nephrolithiasis and was noted to have severe hypertension. While in ED, she developed status epilepticus and altered mental status. Brain MRI findings were consistent with posterior reversible encephalopathy syndrome (PRES). Her hypertensive encephalopathy gradually improved with aggressive anti-hypertensive and anti-epileptic therapy. Further studies confirmed hypercortisolism with markedly elevated urine free cortisol of 1288 ug/day (<18 ug/day) and lack of diurnal variation of serum cortisol (8 AM cortisol of 47.9 ug/dL, midnight cortisol of 20.3 ug/dL). ACTH level of 23 pg/mL suggested ACTH-dependent CS. Low dose (1 mg) dexamethasone suppression test (DST) failed to suppress 8 am cortisol (31.4 ug/dL). High dose DST (120 mcg/kg) suppressed serum cortisol to 67%- borderline threshold for CD, likely due to increased dexamethasone clearance by anticonvulsant. Pituitary MRI did not reveal a visible lesion. Desmopressin stimulation test showed stimulation of ACTH by 700% and cortisol by 160% suggesting pituitary source. Inferior petrosal sinus sampling showed a mildly increased gradient in central to peripheral plasma ACTH of 1.7 at baseline (>2) and post-stimulation of 2.5 (>3). ACTH gradient did not reach cutoffs for pituitary source, likely due to insufficient catheterization of petrosal sinus from anatomically small blood vessels. Given her severity, she underwent surgical pituitary exploration. Postoperative morning cortisol was <5 mcg/dL, with decreased midnight salivary cortisol level obtained 2 months after surgery. She developed post-operative central hypothyroidism but did not have diabetes insipidus. She had a 4 kg weight loss with increased height percentile 5 months after surgery and remains under close monitoring. Conclusion: PRES is a clinical-radiographic disorder characterized by seizures, encephalopathy with neuroimaging findings of reversible cortical and subcortical vasogenic edema. Hypertension induced by marked hypercortisolism precipitated by pain is likely the etiologic factor. Prompt recognition and treatment of PRES are crucial to prevent further life-threatening complications and permanent neurological damage. Early diagnosis and treatment of CD are critical to prevent associated morbidities. Pituitary exploration by expert neurosurgery team should be considered in patients with MRI-negative CD. Presentation: Thursday, June 15, 2023

Population pharmacokinetics of dexamethasone in critically ill COVID-19 patients: Does inflammation play a role?

PurposeThe aim of this study is to design a population pharmacokinetic study to gain a deeper understanding of the pharmacokinetics of dexamethasone in critically ill COVID-19 patients in order to identify relevant covariates that can be used to personalize dosing regimens. MethodsBlood samples from critically ill patients receiving fixed-dose intravenous dexamethasone (6 mg/day) for the treatment of COVID-19 were sampled in a retrospective pilot study. The data were analyzed using Nonlinear Mixed Effects Modeling (NONMEM) software for population pharmacokinetic analysis and clinically relevant covariates were selected and evaluated. ResultsA total of 51 dexamethasone samples from 18 patients were analyzed and a two-compartment model fit the data best. The mean population estimates were 2.85 L/h (inter-individual-variability 62.9%) for clearance, 15.4 L for the central volume of distribution, 12.3 L for the peripheral volume of distribution and 2.1 L/h for the inter-compartmental distribution clearance. The covariate analysis showed a significant negative correlation between dexamethasone clearance and CRP. ConclusionsDexamethasone PK parameters in ICU COVID patients were substantially different from those from non-ICU non-COVID patients, and inflammation may play an important role in dexamethasone exposure. This finding suggests that fixed-dose dexamethasone over several days may not be appropriate for ICU COVID patients.

PMON98 High-dose dexamethasone suppression test in ACTH-dependent Cushing's syndrome: Lessons learned on the lack of cortisol suppression

Abstract Background The overnight 8-mg high-dose dexamethasone suppression test (HDDST) has been used to discern Cushing's disease from ectopic ACTH production. However, because of its reported low diagnostic accuracy, its use is limited to the assessment of ACTH-dependent Cushing's disease when combined with a corticotropin releasing hormone (CRH) or a desmopressin stimulation test. We evaluated a patient with Cushing's disease in whom the HDDST failed to identify the pituitary source. We point to limitations in test interpretation and highlight the need of future studies to enhance understanding of the clinical utility of this non-invasive test. Clinical Case A 42-year-old male presented with lower extremity cellulitis and hypertensive emergency. He reported increased abdominal girth, easy bruising, severe back pain and proximal muscle weakness and noted headache and blurred vision. Exam was pertinent for obesity (body mass index 31.5 kg/m2), moon facies, dorso-cervical hump and prominent abdominal striae. Lumbar and thoracic compression fractures were noted on imaging. The elevated 24-hour urinary free cortisol level (198 ug/dL; reference: 10-100 ug/24hr) and lack of suppression on the overnight 1-mg dexamethasone suppression test (morning cortisol 23.7 ug/dL) confirmed Cushing's syndrome; a high ACTH level of 92 pg/dL defined it as ACTH-dependent. The 8-mg HDDST resulted in only a 9.7% reduction of his baseline morning cortisol. The patient was not on any medications that enhanced dexamethasone clearance. Serum dexamethasone levels were measured to aid in test interpretation and, although a level was provided, reference values for the single overnight 8-mg dose of dexamethasone were lacking. A CRH stimulation test was performed and resulted in a 60% increase in ACTH levels from baseline, supporting the diagnosis of Cushing's disease. Additionally, a pituitary MRI revealed a suprasellar 2.5×1.5×1.3 cm mass. Due to ambiguity posed by the HDDST result, despite tumor size, neurosurgery requested inferior petrosal sinus sampling (IPSS). Prior to this procedure, the patient underwent an overnight 16-mg HDDST. While limited information remains on the diagnostic performance of this test, we observed that the baseline morning cortisol decreased by 53.9%. IPSS confirmed the diagnosis of Cushing's disease and pathology identified a corticotroph adenoma. Conclusion The diagnosis of Cushing's disease is complex and recommendations continue to evolve. Th role of the HDDST in combination with another dynamic test remains clinically relevant. It is important that when considering a HDDST, clinicians review medication history to exclude agents that may interfere with dexamethasone metabolism. Our case highlights the need of studies that determine an appropriate reference range for dexamethasone plasma levels after a single 8-mg overnight dose and that evaluate the diagnostic performance of the HDDST in this context. It also brings attention to the need of further elucidating the diagnostic utility of a higher dexamethasone dose in the evaluation of ACTH-dependent Cushing's syndrome. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

ODP302 Cushing's Disease: A Challenging Diagnosis in Patients with Underlying Co-Morbidities

Abstract Introduction Cushing's disease (CD) is a rare endocrine disorder with significant morbidity and mortality. This case is a complicated ACTH (adrenocorticotropic hormone)-dependent hypercortisolism with a negative pituitary MRI inthe setting of underlying liver cirrhosis and chronic kidney disease. Hypercortisolism work up was challenging due to liver and kidney disease. Case Presentation A 42-year-old woman with a history of liver cirrhosis(MELDscore: 19) and stage 3b chronic kidney disease (CKD) presented with nausea, vomiting and abdominal pain. She reported proximal muscle weakness. On examination, she had central adiposity with large purple abdominal striae and proximal muscle wasting. Medical history was pertinent for uncontrolled hypertension and type 2 diabetes mellitus. Due to concern for Cushing's syndrome, an overnight 1 mg dexamethasone suppression test (DST) was performed. She had an inappropriately elevated morning cortisol of 10.1 mcg/dL (n < 1.8 mcg/dL), but suboptimal dexamethasone level of 104 ng/dL (140-295 ng/dL), suggesting incomplete absorption secondary to emesis. A repeat DST was not performed given concerns for reduced dexamethasone clearance with her underlying renal and liver disease. Her 24-hour urine free cortisol (UFC) was elevated at 55 ug/24 hr (6-42 ug/24 hr). A repeat 24-hour UFC was again elevated at 265 ug/24 hr (6-42 ug/24 hr). Three late night salivary cortisol levels were also elevated at 0.231 ug/dL, 0.429 ug/dL and 0.19 ug/dL (n <0. 01-0. 09 ug/dL). Diagnosis of Cushing's syndrome was confirmed. ACTH level obtained was detectable at 70.1 pg/mL (7.2-63.3 pg/mL), suggestive of ACTH-dependent Cushing's syndrome. Pituitary MRI without contrast was obtained due to CKD. MRI reported no pituitary abnormalities. High dose DST was not performed due to concerns for aforementioned reduced dexamethasone clearance and due to lack of availability of CRH (corticotropin-releasing hormone), CRH stimulation testing was not done. She underwent inferior petrosal sinus sampling (IPSS) which showed central to peripheral ACTH ratio of 2.11 at baseline and ratios of 3.53, 3.45 and 3.32 at 5 minutes, 10 minutes and 15 minutes respectively after vasopressin stimulation, solidifying the diagnosis of Cushing's disease. Patient is now scheduled for an exploration of the sella via endoscopic endonasal approach. Conclusion This case highlights the limitations of biochemical tests and imaging modalities in the workup of hypercortisolism, notably in patients with underlying liver and kidney disease. The ordering physician should be mindful of the caveats associated with each biochemical testing. ACTH-dependent Cushing's syndrome can be difficult to diagnose properly in the setting of a negative pituitary MRI. IPSS, although an expensive and invasive test, has the best diagnostic accuracy. This case further demonstrates the importance of performing an IPSS to diagnose CD and distinguish from an ectopic source when imaging is non-diagnostic. Presentation: No date and time listed

Overestimation of the effect of (fos)aprepitant on intravenous dexamethasone pharmacokinetics requires adaptation of the guidelines for children with chemotherapy-induced nausea and vomiting

PurposeChemotherapy-induced nausea and vomiting (CINV) are common side effects in pediatric oncology treatment. Besides 5-HT3-antagonists, both dexamethasone and aprepitant are cornerstone drugs in controlling these side effects. Based on results of adult studies, the dexamethasone dose is reduced by 50% when combined with aprepitant, because of a drug-drug interaction, even though data on the interaction in children is lacking. The current study was developed to investigate the effect of aprepitant on dexamethasone clearance (CL) in children, in order to assess if dexamethasone dose reduction for concomitant use of aprepitant is appropriate in the current antiemetic regimen.MethodsIn total, 65 children (0.6–17.9 years), receiving intravenous or oral antiemetic therapy (dexamethasone ± aprepitant) as standard of care, were included. 305 dexamethasone plasma concentrations were determined using LC–MS/MS. An integrated dexamethasone and aprepitant pharmacokinetic model was developed using non-linear mixed effects modelling in order to investigate the effect of aprepitant administration on dexamethasone CL.ResultsIn this population, dexamethasone CL in patients with concomitant administration of aprepitant was reduced by approximately 30% of the uninhibited CL (23.3 L/h (95% confidence interval 20.4–26.0)). This result is not consistent with the results of adult studies (50% reduction). This difference was not age dependent, but might be related to the route of administration of dexamethasone. Future studies are needed to assess the difference in oral/intravenous dexamethasone.ConclusionWhen dexamethasone is given intravenously as a component of triple therapy to prevent CINV in children, we advise to reduce the dexamethasone dose by 30% instead of 50%.

Vitamin D levels do not cause vitamin-drug interactions with dexamethasone or dasatinib in mice.

Vitamin D3 (VD3) induces intestinal CYP3A that metabolizes orally administered anti-leukemic chemotherapeutic substrates dexamethasone (DEX) and dasatinib potentially causing a vitamin-drug interaction. To determine the impact of VD3 status on systemic exposure and efficacy of these chemotherapeutic agents, we used VD3 sufficient and deficient mice and performed pharmacokinetic and anti-leukemic efficacy studies. Female C57BL/6J and hCYP3A4 transgenic VD3 deficient mice had significantly lower duodenal (but not hepatic) mouse Cyp3a11 and hCYP3A4 expression compared to VD3 sufficient mice, while duodenal expression of Mdr1a, Bcrp and Mrp4 were significantly higher in deficient mice. When the effect of VD3 status on DEX systemic exposure was compared following a discontinuous oral DEX regimen, similar to that used to treat pediatric acute lymphoblastic leukemia patients, male VD3 deficient mice had significantly higher mean plasma DEX levels (31.7 nM) compared to sufficient mice (12.43 nM) at days 3.5 but not at any later timepoints. Following a single oral gavage of DEX, there was a statistically, but not practically, significant decrease in DEX systemic exposure in VD3 deficient vs. sufficient mice. While VD3 status had no effect on oral dasatinib’s area under the plasma drug concentration-time curve, VD3 deficient male mice had significantly higher dasatinib plasma levels at t = 0.25 hr. Dexamethasone was unable to reverse the poorer survival of VD3 sufficient vs. deficient mice to BCR-ABL leukemia. In conclusion, although VD3 levels significantly altered intestinal mouse Cyp3a in female mice, DEX plasma exposure was only transiently different for orally administered DEX and dasatinib in male mice. Likewise, the small effect size of VD3 deficiency on single oral dose DEX clearance suggests that the clinical significance of VD3 levels on DEX systemic exposure are likely to be limited.

Impact of dose and duration of therapy on dexamethasone pharmacokinetics in childhood acute lymphoblastic leukaemia—a report from the UKALL 2011 trial

IntroductionThe use of dexamethasone in acute lymphoblastic leukaemia therapy contributes to short- and long-term toxicities. The UKALL 2011 randomised trial investigated whether a more intense dexamethasone dose (10 mg/m2/d x 14d, short vs 6 mg/m2/d x 28d, standard) would lead to a more rapid cytoreduction and reduced adverse effects associated with longer durations of steroids in induction. The impact of dose and duration on dexamethasone pharmacokinetics was investigated. MethodsBlood samples were obtained on one of the first three and last three days of induction dexamethasone dosing at time points up to 8 h after oral administration. Plasma dexamethasone levels were quantified in 1084 plasma samples obtained from 174 children and a population pharmacokinetic model developed. ResultsDrug exposure varied significantly between patients, with a >12-fold variation in AUC0–12h values and a marked overlap in dexamethasone exposures between dose levels. Intuitively, AUC0–12h was significantly higher with short dosing (10 mg/m2/d), but cumulative exposure was significantly higher with standard dosing over 28 days, after a higher cumulative dose. Concomitant rasburicase administration was associated with a 60% higher dexamethasone clearance. Day 8 bone marrow response was comparable between dosing arms, but those with <5% blast count exhibited a greater mean dexamethasone exposure than those with >5%. No statistical differences were observed between arms in terms of steroid-related toxicity or minimal residual disease at the end of induction. ConclusionThe potential significance of dexamethasone AUC0–12h on early response and higher cumulative exposure on the standard arm suggest that duration of therapy and exposure may be more important factors than absolute dose from a clinical pharmacology perspective.

Change In Albumin Levels During Induction Predicts Survival Outcomes In Adult Acute Lymphoblastic Leukemia

BackgroundAsparaginase is an important component of induction and consolidation chemotherapy for acute lymphoblastic leukemia (ALL). Effective asparagine depletion in adult patients with ALL results in a longer duration of overall survival and disease free survival. Variation in asparaginase activity is in part due to the formation of anti-asparaginase antibodies that inactivate asparaginase and result in inadequate asparagine depletion. In addition, the presence of anti-asparaginase antibodies influences dexamethasone pharmacokinetics by increasing dexamethasone clearance, which has been shown to correlate with a higher risk of relapse. Hypoalbuminemia is a recognized side effect of asparaginase, and has been studied as a measure of asparaginase inhibition of liver protein synthesis. The purpose of this retrospective study was to evaluate the effect of asparaginase activity during induction, using serum albumin as a surrogate marker, on overall outcomes. We hypothesized that patients with lower albumin levels, and thus increased asparaginase activity, would have improved survival. MethodsA retrospective electronic chart review was performed on 108 adult patients with newly diagnosed ALL who underwent induction chemotherapy treatment with Cancer and Leukemia Group B (CALGB) 9511 protocol at Stanford Hospital and Clinics between 2004 and 2012. PEG-asparaginase (2000 units per m2, capped at 3750 units) administration on day 5 of induction was confirmed on the electronic medical administration record. Patients also received therapy per protocol including prednisone (60mg per m2 per day) from days 1 through 21, with the exception of patients >60 years old who received prednisone from days 1 through 7. The primary outcomes measured were median overall survival and disease free survival. Patients were divided based on percent change in albumin level at day 14 of induction, using 20% decrease from pre-treatment baseline as a cut-off. The log rank test was used to calculate differences in survival and the Cox proportional hazards model was used to calculate hazard ratios. Baseline characteristics between the two groups were compared using chi-square or t-test analysis. ResultsA total of 104 patients with newly diagnosed ALL were included in the final analysis (1 patient did not receive PEG-asparaginase and 3 were lost early to follow-up). Of these, 52% were male. The median age was 49 years, and 20% of patients were 60 or older. The majority had B cell ALL (88%). Cytogenetics were normal in 28% of patients; t(9;22) was observed in 28% and t(4;11) in 4%. The induction mortality was 9% and 88% achieved complete remission (CR). In the entire patient population, the median overall survival was 27.4 months, and the median disease free survival was 25.0 months. For the patients who achieved at least a 20% decrease in albumin at day 14 of induction (57 patients), there was a statistically significant difference in median overall survival compared to those who had less than a 20% decrease in albumin, with an overall survival duration of 47.4 months and 15.8 months, respectively (HR = 2.23, P = 0.007). The median duration of disease free survival in those who achieved at least a 20% decrease in albumin at day 14 was 39 months compared to 13 months in those with less than a 20% decrease (HR = 1.93, P = 0.039). There was no statistically significant difference in the rate of CR between the two groups (P = 0.503). There was also no statistically significant difference in the baseline characteristics (age, WBC at diagnosis, presence of Philadelphia chromosome, and proportion of patients who eventually underwent BMT) between the two groups. ConclusionThis study found a correlation between a decrease in albumin levels during induction, which was used as a surrogate measure of asparaginase activity, and duration of overall survival and disease free survival. This suggests that lower albumin levels associated with higher asparaginase activity and adequate asparagine depletion are important predictors of outcomes. Further studies assessing the effect of optimal individualized dosing of asparaginase based on albumin levels and/or asparagine depletion might be helpful to improve outcomes of adult patients with ALL. Disclosures:No relevant conflicts of interest to declare.

Dexamethasone exposure and asparaginase antibodies affect relapse risk in acute lymphoblastic leukemia

AbstractWe have previously hypothesized that higher systemic exposure to asparaginase may cause increased exposure to dexamethasone, both critical chemotherapeutic agents for acute lymphoblastic leukemia. Whether interpatient pharmaco-kinetic differences in dexamethasone contribute to relapse risk has never been studied. The impact of plasma clearance of dexamethasone and anti–asparaginase antibody levels on risk of relapse was assessed in 410 children who were treated on a front-line clinical trial for acute lymphoblastic leukemia and were evaluable for all pharmacologic measures, using multivariate analyses, adjusting for standard clinical and biologic prognostic factors. Dexamethasone clearance (mean ± SD) was higher (P = 3 × 10−8) in patients whose sera was positive (17.7 ± 18.6 L/h per m2) versus nega-tive (10.6 ± 5.99 L/h per m2) for anti–asparaginase antibodies. In multivariate analyses, higher dexamethasone clearance was associated with a higher risk of any relapse (P = .01) and of central nervous system relapse (P = .014). Central nervous system relapse was also more common in patients with anti–asparaginase antibodies (P = .019). In conclusion, systemic clearance of dexamethasone is higher in patients with anti–asparaginase antibodies. Lower exposure to both drugs was associated with an increased risk of relapse.

Systemic Exposure to Dexamethasone and Asparaginase Affects Risk of Relapse in Children with Acute Lymphoblastic Leukemia

Abstract▪2550▪This icon denotes a clinically relevant abstractDexamethasone and asparaginase are key components of acute lymphoblastic leukemia (ALL) treatment. We previously observed that patients with a higher systemic exposure to asparaginase had a lower clearance and thus a higher systemic exposure to dexamethasone (Yang et al, J Clin Oncol; 26:1932–9, 2008). Whether interpatient dexamethasone pharmacokinetic variability contributes to relapse risk is not known. We determined the prognostic influence of dexamethasone plasma clearance and of anti-asparaginase antibody levels on risk of relapse via multivariate analyses after adjusting for standard clinical and biologic prognostic factors (treatment risk arm, age, race, initial leukocyte count, ALL immunophenotype, minimal residual disease and CNS status) in 410 children with ALL who were treated on a front-line clinical trial (St. Jude Total XV) and were evaluable for the pharmacologic measures through at least 22 weeks from diagnosis. Dexamethasone apparent clearance (average ± standard deviation) was significantly (p = 3 ×10−8) higher in patients with detectable serum levels of anti-asparaginase antibodies (17.7 ± 18.6 L/h/m2) compared to patients with no detectable antibodies (10.6 ± 5·99 L/h/m2), consistent with higher exposure to asparaginase being associated with higher exposure to dexamethasone. In multivariate analysis, higher dexamethasone clearance was associated with a higher risk of any relapse (hematologic, CNS, combined, and other; hazard ratio 1.56, 95% confidence interval, 1.1–2.19; p = 0.01) and of any CNS relapse (CNS and CNS + hematologic; hazard ratio 1.93, 95% confidence interval 1.1–3.37; p = 0.02). CNS relapse was also more frequent in patients with vs. those without anti-asparaginase antibodies (5-year cumulative risk of 4.9% vs. 1.8%; p = 0.02). Classification and regression tree analysis revealed that a dexamethasone clearance greater than 37.5 L/h/m2 might distinguish patients at higher risk of relapse (Figure). In conclusion, the presence of anti-asparaginase antibodies is associated with increased systemic clearance of dexamethasone. Lower exposure to dexamethasone and asparaginase are associated with an increased risk of relapse in children with ALL treated with contemporary therapy. [Display omitted] The cumulative incidence of any relapse (A) and CNS relapse (B) was higher in patients with dexamethasone (Dex) clearance (CL) greater than 37.5 L/h/m2 than in those with lower clearance (p values based on log rank test). Disclosures:Evans:St. Jude Children’s research Hospital: Employment, Patents & Royalties; NIH & NCI: Research Funding; Aldagen: Membership on an entity’s Board of Directors or advisory committees. Relling:Sigma-Tau Pharmaceuticals, Inc: Investigator-initiated research; NIH: Research Funding; St. Jude Children’s Research Hospital: Employment, Patents & Royalties.

Osteonecrosis in childhood ALL

Kawedia et al report a 71% incidence of osteonecrosis (ON) in a cohort of children and young adult acute lymphoblastic leukemia (ALL) patients who underwent routine magnetic resonance imaging (MRI) screening at various time points on study. A majority of cases were asymptomatic. Older age, increased treatment intensity, low serum albumen, elevated lipid levels, and decreased dexamethasone clearance were risk factors associated with an increased incidence of osteonecrosis.

Pharmacokinetic, pharmacodynamic, and pharmacogenetic determinants of osteonecrosis in children with acute lymphoblastic leukemia

AbstractOsteonecrosis is a severe glucocorticoid-induced complication of acute lymphoblastic leukemia treatment. We prospectively screened children (n = 364) with magnetic resonance imaging of hips and knees, regardless of symptoms; the cumulative incidence of any (grade 1-4) versus symptomatic (grade 2-4) osteonecrosis was 71.8% versus 17.6%, respectively. We investigated whether age, race, sex, acute lymphoblastic leukemia treatment arm, body mass, serum lipids, albumin and cortisol levels, dexamethasone pharmacokinetics, and genome-wide germline genetic polymorphisms were associated with symptomatic osteonecrosis. Age more than 10 years (odds ratio, = 4.85; 95% confidence interval, 2.5-9.2; P = .00001) and more intensive treatment (odds ratio = 2.5; 95% confidence interval, 1.2-4.9; P = .011) were risk factors and included as covariates in all analyses. Lower albumin (P = .05) and elevated cholesterol (P = .02) associated with symptomatic osteonecrosis, and severe (grade 3 or 4) osteonecrosis was linked to poor dexamethasone clearance (P = .0005). Adjusting for clinical features, polymorphisms of ACP1 (eg, rs12714403, P = 1.9 × 10−6, odds ratio = 5.6; 95% confidence interval, 2.7-11.3), which regulates lipid levels and osteoblast differentiation, were associated with risk of osteonecrosis as well as with lower albumin and higher cholesterol. Overall, older age, lower albumin, higher lipid levels, and dexamethasone exposure were associated with osteonecrosis and may be linked by inherited genomic variation.

Mechanisms of dexamethasone-induced disturbed sleep and fatigue in paediatric patients receiving treatment for ALL

Background Dexamethasone contributes to high cure rates in paediatric acute lymphoblastic leukaemia (ALL) but significantly and adversely alters sleep and fatigue. Herein we explored three mechanisms (pharmacokinetics, serum albumin and pharmacogenetics) through which dexamethasone may cause debilitating fatigue and disrupted sleep. Methods We enrolled 100 patients on a 10-d study: 5-d of no dexamethasone (OFF DEX) followed by 5-d of dexamethasone (ON DEX) during continuation chemotherapy. Sleep variables were collected with continuous actigraphy on days 1 through 5, both OFF DEX and ON DEX. On days 2 and 5 of each 5-d period, parents and patients 7 years of age and older completed a sleep diary and Fatigue Scale questionnaire. Blood was collected at 0 (pre-dexamethasone), 1, 2, 4 and 8 h after the first oral dexamethasone dose for pharmacokinetic analysis. Serum albumin concentration was retrospectively analysed in stored samples. Patient DNA was genotyped for 99 polymorphic loci in candidate genes associated with glucocorticoid metabolism. Results Dexamethasone clearance was significantly greater in younger patients than in older ones and in lower risk patients. In multiple regression models, risk group was significantly related to pharmacokinetic parameters. We found that polymorphisms in three genes (AHSG, IL6, POLDIP3) were significantly associated with sleep measures but not with fatigue. Conclusion Risk group had the most significant relationship with disrupted sleep in patients while on dexamethasone. Serum albumin levels had neither a direct relationship with sleep or fatigue variables nor an indirect relationship through systemic exposure to dexamethasone. We identified candidate genes that may help explain the adverse events of disrupted sleep in paediatric patients receiving dexamethasone.

Dexamethasone as a probe for vinorelbine clearance

To assess the value of using dexamethasone as an in vivo probe for predicting vinorelbine clearance (CL). A population approach (implemented with NONMEM) was used to analyse blood vinorelbine pharmacokinetic data from 20 patients who received a 20-min intravenous infusion of vinorelbine (from 20 to 30 mg m(-2)). Selected patient clinical data as well as known functional single CYP3A5 and ABCB1 genotype were also tested as covariates. The best covariate model (with +/- 95% confidence intervals) was based on dexamethasone plasma clearance (DPC) and alkaline phosphatase (ALP): vinorelbine blood CL (l h(-1)) = 39.8(+/- 4.0) x (DPC/13.2)(0.524(+/-0.322)) x (ALP/137)(-0.198(+/-0.158)). Interindividual variability in vinorelbine CL decreased from 29.7% (model without covariate) to 14.7% when including DPC and ALP. Vinorelbine CL was not correlated with body surface area (BSA) or associated with CYP3A5 and ABCB1 genotype. These results indicate that individualization of vinorelbine dose would be improved by using dexamethasone clearance rather than BSA. Dexamethasone merits further evaluation as a probe of CYP3A metabolism.

Dexamethasone metabolism in dexamethasone suppression test suppressors and nonsuppressors

Background: Variable dexamethasone kinetics is a possible confound in the dexamethasone suppression test. Modifications to include dexamethasone plasma levels and specific dexamethasone “windows” have been proposed. Our study aims to validate our proposed dexamethasone windows in an independent sample of 121 subjects. Methods: We performed dexamethasone suppression tests in 162 subjects with mixed psychiatric diagnoses. Dexamethasone levels and β-phase half-life of dexamethasone were computed for suppressors and nonsuppressors. Results: Dexamethasone levels were lower in nonsuppressors than in suppressors. Dexamethasone levels correlated inversely with cortisol levels in the total sample, but were nonsignificant or weakly associated in those samples restricted to the windows. The β-phase half-life of dexamethasone was shorter in nonsuppressors. The dexamethasone windows were validated at 3:00 pm and 10:00 pm. We propose 4.0 ng/mL as a revised upper limit of the 8:00 am dexamethasone window. Conclusions: The plasma dexamethasone level is confirmed as a confound in the dexamethasone suppression test through more rapid dexamethasone clearance in nonsuppressors. Application of dexamethasone windows will reduce this source of test variance.

Circulating concentration of dexamethasone in healthy dogs, dogs with hyperadrenocorticism, and dogs with nonadrenal illness during dexamethasone suppression testing

Summary Concentration of dexamethasone was determined in plasma or serum samples from dogs after iv administration of a low dose (0.01 mg/kg of body weight) or high dose (0.1 mg/kg) of dexamethasone. On the basis of history, clinical signs of disease, and degree of cortisol suppression in response to dexamethasone, dogs were assigned to these groups: healthy dogs, dogs with nonadrenal illness, and dogs with hyperadrenocorticism. Four hours after administration of the low dose of dexamethasone, concentration of the steroid was reduced (P &lt; 0.05) in dogs with hyperadrenocorticism, compared with healthy dogs, but not compared with values from dogs with nonadrenal illness. By 8 hours after dexamethasone administration, values were similar across groups. Dexamethasone concentration 4 and 8 hours after high-dose administration was similar between healthy dogs and dogs with hyperadrenocorticism. Concentration of dexamethasone 4 and 8 hours after its administration overlapped after the 2 doses. For example, in 11 of 66 dogs from all groups, concentration measured 4 hours after the low dose was greater than the minimal concentration determined in the 18 dogs given the high dose. These data indicate that dexamethasone metabolism may be altered in dogs with hyperadrenocorticism, and that individuals may have appreciable variability in dexamethasone clearance. Such variability provides a possible explanation for false-positive and false-negative results associated with dexamethasone suppression testing in dogs.

A longitudinal evaluation of dexamethasone pharmacokinetics in depressed patients and normal controls : Sally K. Guthrie, Pharm. D., Michael Heidt, B.S., Atul Pande, M.D., Leon Grunhaus, M.D., Roger Haskett, M.D., M. Hariharan, Ph.D. College of Pharmacy and Department of Psychiatry, Medical School, University of Michigan, Ann Arbor, MI 48109-1065

Ten depressed patients and eight control subjects received 1 mg of dexamethasone intravenously at two different time points. Depressed patients were studied when they were depressed and following an improvement in their depression. In control subjects the first and second studies were performed approximately 1 month apart. Dexamethasone and cortisol were determined at 0, 5, 15, and 30 minutes, then at 1, 1.2, 2, 3, 4, 5, 6, 7, 9, 12, 17, and 24 hours following dexamethasone administration. Data from each patient was fit using a computer to a two compartment pharmacokinetic model and area under the time versus plasma concentration curve, elimination half-life, and clearance were also determined. Depressed patients exhibited a slower dexamethasone clearance and a larger area under the curve than control subjects at the first time point, but not at the second time point. The groups did not differ significantly in any of the other pharmacokinetic parameters (including distribution half-life, elimination half-life, or volume of distribution) at either time point. The possible causes and implications of these findings are discussed.

Cushing's Disease With 'Normal Suppression' due to Decreased Dexamethasone Clearance

Suppression of urinary corticosteroids during low-dose dexamethasone testing (0.5 mg every six hours eight times) has commonly been recognized as a response that excludes the diagnosis of Cushing's syndrome. Although "normal suppression" has been reported previously in Cushing's disease, rarely has an explanation been provided for this aberrant response. We report a case of proven Cushing's disease in which normal suppression was observed with low-dose dexamethasone testing. Further study suggested that this phenomenon, which is not widely recognized, was related to an abnormally decreased clearance of dexamethasone. We therefore suggest that whenever responses to testing appear discordant with the clinical index of suspicion, simultaneous plasma dexamethasone and cortisol levels should be obtained to exclude abnormalities in dexamethasone clearance.

Cushing's disease with 'normal suppression' due to decreased dexamethasone clearance

Cushing's disease with 'normal suppression' due to decreased dexamethasone clearance