Exploratory evaluation of pharmacodynamics,pharmacokinetics and safety of rivaroxaban in children and adolescents: an EINSTEIN-Jr phase I study

Background

The EINSTEIN-Jr program will evaluate rivaroxaban for the treatment of venous thromboembolism (VTE) in children, targeting exposures similar to the 20 mg once-daily dose for adults.

Methods

This was a multinational, single-dose, open-label, phase I study to describe the pharmacodynamics (PD), pharmacokinetics (PK) and safety of a single bodyweight-adjusted rivaroxaban dose in children aged 0.5–18 years. Children who had completed treatment for a venous thromboembolic event were enrolled into four age groups (0.5–2 years, 2–6 years, 6–12 years and 12–18 years) receiving rivaroxaban doses equivalent to 10 mg or 20 mg (either as a tablet or oral suspension). Blood samples for PK and PD analyses were collected within specified time windows.

Results

Fifty-nine children were evaluated. In all age groups, PD parameters (prothrombin time, activated partial thromboplastin time and anti-Factor Xa activity) showed a linear relationship versus rivaroxaban plasma concentrations and were in line with previously acquired adult data, as well as in vitro spiking experiments. The rivaroxaban pediatric physiologically based pharmacokinetic model, used to predict the doses for the individual body weight groups, was confirmed. No episodes of bleeding were reported, and treatment-emergent adverse events occurred in four children and all resolved during the study.

Conclusions

Bodyweight-adjusted, single-dose rivaroxaban had predictable PK/PD profiles in children across all age groups from 0.5 to 18 years. The PD assessments based on prothrombin time and activated partial thromboplastin time demonstrated that the anticoagulant effect of rivaroxaban was not affected by developmental hemostasis in children.

Trial registration

ClinicalTrials.gov number, NCT01145859.

     

Combination of acquired von Willebrand syndrome (AVWS) and Glanzmann thrombasthenia in monoclonal gammopathy of uncertain significance (MGUS), a case report

Background

Autoimmune paraphenomena, are associated with B-cell lymphoproliferative disorders, including monoclonal gammopathy of uncertain significance. These paraphenomena can rarely include acquired bleeding disorders.

Case presentation

This case study reports an unusual clinical presentation of 2 acquired bleeding disorders, Acquired von Willebrand syndrome (disease) and Acquired Glanzmann’s thrombasthenia, in an elderly patient with monoclonal gammopathy of uncertain significance.

Conclusions

Acquired bleeding disorders are often underdiagnosed and a high degree of clinical suspicion is required. The patient in this study demonstrated platelet aggregometry which was atypical for isolated Glanzmann’s thrombosthenia because of the severe concomitant endogenous decrease in von Willebrand factor. There was an absence of platelet aggregation to all tested agonists including ristocetin. Once the diagnosis was made, however, the patient showed a partial response to intravenous immunoglobulin confirming the immunological pathogenesis in this case. This case highlights the need to consider acquired bleeding disorders in patients with a possible predisposing factor.

     

Relapsing Painful Ophthalmoplegic Neuropathy: No longer a “Migraine,” but Still a Headache

Purpose of Review

Recurrent painful ophthalmoplegic neuropathy (RPON), formerly known as ophthalmoplegic migraine, is an uncommon disorder with repeated episodes of ocular cranial nerve neuropathy associated with ipsilateral headache. This review discusses the clinical presentation, current understanding of the pathophysiology, key differential diagnoses, and evaluation and treatment of RPON.

Recent Findings

The literature is limited due to the rarity of the disorder. Recent case reports and series continue to suggest the age of first attack is most often during childhood or adolescence as well as a female predominance. Multiple recent case reports and series demonstrate focal enhancement of the affected cranial nerve, as the nerve root exits the brainstem. This finding contributed to the current classification of the disorder as a neuropathy, with the present understanding that it is due to a relapsing-remitting inflammatory or demyelinating process. The link to migraine remains a cause of disagreement in the literature.

Summary

RPON is a complex disorder with features of inflammatory neuropathy and an unclear association with migraine. Regardless, the overall prognosis is good for individual episodes, but permanent nerve damage may accumulate with repeated attacks. A better understanding of the pathogenesis is needed to clarify whether it truly represents a single disorder and to guide its treatment. Until that time, a combined approach with acute and preventive therapies can mitigate acute symptoms as well as attempt to limit recurrence of this disabling syndrome.

     

SUNCT and SUNA: an Update and Review

Purpose of Review

The purpose of this review is to provide an update on the clinical features, diagnosis, pathogenesis, epidemiology, and treatment of the rare primary headache disorders short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) and short-lasting unilateral neuralgiform headache attacks with autonomic symptoms (SUNA). Together these entities are known as short-lasting unilateral neuralgiform headache attacks (SUNHA).

Recent Findings

Recent case reports of secondary SUNCT and SUNA due to medullary infarcts support the theory that the trigeminohypothalamic pathway is involved in the pathophysiology of SUNHA. While medical therapy for SUNHA has not significantly changed, surgical therapy for refractory SUNCT and SUNA has made advancements with a recent case series demonstrating the efficacy of deep brain stimulation.

Summary

We will discuss the pathophysiology of both the pain and the autonomic symptoms experienced in SUNCT and SUNA attacks as well the medical, procedural, and surgical options for treatment with emphasis on recent advances. Specific secondary causes reported in the recent literature will be discussed in brief.

     

Headaches in Patients with Pituitary Tumors: a Clinical Conundrum

Purpose of Review

Pituitary tumors account for approximately 17% of all intracranial neoplasms, with the majority being pituitary adenomas. Often, these are found incidentally during a workup for headache; however, the relationship between symptom and pathology remains unclear. The purpose of this article is to review the most recent literature on the epidemiology, pathophysiology, and management of headaches in patients with pituitary tumors.

Recent Findings

The current literature is limited, with few prospective trials focusing on this question. With the exception of pituitary apoplexy, the relationship between headaches and pituitary masses remains unclear. Intervention does not always improve headache and can lead to development of new headache syndromes.

Summary

Further research is needed to better elucidate the relationship between pituitary tumors and headaches. Headache alone is rarely an indication for surgical management of a pituitary adenoma.

     

Radio Frequency Ablation and Pulsed Radiofrequency for Treating Peripheral Neuralgias

Purpose of Review

Peripheral nerve pain is common among patients with typical management including the use of pain medications, neuropathic agents, steroid injections, and nerve blocks. Additionally, the use of pulsed radiofrequency (PRF) and radiofrequency ablation (RFA) can be used in the management of chronic peripheral nerve pain. Previous studies investigating the effectiveness of RFA and PRF, typically case reports, have demonstrated that peripheral nerve RFA and PRF have the potential to provide relief of chronic pain for long duration. Our study aimed at testing efficacy of RFA/PRF for treating peripheral neuralgia. This was a retrospective review. We identified 16 patients who received 17 RFAs/PRFs. Outcomes of interest collected included pain scores before and after procedures, percent improvement in pain after each procedure, and duration of improvement until the time of data collection. In addition, demographic data including age, sex, and nerves involved were collected.

Recent Findings

Eleven patients (12 RFAs/PRFs) (80%) reported improvement after their procedure. Pain scores improved significantly from 6.3?±?2.3 before each procedure to 3.6?±?2.7 after each procedure (p?=?0.003). Eleven patients (12 RFAs/PRFs) reported an average improvement of 60.8%?±?35% after their procedure with an average duration of improvement of 128.8?±?106.8 days.

Summary

RFA and PRF can be used to treat chronic peripheral pain after conservative methods fail to do so. Large clinical trials are needed to confirm our finding.

     

Psychological Characteristics of Chronic Pain: a Review of Current Evidence and Assessment Tools to Enhance Treatment

Purpose of Review

The complicated nature of chronic pain involves an interplay between psychological and physical factors, often resulting in increased emotional distress and reduced quality of life. This review is designed to help the medical practitioner who is working with chronic pain patients to be aware of psychological assessment techniques that can add to comprehensive patient understanding and more effectively guide treatment. Enhanced ability to assess and understand the emotional life of the chronic pain patient provides a basis for intervening and treating more successfully.

Recent Findings

There are a broad range of assessment techniques, some of which require a background in psychology and some that do not, that can identify psychological differences in chronic pain patients and serve to guide intervention strategies. Chronic pain is often comorbid with depression, anxiety, catastrophizing, and various ineffective coping strategies. Some patients, however, have demonstrated more adaptive and effective strategies for cognitively and behaviorally coping with pain and normalizing their lives. Proper assessment enables the individualization of treatment to overcome and/or build upon each patient’s psychological frame of mind to maximize the potential for effective functioning.

Summary

The use of standardized and documented psychological assessment techniques can lead to a better understanding of chronic pain patients and contribute in ways that can enhance response to medical treatment and improve quality of life. It is recommended that certain psychological tools be included to supplement the medical assessment of patients who have chronic pain. A basic assessment can include a short psychological-based clinical interview along with brief measures of depression, anxiety, and coping strategies. It is also recommended that the pain physician have access to professional psychological practitioners as a resource for more complicated assessments and psychological intervention services.

     

Migraine and the Hippocampus

Purpose of Review

The hippocampus is involved in pain processing, pain-related attention and anxiety, and stress response. The present review compiles the present knowledge of hippocampal volume, activity, and connectivity regarding migraine.

Recent Findings

For hippocampal volume, a longitudinal study discovered decreased volume in newly diagnosed migraine patients after 1 year. Two cross-sectional studies suggested an adaptive increase of volume at low headache frequency and a maladaptive decrease of volume at higher headache frequency. Patients who carried a COMT Val homozygous were found to have larger hippocampi on both sides compared with healthy controls with the same polymorphism. For hippocampal activation, one study showed greater nociceptive activation in patients with migraine compared to healthy controls, with the activity correlated to headache frequency. Another study showed greater deactivation and higher functional connectivity linked to other pain-processing regions in low frequency compared to high-frequency migraineurs. At resting state, intraregional functional connectivity of hippocampus was demonstrated to be lower, and connectivity of the hippocampus with other brain regions was different in patients carrying specific genetic variants. For structural connectivity, two studies suggest a stronger connectivity between the hippocampus and other corticolimbic regions, and the altered connectivities are responsible for migraine-associated allodynia or placebo effect of migraine.

Summary

Factors including headache frequency, accumulative number of migraine attacks, anxiety score, depression score, and genetic variants are related to hippocampal morphology and functional changes in people with migraine. Future studies should select participants precisely and appropriately control for genetic variants to investigate the complex relationship between the hippocampus and migraine.

     

Ferumoxytol Is Not Retained in Kidney Allografts in Patients Undergoing Acute Rejection

Purpose

To evaluate whether ultrasmall superparamagnetic iron oxide nanoparticle (USPIO)-enhanced magnetic resonance imaging (MRI) can detect allograft rejection in pediatric kidney transplant patients.

Procedures

The USPIO ferumoxytol has a long blood half-life and is phagocytosed by macrophages. In an IRB-approved single-center prospective clinical trial, 26 pediatric patients and adolescents (age 10–26 years) with acute allograft rejection (n = 5), non-rejecting allografts (n = 13), and normal native kidneys (n = 8) underwent multi-echo T2* fast spoiled gradient-echo (FSPGR) MRI after intravenous injection (p.i.) of 5 mg Fe/kg ferumoxytol. T2* relaxation times at 4 h p.i. (perfusion phase) and more than 20 h p.i. (macrophage phase) were compared with biopsy results. The presence of rejection was assessed using the Banff criteria, and the prevalence of macrophages on CD163 immunostains was determined based on a semi-quantitative scoring system. MRI and histology data were compared among patient groups using t tests, analysis of variance, and regression analyses with a significance threshold of p < 0.05.

Results

At 4 h p.i., mean T2* values were 6.6 ± 1.5 ms for native kidneys and 3.9 ms for one allograft undergoing acute immune rejection. Surprisingly, at 20–24 h p.i., one rejecting allograft showed significantly prolonged T2* relaxation times (37.0 ms) compared to native kidneys (6.3 ± 1.7 ms) and non-rejecting allografts (7.6 ± 0.1 ms). Likewise, three additional rejecting allografts showed significantly prolonged T2* relaxation times compared to non-rejecting allografts at later post-contrast time points, 25–97 h p.i. (p = 0.008). Histological analysis revealed edema and compressed microvessels in biopsies of rejecting allografts. Allografts with and without rejection showed insignificant differences in macrophage content on histopathology (p = 0.44).

Conclusion

After ferumoxytol administration, renal allografts undergoing acute rejection show prolonged T2* values compared to non-rejecting allografts. Since histology revealed no significant differences in macrophage content, the increasing T2* value is likely due to the combined effect of reduced perfusion and increased edema in rejecting allografts.

     

Modeling Dynamic Contrast-Enhanced MRI Data with a Constrained Local AIF

Purpose

This study aims to develop a constrained local arterial input function (cL-AIF) to improve quantitative analysis of dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) data by accounting for the contrast-agent bolus amplitude error in the voxel-specific AIF.

Procedures

Bayesian probability theory-based parameter estimation and model selection were used to compare tracer kinetic modeling employing either the measured remote-AIF (R-AIF, i.e., the traditional approach) or an inferred cL-AIF against both in silico DCE-MRI data and clinical, cervical cancer DCE-MRI data.

Results

When the data model included the cL-AIF, tracer kinetic parameters were correctly estimated from in silico data under contrast-to-noise conditions typical of clinical DCE-MRI experiments. Considering the clinical cervical cancer data, Bayesian model selection was performed for all tumor voxels of the 16 patients (35,602 voxels in total). Among those voxels, a tracer kinetic model that employed the voxel-specific cL-AIF was preferred (i.e., had a higher posterior probability) in 80 % of the voxels compared to the direct use of a single R-AIF. Maps of spatial variation in voxel-specific AIF bolus amplitude and arrival time for heterogeneous tissues, such as cervical cancer, are accessible with the cL-AIF approach.

Conclusions

The cL-AIF method, which estimates unique local-AIF amplitude and arrival time for each voxel within the tissue of interest, provides better modeling of DCE-MRI data than the use of a single, measured R-AIF. The Bayesian-based data analysis described herein affords estimates of uncertainties for each model parameter, via posterior probability density functions, and voxel-wise comparison across methods/models, via model selection in data modeling.