Rivaroxaban reversal with prothrombin complex concentrate or tranexamic acid in healthy volunteers

Essentials Specific reversal agents for managing severe factor Xa inhibitor-associated bleeding are lacking. We assessed 4-factor-prothrombin complex concentrate (4F-PCC) and tranexamic acid (TXA). 4F-PCC, but not TXA, reduced the prothrombin time and increased endogenous thrombin potential. These agents may be viable options for reversal of therapeutic doses of rivaroxaban.

SUMMARY

Background Oral activated factor X inhibitors such as rivaroxaban are widely used, but specific reversal agents are lacking. Although four-factor prothrombin complex concentrate (4F-PCC) and tranexamic acid (TXA) are sometimes used to manage serious bleeding, their efficacy is unknown. Prior studies in healthy subjects taking rivaroxaban revealed that 4F-PCC partially reverses the prolonged prothrombin time (PT), and fully restores the endogenous thrombin potential (ETP). The effect of TXA has not been evaluated. Methods In this double-blind, parallel-group study, 147 healthy volunteers given rivaroxaban 20 mg twice daily for 3 days were randomized after their morning dose on day 4 to receive intravenous 4F-PCC (50 IU kg-1 ), TXA (1.0 g), or saline. Standardized punch biopsies were performed at baseline and after 4F-PCC, TXA or saline administration. Reversal was assessed by measuring bleeding duration and bleeding volume at biopsy sites, and by determining the PT and ETP. Results As compared with saline, 4F-PCC partially reversed the PT and completely reversed the ETP, whereas TXA had no effect. Neither 4F-PCC nor TXA reduced bleeding duration or volume. All treatments were well tolerated, with no recorded adverse events. Conclusions Although 4F-PCC reduced the PT and increased the ETP in volunteers given supratherapeutic doses of rivaroxaban, neither 4F-PCC nor TXA influenced punch biopsy bleeding.

Comparison of three-factor and four-factor prothrombin complex concentrates regarding reversal of the anticoagulant effects of rivaroxaban in healthy volunteers

BACKGROUND

Four-factor prothrombin complex concentrates (PCCs), which contain factor II, FVII, FIX, and FX, have shown the potential to reverse the anticoagulant effect of rivaroxaban in healthy volunteers. The purpose of this study was to determine whether a three-factor PCC, which contains little FVII, has a similar effect.

METHODS AND RESULTS

We performed an open-label, single-center, parallel-group study comparing the effect of a three-factor PCC (Profilnine SD) with that of a four-factor PCC (Beriplex P/N) on the pharmacodynamics of rivaroxaban in 35 healthy volunteers. After receiving 4 days of rivaroxaban 20 mg twice daily to obtain supratherapeutic steady-state concentrations, volunteers were randomized to receive a single 50 IU kg(-1) bolus dose of four-factor PCC, three-factor PCC or saline 4 h after the morning dose of rivaroxaban on day 5, and the effects of these interventions on prothrombin time and thrombin generation were determined. Within 30 min, four-factor PCC reduced mean prothrombin time by 2.5-3.5 s, whereas three-factor PCC produced only a 0.6-1.0-s reduction. In contrast, three-factor PCC reversed rivaroxaban-induced changes in thrombin generation more than four-factor PCC.

CONCLUSIONS

This study demonstrates the potential of both three-factor and four-factor PCCs to at least partially reverse the anticoagulant effects of rivaroxaban in healthy adults. The discrepant effects of the PCC preparations may reflect differences in the procoagulant components present in each.

Population pharmacokinetics and pharmacodynamics of rivaroxaban in patients with non-valvular atrial fibrillation: results from ROCKET AF

Two once-daily rivaroxaban dosing regimens were compared with warfarin for stroke prevention in patients with non-valvular atrial fibrillation in ROCKET AF: 20 mg for patients with normal/mildly impaired renal function and 15 mg for patients with moderate renal impairment. Rivaroxaban population pharmacokinetic (PK)/pharmacodynamic (PD) modeling data from ROCKET AF patients (n = 161) are reported and are used to confirm established rivaroxaban PK and PK/PD models and to re-estimate values of the models' parameters for the current AF population. An oral one-compartment model with first-order absorption adequately described rivaroxaban PK. Age, renal function, and lean body mass influenced the PK model. Prothrombin time and prothrombinase-induced clotting time exhibited a near-linear relationship with rivaroxaban plasma concentration; inhibitory effects were observed through to 24 hours post-dose. Rivaroxaban plasma concentration and factor Xa activity had an inhibitory maximum-effect (Emax ) relationship. Renal function (on prothrombin time; prothrombinase-induced clotting time) and age (on factor Xa activity) had moderate effects on PK/PD models. PK and PK/PD models were shown to be adequate for describing the current dataset. These findings confirm the modeling and empirical results that led to the selection of doses tested against warfarin in ROCKET AF.

X-ray emission spectroscopy of cerium across the γ-α volume collapse transition

High-pressure x-ray emission measurements are used to provide crucial evidence in the longstanding debate over the nature of the isostructural (α, γ) volume collapse in elemental cerium. Extended local atomic model calculations show that the satellite of the Lγ emission line offers direct access to the total angular momentum observable (J(2)). This satellite experiences a 30% steplike decrease across the volume collapse, validating the Kondo model in conjunction with previous measurements. Direct comparisons are made with previous predictions by dynamical mean field theory. A general experimental methodology is demonstrated for analogous work on a wide range of strongly correlated f-electron systems.

Solid debris collection for radiochemical diagnostics at the National Ignition Facility

Radiochemical analysis of post-ignition debris inside the National Ignition Facility (NIF) target chamber can help determine various diagnostic parameters associated with the implosion efficiency of the fusion capsule. This technique is limited by the ability to distinguish ablator material from other debris and by the collection efficiency of the capsule debris after implosion. Prior to designing an on-line collection system, the chemical nature and distribution of the debris inside the chamber must be determined. The focus of our current work has been on evaluating capture of activated Au hohlraum debris on passive foils (5 cm diameter, 50 cm from target center) post-shot. Preliminary data suggest that debris distribution is locally heterogeneous along the equatorial and polar line-of-sights.

Diffusionless γ⇄α phase transition in polycrystalline and single-crystal cerium

The cerium γ⇄α transition was investigated using high-pressure, high-temperature angle-dispersive x-ray diffraction measurements on both poly- and single-crystalline samples, explicitly addressing symmetry change and transformation paths. The isomorphic hypothesis of the transition is confirmed, with a transition line ending at a solid-solid critical point. The critical exponent is determined, showing a universal behavior that can be pictured as a liquid-gas transition. We further report an isomorphic transition between two single crystals (with more than 14% of volume difference), an unparalleled observation in solid-state matter interpreted in terms of dislocation-induced diffusionless first-order phase transformation.

Emergence of strong exchange interaction in the actinide series: the driving force for magnetic stabilization of curium

Using electron energy-loss spectroscopy, many-electron atomic spectral calculations, and density functional theory, we show that angular-momentum coupling in the 5f states plays a decisive role in the formation of the magnetic moment in Cm metal. The 5f states of Cm in intermediate coupling are strongly shifted towards the LS coupling limit due to exchange interaction, unlike most actinide elements where the effective spin-orbit interaction prevails. Hund's rule coupling is the key to producing the large spin polarization that dictates the newly found crystal structure of Cm under pressure.

Symmetry and stability of plutonium: the influence of electronic structure

Using first-principles density-functional theory, we calculate the bond strengths between the 12 nearest neighbors in delta plutonium for both pure Pu and a Pu-3.7 at. % Ga alloy. Our results for pure Pu reveal a structure with the monoclinic space group Cm rather than face-centered cubic Fm3m, showing that the anomalously large anisotropy of delta plutonium is a consequence of greatly varying bond strengths between the 12 nearest neighbors. Further results for a Pu-3.7 at. % Ga alloy show that the nearest-neighbor bond strengths around a Ga atom are more uniform. Hence, our calculations address (i) why the ground state of Pu is monoclinic, (ii) why distortions of the delta phase are viable, with considerable implications for the behavior of the material as it ages due to anisotropic response to self-irradiation, and (iii) why Ga stabilizes face-centered cubic delta-Pu.

Probing the population of the spin-orbit split levels in the actinide 5f states

Spin-orbit interaction in the 5f states is believed to strongly influence exotic behaviors observed in actinide metals and compounds. Understanding these interactions and how they relate to the actinide series is of considerable importance. To address this issue, the branching ratio of the white-line peaks of the N4,5 edge for the light actinide metals, alpha-Th, alpha-U, and alpha-Pu were recorded using electron energy-loss spectroscopy (EELS) in a transmission electron microscope (TEM) and synchrotron-radiation-based X-ray absorption spectroscopy (XAS). Using the spin-orbit sum rule and the branching ratios from both experimental spectra and many-electron atomic spectral calculations, accurate values of the spin-orbit interaction, and thus the relative occupation of the j = 5/2 and 7/2 levels, are determined for the actinide 5f states. Results show that the spin-orbit sum rule works very well with both EELS and XAS spectra, needing little or no correction. This is important, since the high spatial resolution of a TEM can be used to overcome the problems of single-crystal growth often encountered with actinide metals, allowing acquisition of EELS spectra, and subsequent spin-orbit analysis, from nm-sized regions. The relative occupation numbers obtained by our method have been compared with recent theoretical results and they show a good agreement in their trend.

Applicability of the spin-orbit sum rule for the actinide 5f states

The branching ratio of core-valence transitions in electron energy-loss spectroscopy and x-ray absorption spectroscopy is linearly related to the expectation value of the spin-orbit operator of the valence states. Here, we analyze the branching ratio of the N(4,5) edges in the actinides and find that the spin-orbit sum rule gives an accurate result without the need to include the core-valence interactions. The branching ratio is not only useful to study the variations in the 5f spin-orbit interaction, it also allows us to constrain the 5f count for given angular-momentum coupling conditions.

Failure of Russell-Saunders coupling in the 5f states of plutonium

Using high energy-electron energy loss spectroscopy, transmission electron microscopy, and synchrotron-radiation-based x-ray absorption spectroscopy, we provide the first experimental evidence that Russell-Saunders (LS) coupling fails for the 5f states of Pu. These results support the assumption that only the use of jj or intermediate coupling is appropriate for the 5f states of Pu. High energy-electron energy loss spectroscopy experiments were performed by use of a transmission electron microscope and are coupled with image and diffraction data; therefore, the measurements are completely phase specific.

A tilting procedure to enhance compositional contrast and reduce residual diffraction contrast in energy-filtered TEM imaging of planar interfaces

This paper systematically demonstrates that energy-filtered transmission electron microscope (EFTEM) images of a planar interface between two single crystals have increased compositional contrast and decreased residual diffraction contrast when the sample is oriented so that the electron beam is parallel to the interface, but not directly on a zone axis. This off-axis orientation reduces diffraction contrast in the unfiltered (and zero-loss) image, which in turn, reduces residual diffraction contrast in single energy-filtered TEM (EFTEM) images, thickness maps, jump-ratio images, and elemental maps. Most importantly, this procedure produces EFTEM images that are more directly interpretable and, in most cases, possess superior spatial resolution compared to EFTEM images acquired directly on a zone axis.

Mechanistic studies of (porphinato)iron-catalyzed isobutane oxidation. Comparative studies of three classes of electron-deficient porphyrin catalysts

We report herein a comprehensive study of (porphinato)iron [PFe]-catalyzed isobutane oxidation in which molecular oxygen is utilized as the sole oxidant; these catalytic reactions were carried out and monitored in both autoclave reactors and sapphire NMR tubes. In situ 19F and 13C NMR experiments, coupled with GC analyses and optical spectra obtained from the autoclave reactions have enabled the identification of the predominant porphyrinic species present during PFe-catalyzed oxidation of isobutane. Electron-deficient PFe catalysts based on 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin [(C6F5)4PH2], 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(pentafluorophenyl) porphyrin [Br8(C6F5)4PH2], and 5,10,15,20-tetrakis(heptafluoropropyl) porphyrin [(C3F7)4PH2] macrocycles were examined. The nature and distribution of hydrocarbon oxidation products show that an autoxidation reaction pathway dominates the reaction kinetics, consistent with a radical chain process. For each catalytic system examined, PFeII species were shown not to be stable under moderate O2 pressure at 80 degrees C; in every case, the PFeII catalyst precursor was converted quantitatively to high-spin PFeIII complexes prior to the observation of any hydrocarbon oxidation products. Once catalytic isobutane oxidation is initiated, all reactions are marked by concomitant decomposition of the porphyrin-based catalyst. In situ 17O NMR spectroscopic studies confirm the incorporation of 17O from labeled water into the oxidation products, implicating the involvement of PFe-OH in the catalytic cycle. Importantly, Br8(C6F5)4PFe-based catalysts, which lack macrocycle C-H bonds, do not exhibit augmented stability with respect to analogous catalysts based on (C6F5)4PFe and (C3F7)4PFe species. The data presented are consistent with a hydrocarbon oxidation process in which PFe complexes play dual roles of radical chain initiator, and the species responsible for the catalytic decomposition of organic peroxides. This modified Haber-Weiss reaction scheme provides for the decomposition of tert-butyl hydroperoxide intermediates via reaction with PFe-OH complexes; the PFeIII species responsible for hydroperoxide decomposition are regenerated by reaction of PFeII with dioxygen under these experimental conditions.

A pilot study for a randomized controlled trial comparing the efficacy, safety and cost-effectiveness of surgical treatments of the prostate

OBJECTIVE

To assess the numbers of men in outpatients and subsequently undergoing transurethral resection of the prostate (TURP) who were referred during 1993-94 and 1996-97, thereby assessing the feasibility of a subsequent study of treatment efficacy in men with bladder outlet obstruction secondary to benign prostatic hyperplasia, prospectively randomized to the surgical treatment options, i.e. TURP, laser ablation of the prostate, transurethral needle ablation and T3 thermotherapy, to investigate treatment outcome, cost-efficacy and cost-benefit.

PATIENTS AND METHODS

All patients considered and consenting for prostate surgery were reviewed prospectively with a view to inclusion in the proposed trial. The diagnosis was based on two estimates of flow rate from voids of >150 mL and from symptoms assessed using the International Prostate Symptom Score. All patients had TURP explained by a urological surgeon and nursing staff, and subsequently had further consultation with research staff.

RESULTS

Patients seen in clinic as new referrals increased by 11% between the periods assessed, although the numbers undergoing TURP decreased by 19%. Of the 383 patients screened, who were on the waiting list for TURP, only 13 elected to enter the trial. Of the 383 men, 267 (67%) ultimately had prostate surgery, with 39 (10%) electing to continue with watchful waiting and 34 (9%) continuing with pharmacotherapy.

CONCLUSION

Although more men with benign prostatic disease and lower urinary tract symptoms are being seen in clinics, the reduced proportion of patients continuing to surgical intervention will lead to increasing difficulty in carrying out randomized controlled clinical trials assessing surgical options. With ever more therapeutic options available, patients find it difficult to make decisions in both the clinical situation and when asked to enter a trial. Fully informed decisions by both the surgeon and the patient will only be possible when objective data are available from trials that investigate outcome, cost-efficacy and cost-benefit. This study suggests that when presented with more information and counselling, fewer men decide to undergo prostate surgery for symptomatic BPH.

Understanding Interphase Boundary Dynamics by In Situ High-Resolution and Energy-Filtering Transmission Electron Microscopy and Real-Time Image Simulation

: This study discusses the use of in situ high-resolution transmission electron microscropy (HRTEM) techniques to determine the structure, composition, and interphase boundary dynamics during phase transformations at the atomic level. Three main in situ HRTEM techniques are described: (1) in situ HRTEM dynamic studies that are performed on the same precipitate plates from different viewing directions to determine the three-dimensional structure of the interfaces; (2) in situ compositional mapping of precipitate interfaces obtained by energy-filtering TEM experiments at temperature in a HRTEM, and (3) real-time HRTEM image simulations that are being created for comparison with and interpretation of experimental in situ HRTEM dynamic observations. The results from these studies demonstrate that it is possible to understand the mechanisms and kinetics of interphase boundary motion at the atomic level.

A prospective audit of the use of a prostate clinic

OBJECTIVE

To assess the efficiency of a prostate clinic and to determine the treatment outcomes and the proportion of patients who could potentially be managed by their General Practitioners (GPs).

PATIENTS AND METHODS

Referral letters from GPs were screened by the consultant urologists and appropriate patients seen in the next available prostate clinic. The initial assessment consisted of an International Prostate Symptom Score and a medical history, uroflowmetry, ultrasonographically determined post-void urine volumes, renal function tests and measurement of prostate specific antigen, in addition to a physical examination and a digital rectal examination. Further investigations were requested as required.

RESULTS

Over a period of 18 months, 403 patients were seen, 90% of them within 12 weeks from the time of referral. Uroflowmetry was performed in 96% of patients and further urodynamics in 22%. Bladder outlet obstruction was diagnosed in 246 (61%) patients and primary detrusor instability was detected in 20 (5%) patients. Fourteen per cent of patients were returned to the care of the GP following their first visit. The audit identified a potential group of patients (52%) who could be managed by their GP. Seven per cent underwent prostate surgery for the relief of bladder outlet obstruction.

CONCLUSION

The prostate clinic significantly reduced the delay for patients to be seen at the hospital and facilitated rapid assessment and investigation, much of which was carried out by a nurse practitioner during the first visit (in most cases). Several patients were identified who could be managed in the community.

Impotence in diabetes: aetiology, implications for treatment and preferred vacuum device

In an assessment of the contributions of autonomic neuropathy and vascular disease to the aetiology of male impotence in diabetes, evidence of autonomic neuropathy was identified in 23/39 (59%) individuals complaining of impotence. Thirteen of 26 men aged < 60 years tested with an intracorporeal injection of papaverine experienced little or no response and seven had tumescence but no rigidity. Radioisotope phallography demonstrated vascular disease in six of these seven, suggesting evidence of a vascular component in 19/26 (73%). Only one patient had non-organic impotence. Overall, evidence of vascular disease alone was demonstrated in 10/26 (38%), vascular disease plus autonomic neuropathy in 9/26 (35%), and autonomic neuropathy alone in 6/26 (23%). Many diabetic men complaining of impotence appear to have a significant vascular component which renders intracorporeal papaverine treatment ineffective. We compared the performance of a vacuum constriction-band (Erecaid) and condom-type (Synergist) device in 10 randomly selected men from this group. The devices, provided in random order for 5 months each, were assessed by questionnaire and interview of both the patient and partner. Two couples defaulted and another could use neither device. Although erectile capacity could be restored in the remainder, subsequent intercourse was only deemed satisfactory to both partners in five couples, who unanimously preferred the constriction-band device. In treatment with vacuum devices the constriction-band type seems to be the device of choice; the condom type should probably be reserved for those unable to use the constriction-band type.

Measurement of prostate-specific antigen and prostatic acid phosphatase concentrations in serum before and 1-42 days after transurethral resection of the prostate and orchidectomy

Preoperative intra-individual variation for determinations of prostate-specific antigen and prostatic acid phosphatase concentrations, 15-30% in 92 patients with benign prostatic hyperplasia, limits the diagnostic usefulness of both tumor markers. In benign prostatic hyperplasia (214 patients), concentrations of these tumor markers increased in the initial postoperative period. Prostatic acid phosphatase concentration then decreased by the third postoperative day. Prostate-specific antigen concentration remained above normal in the first postoperative week but had decreased by 42 days. In prostatic carcinoma (46 patients), the concentrations of these tumor markers did not increase postoperatively. During the first week, the concentrations of prostatic acid phosphatase began to fall, but prostate-specific antigen showed a decrease only at 42 days. After orchidectomy (11 patients), the concentrations of both markers had decreased by five days. Concentrations of prostate-specific antigen but not of prostatic acid phosphatase were significantly increased in patients with metastases at 42 days postoperatively. When the concentration of tumor marker did decrease, the magnitude of change was greater for prostatic acid phosphatase than for prostate-specific antigen. These changes were accentuated after an orchidectomy.

Systemic mannitol increases retinal adhesiveness measured in vitro

Pigmented rabbits were given mannitol intravenously, and at various times thereafter blood osmolality was measured and eyes were enucleated to measure retinal adhesiveness to the retinal pigment epithelium. Both blood osmolality and retinal adhesion increased in proportion to the dose of mannitol. We found a measurable increase in retinal adhesion as early as 10 minutes and as late as 4 hours after mannitol injection. We suspect that mannitol dehydrates the subretinal space and thereby enhances the adhesive properties of the interphotoreceptor matrix or tightens the interdigitation between photoreceptors and pigment epithelial cells. Our data suggest that mannitol could have clinical application in the management of retinal detachments.

The treatment of perforated duodenal ulcer

The prognosis of 189 patients with a perforated duodenal ulcer was analysed. There were three treatment groups, non-operative, simple closure and definitive ulcer surgery. The prognosis of the patients was analysed in terms of the chronicity of the ulcer. Perforations occurring in acute duodenal ulcers have an excellent prognosis, with similar results in each group in this series. All perforations of chronic duodenal ulcers should be treated by emergency surgery.

Canine small bowel transplantation. A study of the immunological responses

A canine small bowel allograft model was used to determine the effects of radiation to the graft in modifying the immunological effects of the passenger leukocytes. When untreated allografts were transplanted, death of the recipient animals occurred at a mean of nine days. The allograft was well-preserved and showed no signs of rejection. The reasons for attributing death to graft-versus-host (GVH) disease are discussed. When allografts were treated with 150 rads prior to transplantation, allograft rejection occurred, with death of the recipient animals at a mean of 9.2 days. This was the only group in which cell-mediated immunity developed. When allografts were treated with 50 rads, prolonged survival of the recipients to a mean of 28 days was noted. It is postulated that in this group a balance was struck between the allograft rejection reaction and GVH disease, with prolongation of allograft survival.