A mechanistic investigation of thrombotic microangiopathy associated with IV abuse of Opana ER

In vitro test methods for evaluating high molecular weight polyethylene oxide polymer induced hemolytic and thrombotic potential

To combat opioid abuse, the U.S. Food and Drug Administration (FDA) released a comprehensive action plan to address opioid addiction, abuse, and overdose that included increasing the prevalence of abuse-deterrent formulations (ADFs) in opioid tablets. Polyethylene oxide (PEO) has been widely used as an excipient to deter abuse via nasal insufflation. However, changes in abuse patterns have led to unexpected shifts in abuse from the nasal route to intravenous injection. Case reports identify adverse effects similar to thrombotic thrombocytopenic purpura (TTP) syndrome following the intravenous (IV) abuse of opioids containing PEO excipient. Increased risk of IV opioid ADF abuse compared to clinical benefit of the drug led to the removal of one opioid product from the market in 2017. Because many generic drugs containing PEO are still in development, there is interest in assessing safety consistent with generic drug regulation and unintended uses. Currently, there are no guidelines or in vitro assessment tools to characterize the safety of PEO excipients taken via intravenous injection. To create a more robust excipient safety evaluation tool and to study the mechanistic basis of HMW PEO-induced TMA, a dynamic in vitro test system involving blood flow through a needle model has been developed.

Asymmetrical Flow Field Flow Fractionation for Molar Mass Characterization of Polyethylene Oxide in Abuse-Deterrent Formulations

High molar mass polyethylene oxide (HM-PEO) is commonly used to enhance the mechanical strength of solid oral opioid drug products to deter abuse. Because the properties of PEO depend on molar mass distribution, accurately determining the molar mass distribution is a necessary part of understanding PEO's role in abuse-deterrent formulations (ADF). In this study, an asymmetrical flow field-flow fractionation (AF4) analytical procedure was developed to characterize PEO polymers with nominal molar masses of 1, 4 or 7 MDa as well as those from in-house prepared placebo ADF. The placebo ADF were manufactured using direct compress or hot-melt-extrusion methods, and subjected to physical manipulation, such as heating and grinding before measurement by AF4 were performed. The molar mass distribution characterized by AF4 revealed that PEO was sensitive to thermal stress, exhibiting decreased molar mass with increased heat exposure. The optimized AF4 method was deemed suitable for characterizing HM-PEO, offering adequate dynamic separation range for PEO with molar mass from 100 kDa to approximately 10 MDa.

Emerging Insights into Glomerular Vascular Pole and Microcirculation

The glomerular vascular pole is the gate for the afferent and efferent arterioles and mesangial cells and a frequent location of peripolar cells with an unclear function. It has been studied in definitive detail for >30 years, and functionally interrogated in the context of signal transduction from the macula densa to the mesangial cells and afferent arteriolar smooth muscle cells from 10 to 20 years ago. Two recent discoveries shed additional light on the vascular pole, with possibly far-reaching implications. One, which uses novel serial section electron microscopy, reveals a shorter capillary pathway between the basins of the afferent and efferent arterioles. Such a pathway, when patent, may short-circuit the multitude of capillaries in the glomerular tuft. Notably, this shorter capillary route is enclosed within the glomerular mesangium. The second study used anti-Thy1.1-induced mesangiolysis and intravital microscopy to unequivocally establish in vivo the long-suspected contractile function of mesangial cells, which have the ability to change the geometry and curvature of glomerular capillaries. These studies led me to hypothesize the existence of a glomerular perfusion rheostat, in which the shorter path periodically fluctuates between being more and less patent. This action reduces or increases blood flow through the entire glomerular capillary tuft. A corollary is that the GFR is a net product of balance between the states of capillary perfusion, and that deviations from the balanced state would increase or decrease GFR. Taken together, these studies may pave the way to a more profound understanding of glomerular microcirculation under basal conditions and in progression of glomerulopathies.

Functional properties of thermally tampered poly(ethylene oxide)

Introduction: Poly(ethylene oxide) (PEO) is the most common polymer used in commercial abuse-deterrent tablets. Due to its vulnerability to high-temperature manipulation, we investigated abuse-deterrent capability and the toxicity of this polymer upon thermal treatments at 80°C and 180°C for 1 hour. Methods: Tablets (200 mg PEO and 300 mg Avicel®) were directly compressed under 2000 lb. The thermally manipulated PEOs were evaluated for their viscosity, crushability, structural changes, and cell toxicity. Results: Our findings showed that 180°C-treated tablets underwent some degrees of oxidative degradation with profound toxicity in both mesenchymal stem cells and MG63 cells. The 180°C-treated tablets exhibited almost no resistance against crushing and were prone to abuse. While thermal processing of PEO at around its melting temperature is a common approach to enhance crush resistance of its dosage forms, thermal manipulation at close to the PEO's oxidation temperature can lead to structural changes, dramatic loss of crush and extraction resistance, and significant cell toxicity. Conclusion: Similar to the low molecular weight PEO, when thermally manipulated at its thermo-oxidative temperature, the high molecular weight PEO loses its deterrence performance and causes severe cell toxicity.

Relative potency of intravenous oxymorphone compared to other µ opioid agonists in humans - pilot study outcomes

AIMS

Intravenous (IV) misuse of the µ opioid analgesic oxymorphone has caused significant public health harms; however, no controlled data on its IV abuse potential are available. The primary aims of this pilot study were to directly compare IV oxymorphone to IV oxycodone, morphine, and hydromorphone on a subjective measure of drug liking and to assess relative potency.

METHODS

Participants (n = 6) with opioid use disorder, physical dependence, and current IV use completed this two-site, within-subject, double-blind, placebo-controlled, inpatient pilot study. During each session, one IV dose (mg/70 kg) was administered: oxymorphone (1.8, 3.2, 5.6, 10, 18, 32), hydromorphone (1.8, 3.2, 5.6, 10, 18), oxycodone (18, 32, 56), morphine (18, 32), and placebo. Data were collected before and for 6 h after dosing. Primary outcomes included safety/physiological effects, subjective reports of drug liking, and relative potency estimates.

RESULTS

All active test drugs produced prototypical, dose-related µ opioid agonist effects (e.g., miosis). Oxymorphone was more potent than the comparator opioids on several measures, including drug liking and respiratory depression (p < 0.05). Across abuse-related subjective outcomes, oxymorphone was 2.3-2.8-fold more potent than hydromorphone and 12.5-14-fold more potent than oxycodone (p < 0.05).

CONCLUSIONS

Despite the relatively small sample size, this pilot study detected robust oxymorphone effects. Oxymorphone was far more potent than the comparator opioids, particularly on abuse potential outcomes. Overall, these findings may help explain surveillance reports that demonstrate, after adjusting for prescription availability, oxymorphone is injected at the highest frequency, relative to other prescription opioids.

Polyethylene Oxide Molecular Size Determines the Severity of Atypical Thrombotic Microangiopathy in a Guinea Pig Model of Acute Intravenous Exposure

In 2017, Opana ER was voluntarily removed from the U.S. market based on concerns that its risks outweighed its therapeutic benefits. The data that supported this conclusion were based on postmarketing evaluation that demonstrated increased intravenous abuse associated outbreaks of HIV, hepatitis C, and uniquely, a thrombotic thrombocytopenic purpura (TTP)-like syndrome. In 2017, the cause was mechanistically linked to intravenous exposure of the high-molecular weight polyethylene oxide (PEO), an excipient component of the drug product. However, it was unknown how differing PEO preparations might alter this response in vivo. Knowing the likelihood of a PEO driven atypical thrombotic microangiopathy with hemolytic uremic syndrome (TMA-HUS), this study was specifically designed with the primary objective focused on understanding the impact of PEO molecular weight on TMA-HUS in a guinea pig model of acute repeat PEO (1, 4, and 7 MDa) dosing. Results from this analysis suggest that repeated dosing with PEO 4 and 7 MDa, but not 1 MDa induced a marked intravascular hemolysis with schistocytes, mild anemia, thrombocytopenia, hemoglobinuria, and kidney injury, consistent with observations of a TMA-HUS-like syndrome. Nonetheless, observations of tissue microthrombi, complement or altered von Willebrand factor involvement were not observed, which would be consistent with a definitive TMA. Further, only 7 MDa PEO dosing was associated with marked renal hypoxia. Taken together, this study defines renal injury risk with PEO formulations >1 MDa that is driven by a robust intravascular hemolysis and potentially, tissue hypoxia.

Complement in Secondary Thrombotic Microangiopathy

Thrombotic microangiopathy (TMA) is a condition characterized by thrombocytopenia and microangiopathic hemolytic anemia (MAHA) with varying degrees of organ damage in the setting of normal international normalized ratio and activated partial thromboplastin time. Complement has been implicated in the etiology of TMA, which are classified as primary TMA when genetic and acquired defects in complement proteins are the primary drivers of TMA (complement-mediated TMA or atypical hemolytic uremic syndrome, aHUS) or secondary TMA, when complement activation occurs in the context of other disease processes, such as infection, malignant hypertension, autoimmune disease, malignancy, transplantation, pregnancy, and drugs. It is important to recognize that this classification is not absolute because genetic variants in complement genes have been identified in patients with secondary TMA, and distinguishing complement/genetic-mediated TMA from secondary causes of TMA can be challenging and lead to potentially harmful delays in treatment. In this review, we focus on data supporting the involvement of complement in aHUS and in secondary forms of TMA associated with malignant hypertension, drugs, autoimmune diseases, pregnancy, and infections. In aHUS, genetic variants in complement genes are found in up to 60% of patients, whereas in the secondary forms, the finding of genetic defects is variable, ranging from almost 60% in TMA associated with malignant hypertension to less than 10% in drug-induced TMA. On the basis of these findings, a new approach to management of TMA is proposed.

Anesthetic and Analgesic Drug Products Advisory Committee Activity and Decisions in the Opioid-crisis Era

The United States Food and Drug Administration is tasked with ensuring the efficacy and safety of medications marketed in the United States. One of their primary responsibilities is to approve the entry of new drugs into the marketplace, based on the drug’s perceived benefit–risk relationship. The Anesthetic and Analgesic Drug Product Advisory Committee is composed of experts in anesthesiology, pain management, and biostatistics, as well as consumer and industry representatives, who meet several times annually to review new anesthetic-related drugs, those seeking new indications, and nearly every opioid-related application for approval. The following report describes noteworthy activities of this committee since 2017, as it has grappled, along with the Food and Drug Administration, to balance the benefit–risk relationships for individual patients along with the overarching public health implications of bringing additional opioids to market. All anesthesia advisory committee meetings since 2017 will be described, and six will be highlighted, each with representative considerations for potential new opioid formulations or local anesthetics.

Haptoglobin Therapeutics and Compartmentalization of Cell-Free Hemoglobin Toxicity

Hemolysis and accumulation of cell-free hemoglobin (Hb) in the circulation or in confined tissue compartments such as the subarachnoid space is an important driver of disease. Haptoglobin is the Hb binding and clearance protein in human plasma and an efficient antagonist of Hb toxicity resulting from physiological red blood cell turnover. However, endogenous concentrations of haptoglobin are insufficient to provide protection against Hb-driven disease processes in conditions such as sickle cell anemia, sepsis, transfusion reactions, medical-device associated hemolysis, or after a subarachnoid hemorrhage. As a result, there is increasing interest in developing haptoglobin therapeutics to target 'toxic' cell-free Hb exposures. Here, we discuss key concepts of Hb toxicity and provide a perspective on the use of haptoglobin as a therapeutic protein.

Ferroportin inhibition attenuates plasma iron, oxidant stress, and renal injury following red blood cell transfusion in guinea pigs

BACKGROUND

Red blood cell (RBC) transfusions result in the sequestration and metabolism of storage-damaged RBCs within the spleen and liver. These events are followed by increased plasma iron concentrations that can contribute to oxidant stress and cellular injury. We hypothesized that administration of a ferroportin inhibitor (FPN-INH) immediately after acute RBC exchange transfusion could attenuate posttransfusion circulatory compartment iron exposure, by retaining iron in spleen and hepatic macrophages.

STUDY DESIGN AND METHODS

Donor guinea pig blood was leukoreduced, and RBCs were preserved at 4°C. Recipient guinea pigs (n = 5/group) were exchange transfused with donor RBCs after refrigerator preservation and dosed intravenously with a small-molecule FPN-INH. Groups included transfusion with vehicle (saline), 5 mg/kg or 25 mg/kg FPN-INH. A time course of RBC morphology, plasma non-transferrin-bound iron (NTBI) and plasma hemoglobin (Hb) were evaluated. End-study spleen, liver, and kidney organ iron levels, as well as renal tissue oxidation and injury, were measured acutely (24-hr after transfusion).

RESULTS

RBC transfusion increased plasma NTBI, with maximal concentrations occurring 8 hours after transfusion. Posttransfusion iron accumulation resulted in tubule oxidation and acute kidney injury. FPN inhibition increased spleen and liver parenchymal/macrophage iron accumulation, but attenuated plasma NTBI, and subsequent renal tissue oxidation/injury.

CONCLUSION

In situations of acute RBC transfusion, minimizing circulatory NTBI exposure by FPN inhibition may attenuate organ-specific adverse consequences of iron exposure.

Diagnostic Testing for Differential Diagnosis in Thrombotic Microangiopathies

Thrombotic microangiopathies (TMAs) are multiple disease entities with different etiopathogeneses, characterized by thrombocytopenia, microangiopathic hemolytic anemia (MAHA) with schistocytosis, variable symptoms including fever, and multi-organ failure such as mild renal impairment and neurological deficits. The two paradigms of TMAs are represented on one hand by acquired thrombotic thrombocytopenic purpura (TTP) and on the other by hemolytic uremic syndrome (HUS). The differential diagnosis between these two paradigmatic forms of TMA is based on the presence of either frank renal failure in HUS or a severe deficiency (<10%) of the zinc-protease ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13) in TTP. ADAMTS13 is an enzyme involved in the proteolytic processing of von Willebrand factor (vWF), and its deficiency results in formation of high-molecular-weight vWF-rich microthrombi in the environment of the microvasculature. The presence of these ultra-large vWF multimers in the microcirculation can recruit platelets, promoting multi-organ ischemic lesions. The presence of ADAMTS13 activity at >10% could rule out the presence of a TTP form. However, it is often difficult to differentiate either a TTP or HUS clinical scenario presenting with typical symptoms of TMA. There are in fact several additional diagnoses that should be considered in patients with ADAMTS13 activity of >10%. Widespread inflammation with endothelial damage and adverse reactions to drugs play a central role in the pathogenesis of several forms of TMA, and in these cases, the differential diagnosis should be directed at the underlying disease. Hence, a correct etiologic diagnosis of TMA should involve a critical illness, cancer-associated TMA, drug-induced TMA, and hematopoietic transplant-associated TMA. A complete assessment of all the possible etiologies for TMA symptoms, including acquired or congenital TTP, will allow for a more accurate diagnosis and application of a more appropriate treatment.

Mitigation of IV Abuse Through the Use of Abuse-Deterrent Opioid Formulations: An Overview of Current Technologies

Providers who treat patients with chronic pain face a dual challenge: providing adequate access to opioid therapies for appropriate pain management while adopting strategies to minimize the risk for abuse. Commonly prescribed opioids have substantial abuse potential when administered intravenously, and extended‐release (ER)/long‐acting (LA) opioids may be targeted for intravenous (IV) abuse because of the higher per‐dose medication level. The consequences of IV opioid abuse are severe and increase the risks for adverse outcomes, including mortality due to acute health events, serious infections, and deep vein thrombosis, to name a few. To reduce the potential for abuse of prescription opioids by both recreational and experienced drug abusers, abuse‐deterrent formulations (ADFs) of opioid medications employ either physical/chemical barriers or agonist‐antagonist combinations. Here we review the development and use of opioid ADFs as a harm‐reduction strategy, and their potential for mitigating IV opioid abuse. The approved ER/LA opioids with ADF labeling in the United States include formulations of oxycodone, hydrocodone, and morphine. Findings from in vitro laboratory tests of abuse deterrence for opioid ADFs are described herein, as are data from human abuse potential studies for IV abuse of those ADF products, for which such studies are feasible (ie, abuse‐deterrent agonist‐antagonist formulations). The available ADF opioids may decrease both the attractiveness and the feasibility of IV abuse. The adoption of ADF opioids represents one tactic for providing access to needed medication for patients with chronic pain, while potentially reducing the risk for opioid abuse, in a comprehensive effort to combat the opioid epidemic.

Bilateral exudative retinal detachments due to thrombotic microangiopathy associated with intravenous abuse of Opana ER

Purpose

To report the only known case, to our knowledge, of bilateral exudative retinal detachments in the setting of thrombotic microangiopathy associated with intravenous abuse of extended-release oxymorphone (Opana ER).

Observations

A 35-year-old male presented with headaches and acute, painless vision loss in the context of daily IV abuse of crushed oral Opana ER. The patient was found to have microangiopathic hemolytic anemia (MAHA), acute kidney injury in conjunction with hypertensive crisis and bilateral exudative retinal detachments.

Conclusions and importance

Bilateral exudative retinal detachments are rare ophthalmic complications that have been reported with thrombotic thrombocytopenic purpura (TTP). Non-TTP thrombotic microangiopathy, initially described as a “TTP-like illness” consisting of MAHA and thrombocytopenia, has been associated with the IV abuse of Opana ER. We report a case of bilateral exudative retinal detachments due to thrombotic microangiopathy in the setting of IV abuse of Opana ER.

Abuse-deterrent Opioid Formulations

Abuse-deterrent opioid formulations have been suggested as one way to decrease the abuse, addiction, and overdose of orally prescribed opioids. Ten oral opioid formulations have received abuse-deterrent labeling by the U.S. Food and Drug Administration (FDA). Their properties consist of physical and/or chemical means by which the pills resist manipulation and create a barrier to unintended administration, such as chewing, nasal snorting, smoking, and intravenous injection. In this review, we describe the mechanisms of abuse-deterrent technology, the types of premarketing studies required for FDA approval, the pharmacology of the currently approved abuse-deterrent opioid formulations, and the evidence for and against their influence on opioid abuse. We conclude that there is currently insufficient evidence to indicate that the availability of abuse-deterrent opioid formulations has altered the trajectory of opioid overdose and addiction; however, postmarketing studies are in their infancy, and novel deterrent formulations are continually being developed and submitted for marketing approval.

Thrombocytopenia in hospitalized patients: approach to the patient with thrombotic microangiopathy

Thrombotic microangiopathies (TMAs), specifically, thrombotic thrombocytopenic purpura (TTP) and complement-mediated hemolytic uremic syndrome (CM-HUS) are acute life-threatening disorders that require prompt consideration, diagnosis, and treatment to improve the high inherent mortality and morbidity. Presentation is with microangiopathic hemolytic anemia and thrombocytopenia (MAHAT) and variable organ symptoms resulting from microvascular thrombi. Neurological and cardiac involvement is most common in TTP and associated with poorer prognosis and primarily renal involvement in CM-HUS. TTP is confirmed by severe ADAMTS13 deficiency (which can be undertaken in real time) and CM-HUS by an abnormality in complement regulators, confirmed by mutational analysis (in 60% to 70% of cases) or the presence of Factor H antibodies (which may not be available for weeks or months). Plasma exchange (PEX) should be started as soon as possible following consideration of these TMAs. Differentiation of the diagnosis requires specific treatment pathways thereafter (immunosuppression primarily for TTP and complement inhibitor therapy for CM-HUS). As the diagnosis is based on MAHAT, there are a number of other medical situations that need to be excluded and these are discussed within the article. Other differentials presenting as TMAs may also be associated with micro- or macrovascular thrombosis, yet are more likely to be due to direct endothelial damage, many of which do not have a clear therapeutic benefit with PEX.

Thrombotic microangiopathy associated with intravenous injection of extended-release oxycodone

We describe the case of a 35-year-old man presenting with thrombotic microangiopathy (TMA) and renal impairment following, as he later disclosed, intravenous injection of oral formulation tamper-resistant extended-release oxycodone hydrochloride (Oxycontin). Recurrent misuse of this agent was associated with relapsing TMA despite treatment with terminal complement inhibitor eculizumab. Cases of TMA have been reported in the USA in association with intravenous misuse of extended-release oxymorphone (Opana ER) after the introduction of a new non-crushable formulation in 2012. There are two reported accounts of TMA associated with tamper-resistant Oxycontin, which became available in Australia in 2014. This is the first documented case in which eculizumab was used. This case illustrates the practical diagnostic challenges in identifying TMA disorders, and the importance of a detailed drug history. It also highlights the need to clarify what role, if any, eculizumab therapy has in cases of drug-associated TMA.

Thrombotic Microangiopathy Secondary to Intravenous Abuse of Opana® ER

Opana ER (oxymorphone) is an opioid drug available throughout the United States, and intravenous abuse of the crushed oral formulation has been associated with drug-induced thrombotic microangiopathy. In this abstract, we describe two young patients who lived together and used Opana ER intravenously. Both presented with microangiopathic hemolytic anemia that mimicked thrombotic thrombocytopenic purpura (TTP). Treating this condition poses a clinical challenge, as it is difficult to distinguish it from TTP. The role for plasma exchange is not clear but can be used while awaiting the results of the ADAMTS-13 activity, but ultimately supportive care with drug discontinuation is the recommended therapy of choice. Patients should be counseled against Opana ER's intravenous use, and users should be offered drug rehabilitation therapy.