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Isoniazid toxicity from self-poisoning or dosing errors remains common in regions of the world where tuberculosis is prevalent. Although the treatment of isoniazid poisoning is centered on supportive care and pyridoxine administration, extracorporeal treatments (ECTRs), such as hemodialysis, have been advocated to enhance elimination of isoniazid. No systematic reviews or evidence-based recommendations currently exist on the benefit of ECTRs for isoniazid poisoning. The Extracorporeal Treatments in Poisoning (EXTRIP) workgroup systematically collected and rated the available evidence on the effect of and indications for ECTRs in cases of isoniazid poisoning. We conducted a systematic review of the literature, screened studies, extracted data on study characteristics, outcomes, and measurement characteristics, summarized findings, and formulated recommendations following published EXTRIP methods. Forty-three studies (two animal studies, 34 patient reports or patient series, and seven pharmacokinetic studies) met inclusion criteria. Toxicokinetic or pharmacokinetic analysis was available for 60 patients, most treated with hemodialysis (n = 38). The workgroup assessed isoniazid as "Moderately Dialyzable" by hemodialysis for patients with normal kidney function (quality of evidence = C) and "Dialyzable" by hemodialysis for patients with impaired kidney function (quality of evidence = A). Clinical data for ECTR in isoniazid poisoning were available for 40 patients. Mortality of the cohort was 12.5%. Historical controls who received modern standard care including appropriately dosed pyridoxine generally had excellent outcomes. No benefit could be extrapolated from ECTR, although there was evidence of added costs and harms related to the double lumen catheter insertion, the extracorporeal procedure itself, and the extracorporeal removal of pyridoxine. The EXTRIP workgroup suggests against performing ECTR in addition to standard care (weak recommendation, very low quality of evidence) in patients with isoniazid poisoning. If standard dose pyridoxine cannot be administered, we suggest performing ECTR only in patients with seizures refractory to GABAA receptor agonists (weak recommendation, very low quality of evidence).

Introduction The chronic recreational inhalation of nitrous oxide (N2 O) "nanging", can have adverse neurological and psychiatric effects. This study evaluated cases of N2 O abuse presenting to two hospitals, N2 O-related deaths, and N2 O-related internet and social media trends. Methods Retrospective review of two toxicology units, from July 2017-Oct 2020, of patients presenting with chronic N2 O use and neurological and/or psychiatric symptoms. We evaluated 10 y (2010-2019) of internet search and social media trends involving N2 O, and the National Coronial Information System (NCIS) database for deaths across Australia. Results Twenty-two patients were identified: median age 22 y, half female, 17 Asian background and 15 students. Presentations included decreased mobility or unsteady gait (n = 15) and psychiatric symptoms (n = 5). The median reported bulb use/day was 300 (IQR:200-370), for a median of 6 months (IQR:3-24). On MRI 10/18 had subacute combined degeneration of the spinal cord and 7/7 sensorimotor neuropathy on nerve conduction studies. All received high-dose intramuscular vitamin B12 and 11 methionine. Despite prolonged rehabilitation, nine required walking aids on discharge. Since 2017 social media posts and internet searches for N2 O increased rapidly, the latter mostly directed at obtaining N2 O canisters. From the NCIS, 36 deaths were identified, 12 unintentional (recreational drug-use), 20 intentional self-harm and 4 traumatic. Conclusion We report a case series of symptomatic chronic N2 O use, many with ongoing neurological sequelae. Furthermore, a sharp increase in internet searches to obtain N2 O cannisters was noted. Education of high-risk student groups on the long-term sequalae is important. This article is protected by copyright. All rights reserved.

Backgroundβ-adrenergic antagonists (BAAs) are used to treat cardiovascular disease such as ischemic heart disease, congestive heart failure, dysrhythmias, and hypertension. Poisoning from BAAs can lead to severe morbidity and mortality. We aimed to determine the utility of extracorporeal treatments (ECTRs) in BAAs poisoning.MethodsWe conducted systematic reviews of the literature, screened studies, extracted data, and summarized findings following published EXTRIP methods.ResultsA total of 76 studies (4 in vitro and 2 animal experiments, 1 pharmacokinetic simulation study, 37 pharmacokinetic studies on patients with end-stage kidney disease, and 32 case reports or case series) met inclusion criteria. Toxicokinetic or pharmacokinetic data were available on 334 patients (including 73 for atenolol, 54 for propranolol, and 17 for sotalol). For intermittent hemodialysis, atenolol, nadolol, practolol, and sotalol were assessed as dialyzable; acebutolol, bisoprolol, and metipranolol were assessed as moderately dialyzable; metoprolol and talinolol were considered slightly dialyzable; and betaxolol, carvedilol, labetalol, mepindolol, propranolol, and timolol were considered not dialyzable. Data were available for clinical analysis on 37 BAA poisoned patients (including 9 patients for atenolol, 9 for propranolol, and 9 for sotalol), and no reliable comparison between the ECTR cohort and historical controls treated with standard care alone could be performed. The EXTRIP workgroup recommends against using ECTR for patients severely poisoned with propranolol (strong recommendation, very low quality evidence). The workgroup offered no recommendation for ECTR in patients severely poisoned with atenolol or sotalol because of apparent balance of risks and benefits, except for impaired kidney function in which ECTR is suggested (weak recommendation, very low quality of evidence). Indications for ECTR in patients with impaired kidney function include refractory bradycardia and hypotension for atenolol or sotalol poisoning, and recurrent torsade de pointes for sotalol. Although other BAAs were considered dialyzable, clinical data were too limited to develop recommendations.ConclusionsBAAs have different properties affecting their removal by ECTR. The EXTRIP workgroup assessed propranolol as non-dialyzable. Atenolol and sotalol were assessed as dialyzable in patients with kidney impairment, and the workgroup suggests ECTR in patients severely poisoned with these drugs when aforementioned indications are present.

Background Intentional poisoning with warfarin is not the same as over-anticoagulation, for which guidelines exist. The coagulopathy resulting from a warfarin overdose is reversed with vitamin K 1 , the dose and timing of which is often guided by experience with the management of over-anticoagulation with warfarin therapy, rather than acute overdose. Case Report We report a case of a 50-year-old man who ingested an unknown amount of his warfarin, venlafaxine, and paracetamol. He presented with an international normalized ratio (INR) of 2.5, which steadily increased over 24 h to 7, despite receiving an initial 1 mg of vitamin K 1 . He was then treated with 5 mg vitamin K 1 , and once the INR returned to 4.5, 40 h post ingestion, he was discharged home. He was also treated with a full course of acetylcysteine for the paracetamol overdose. The following day his INR rebounded to 8.5 and he suffered a spontaneous epistaxis requiring readmission; he was treated with low titrated doses of vitamin K 1 . The warfarin concentration was 74.6 μg/mL 26 h post ingestion and decreased to 3.7 μg/mL over 72 h. Why Should an Emergency Physician Be Aware of This? Our case highlights the risk of a rebound elevated INR even 3 days after acute warfarin overdose despite treatment with vitamin K 1 . Understanding the pharmacokinetics of vitamin K 1 in comparison with warfarin, repeat INR testing, and continued treatment with oral vitamin K 1 may help avoid complications of rebound coagulopathy in warfarin overdose.

CASE REPORT: We report a fatal case of a 37 year old gentleman who ingested a MCPA/bromoxynil co-formulation herbicide. Although clinically well on initial examination, our patient declined dramatically over his 18 h admission with increasing CO2 production, hyperthermia and metabolic derangement to eventually die from cardiac asystole 20 h post ingestion. Two hours after ingestion the MCPA concentration was 83.9 μg/mL and bromoxynil concentration was 137 μg/mL. DISCUSSION: The patients' mechanism of death appeared to be uncoupling of oxidative phosphorylation, excess CO2 production and hyperthermia. There is limited knowledge on the acute toxicity of these herbicides, in particular bromoxynil, and this case highlights the relentless progression of severe toxicity in humans. The collaboration was supported by an NHMRC Program Grant (1055176). Geoff Isbister is supported by an NHMRC Senior Research Fellowship ID 1061041 and Mike Roberts is supported by an NHMRC Senior Principal Research Fellowship ID 1002611.

CONTEXT. Toxicity from recreational substances marketed for other purposes is a well-documented clinical entity. We present two cases of phenibut toxicity procured via the internet. Case Details. A 20-year-old female presented to the emergency department (ED) having used phenibut the prior day. The main finding was a decreased level of consciousness, however when roused she became delirious. Supportive care only was required with no specific intervention. The patient made a full recovery over a 24-hour period and admitted to use of phenibut purchased online. Plasma phenibut concentration was 29.7 μg/ml. A 38-year-old male presented to ED with an agitated delirium. The prior evening he had used tetrahydrocannabinol or THC, alcohol and phenibut, the latter purchased via the internet. His behavioural state had a suboptimal response to parenteral sedation. He was subsequently intubated for airway protection in the context of ongoing sedation to optimally manage his behavioural state. Post extubation the next morning he admitted using phenibut. Plasma phenibut concentration was 36.5 μg/ml. Discussion. Altered mental status was the predominant manifestation of phenibut toxicity in these cases. Clinicians to be aware of how phenibut toxicity may present as the internet has widened access to such substances. Refereed/Peer-reviewed