Treatment of a potentially lethal dose isoniazid ingestion

Extracorporeal treatments for isoniazid poisoning: Systematic review and recommendations from the EXTRIP workgroup

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 GABA_A receptor agonists (weak recommendation, very low quality of evidence).

Isoniazid toxicosis in dogs: 137 cases (2004-2014)

OBJECTIVE To establish the minimum toxic dose of isoniazid in dogs, characterize the clinical signs and outcomes for dogs following isoniazid ingestion, and determine whether IV administration of pyridoxine to dogs with isoniazid toxicosis is protective against death. DESIGN Retrospective case series. ANIMALS 137 dogs with isoniazid toxicosis. PROCEDURES The electronic database of the American Society for the Prevention of Cruelty to Animals Animal Poison Control Center was reviewed from January 2004 through December 2014 to identify dogs with isoniazid toxicosis. For each dog identified, information extracted from the medical record included signalment, estimated dose of isoniazid ingested, clinical signs, treatment, and outcome. Follow-up communication with pet owners or primary care veterinarians was performed when necessary to obtain missing information. RESULTS Clinical signs of isoniazid toxicosis were observed in 134 of 137 (98%) dogs and included seizures (n = 104), CNS signs without seizures (94), and gastrointestinal (41), cardiovascular (19), urogenital (4), and respiratory (1) abnormalities. Of the 87 dogs for which the outcome was available, 61 survived, 18 died, and 8 were euthanized. Probability of survival was positively associated with body weight and IV administration of pyridoxine and negatively associated with dose of isoniazid ingested and presence of seizures. Dogs that received pyridoxine IV were 29 times as likely to survive as dogs that did not receive pyridoxine IV. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated rapid diagnosis of isoniazid toxicosis and prompt treatment of affected dogs with pyridoxine and other supportive care were imperative for achieving a successful outcome.

Antidotes to coumarins, isoniazid, methotrexate and thyroxine, toxins that work via metabolic processes

Some toxins cause their effects by affecting physiological processes that are fundamental to cell function or cause systemic effects as a result of cellular interaction. This review focuses on four examples, coumarin anticoagulants, isoniazid, methotrexate and thyroxine from the context of management of overdose as seen in acute general hospitals. The current basic clinical pharmacology of the toxin, the clinical features in overdose and evidence base for specific antidotes are discussed. The treatment for this group is based on an understanding of the toxic mechanism, but studies to determine the optimum dose of antidote are still required in all these toxins except thyroxine, where treatment dose is based on symptoms resulting from the overdose.

Effects of pyridoxine on the intestinal absorption and pharmacokinetics of isoniazid in rats

Pyridoxine is always simultaneously administered orally with isoniazid for tuberculosis patients in the clinic to prevent or treat the nervous system side effects induced by isoniazid. So the aim of this research was to investigate the effects of pyridoxine on the intestinal absorption and pharmacokinetics of isoniazid. The intestinal absorption of isoniazid with or without pyridoxine was investigated by the rat single-pass intestinal perfusion model in situ, and a high-performance liquid chromatographic method was applied to study the pharmacokinetics of isoniazid with or without pyridoxine. The results suggested that the intestinal apparent permeability (P app) and intestinal absorption rate constant (K a) for isoniazid (30 μg/ml) were decreased by 43.7 and 36.4 %, respectively, by co-perfused pyridoxine (40 μg/ml). In vivo, the effect of pyridoxine on isoniazid pharmacokinetic correlated with the doses of pyridoxine. The blood concentrations of isoniazid at the absorption phase were affected by co-administered pyridoxine, but the AUC and C max of isoniazid were not greatly affected by pyridoxine as expected from the inhibition by pyridoxine of the intestinal absorption of isoniazid, which could be caused by its rapid absorption phase. Therefore, although the intestinal absorption of isoniazid could be significantly inhibited by pyridoxine, the pharmacokinetics of isoniazid oral administration was not greatly affected by the decreased intestinal absorption of isoniazid due to its rapid absorption.

A Prospective Evaluation of the Impact of Initial Glasgow Coma Score on Prehospital Treatment and Transport of Seizure Patients

Hypothesis:

The initial Glasgow Coma Score (GCS) obtained by prehospital personnel on seizure victims is associated with the likelihood of treatment and transport.

Methods:

Prehospital data were collected prospectively for all patients presenting with seizures to a mid-sized emergency medical services system during a five-month period. A total of 419 cases occurred (62.8% male, 37.2% female). Seizure frequency was highest in infants under the age of three years and in adults in their late 20s. A GCS was recorded in 378 cases (90.2%, study group). The GCS was >10 in 304 patients (80.4%) and ≤10 in 74 (19.6%). Patients with GCS≤10 were more likely to receive: oxygen (50.0% vs. 20.1%, p<.0001); IV (35.1% vs. 8.9%, p<.0001); intravenous (IV) medications (16.2% vs. 1.0%, p<.0001); and transport (97.3% vs. 76.3%, p<.0001).

Conclusion:

Seizure patients with a GCS of ≤10 were more likely to receive a variety of prehospital treatments and to be transported than were patients with GCS >10. However, the clinical indicators that were used to make the decision that it was “safe” not to transport nearly one-third of the patients are unclear. Essentially no data exist regarding the parameters impacting treatment and transport of seizure patients. Future investigations with outcome data, are needed to determine whether low risk criteria can be developed to identify those patients (if any) that do not require treatment or transport. A GCS may provide an objective, reproducible parameter upon which to begin formulating such criteria.

Thoracic spine compression fracture during isoniazid-induced seizures: case report

We report here an 11-year-old previously healthy girl with isoniazid intoxication who sustained a seizure-induced thoracic compression fracture. The following might be the first such case reported in the medical literature. Isoniazid toxicity should be suspected in any patient who comes to the emergency department with refractory seizures and metabolic acidosis. Forceful muscle contractions during a convulsive seizure can result in vertebral compression fracture, especially in the midthoracic region. A complaint of back pain after isoniazid-induced seizures in patients raises a strong suspicion of vertebral fracture and should be evaluated radiologically.

Coma caused by isoniazid poisoning in a patient treated with pyridoxine and hemodialysis

Isoniazid is widely used to treat tuberculosis. In populations with a high prevalence rate of tuberculosis, acute ingestion of isoniazid has been reported as a potential cause of coma. In this study, we present the diagnosis and treatment of isoniazid poisoning in a case with acute coma as the major clinical presentation.A 32-year-old male who ingested 12 g isoniazid (2 hours prior to medical attention) was brought to the emergency department while in a coma and experiencing frequent seizures. Initial treatment with large doses of pyridoxine (for 6 hours) failed to awaken this patient. The patient was then given hemodialysis and pyridoxine; after 3 days he awoke from coma, with no further reported seizures.Isoniazid poisoning should be suspected in patients whose major symptoms are coma and seizure, especially those who have access to isoniazid. Monitoring the blood level of isoniazid will establish the diagnosis and help clinical management. A combination of hemodialysis and pyridoxine is effective in treating isoniazid poisoning.

Acute isoniazid toxicity and the need for adequate pyridoxine supplies

A 25-year-old, 54-kg Hispanic man who had recently started multidrug therapy for pulmonary tuberculosis presented in status epilepticus after ingesting 9 g of isoniazid in a suicide attempt. Successful management of this patient required collaboration between several institutions to provide the large amount of necessary intravenous pyridoxine. Ultimately, this single overdose depleted the supply of intravenous pyridoxine for a significant region of the state of Nebraska. Isoniazid is commonly used to treat tuberculosis, but it is encountered relatively infrequently as the cause of an acute overdose. Severe isoniazid overdoses may present as seizure activity that is refractory to conventional antiepileptic therapy. Although intravenous pyridoxine is an effective antidote for isoniazid overdoses in patients presenting with status epilepticus, this agent has few indications and is typically stocked in limited quantities. In regions with large populations of patients who receive antituberculosis therapy, collaborative networks must be created to ensure that adequate supplies of intravenous pyridoxine (> or = 20 g) are available for effective treatment of isoniazid poisonings.

Pyridoxine in clinical toxicology: a review

Pyridoxine (vitamin B6) is a co-factor in many enzymatic pathways involved in amino acid metabolism: the main biologically active form is pyridoxal 5-phosphate. Pyridoxine has been used as an antidote in acute intoxications, including isoniazid overdose, Gyromitra mushroom or false morrel (monomethylhydrazine) poisoning and hydrazine exposure. It is also recommended as a co-factor to improve the conversion of glyoxylic acid into glycine in ethylene glycol poisoning. Other indications are recommended by some sources (for example crimidine poisoning, zipeprol and theophylline-induced seizures, adjunct to d-penicillamine chelation), without significant supporting data. The value of pyridoxine or its congener metadoxine as an agent for hastening ethanol metabolism or improving vigilance in acute alcohol intoxication is controversial. This paper reviews the various indications of pyridoxine in clinical toxicology and the supporting literature. The potential adverse effects of excessive pyridoxine dosage will also be summarized.

Antibiotic-induced convulsions

Convulsive episodes are associated with the use of a number of antimicrobial agents. Although seizures may be a feature of the disease being treated, antibiotics should be considered possible causes of seizures, particularly if suggested by temporal relationships between seizure activity and drug administration. The astute clinician should be aware of the clinical settings in which antibiotic-induced seizures occur, be familiar with likely agents and their mechanisms of toxicity, and be prepared to institute appropriate management directed at this adverse effect of antimicrobial therapy.

Alcohol-related seizures, Part II: Clinical presentation and management

Alcoholism may be society's most devastating problem short of war and malnutrition. Perhaps the most complex and preplexing medical complication of alcoholism is alcohol-related seizures. This article is a collective review designed to provide emergency physicians with an overview of the topic that is pertinent to their clinical practice. Part 1 addressed the pathophysiology, differential diagnosis, and evaluation of alcohol-related seizures. Part 2 focuses on the clinical presentation, management, and disposition. In addition, a classification of alcohol-related seizures is proposed.