Tricyclic antidepressant poisoning. Reversal of coma, choreoathetosis, and myoclonus by physostigmine

Toxicologic Confounders of Brain Death Determination: A Narrative Review

The aim of this narrative review is to describe the toxicologic confounders of brain death currently reported in the literature to offer guidance for physicians assessing brain death after a toxic exposure. We established an a priori definition of a “brain death mimic” as an unresponsive, intubated patient missing some, but not all brainstem reflexes. We completed a review of the literature utilizing MEDLINE and EMBASE to find case reports of patients of all ages in English, French, and Spanish meeting the criteria and hand searched the references of the results. We recorded xenobiotic dose, duration of physical exam suggesting brain death, and how the cases failed to meet full brain death criteria, when available. Fifty-six cases representing 19 different substances met the a priori definition of brain death mimic. Xenobiotic toxicities included: snake envenomation (13), baclofen (11), tricyclic antidepressants (8), bupropion (7), alcohols (4), antiepileptic agents (3), barbiturates (2), antidysrhythmics (2), organophosphates (2), and one case each of magnesium, succinylcholine, tetrodotoxin, and zolpidem. All patients except one survived to discharge and the majority at their baseline physical health. The most common means by which the cases failed brain death examination prerequisites was via normal neuroimaging. The xenobiotics in this review should be considered in cases of poisoning resulting in loss of brainstem reflexes and addressed before brain death determination. Brain death diagnosis should not be pursued in the setting of normal cerebral imaging or incomplete evaluation of brain death prerequisites.

Adverse Effects of Physostigmine

INTRODUCTION

Physostigmine is a tertiary amine carbamate acetylcholinesterase inhibitor. Its ability to cross the blood-brain barrier makes it an effective antidote to reverse anticholinergic delirium. Physostigmine is underutilized following the publication of patients with sudden cardiac arrest after physostigmine administration in patients with tricyclic antidepressant (TCA) overdoses. We completed a narrative literature review to identify reported adverse effects associated with physostigmine administration.

DISCUSSION

One hundred sixty-one articles and a total of 2299 patients were included. Adverse effects occurred in 415 (18.1%) patients. Hypersalivation (206; 9.0%) and nausea and vomiting (96; 4.2%) were the most common adverse effects. Fifteen (0.61%) patients had seizures, all of which were self-limited or treated successfully without complication. Symptomatic bradycardia occurred in 8 (0.35%) patients including 3 patients with bradyasystolic arrests. Ventricular fibrillation occurred in one (0.04%) patient with underlying coronary artery disease. Of the 394 patients with TCA overdose, adverse effects were described in 14 (3.6%). Adverse effects occurred in 7.7% of patients treated with an overdose of an anticholinergic agent compared with 20.6% of patients with non-anticholinergic agents. Five (0.22%) fatalities were identified.

CONCLUSIONS

In conclusion, significant adverse effects associated with the use of physostigmine were infrequently reported. Seizures were self-limited or resolved with benzodiazepines, and all patients recovered neurologically intact. Physostigmine should be avoided in patients with QRS prolongation on EKG, and caution should be used in patients with a history of coronary artery disease and overdoses with QRS prolonging medications. Based upon our review, physostigmine is a safe antidote to treat anticholinergic overdose.

Timing and frequency of physostigmine redosing for antimuscarinic toxicity

We sought to determine how frequently antimuscarinic-poisoned patients receiving physostigmine receive multiple doses of physostigmine, the length of time between physostigmine doses, and what impact multiple doses of physostigmine have on the disposition and total length of hospital stay. We performed a retrospective chart review of patients given physostigmine for likely antimuscarinic toxicity. A total of 45 patients met inclusion criteria. We abstracted patient demographics, vital signs, physical exam findings, electrocardiograms, the timing and dose of physostigmine, the implicated antimuscarinic agents, and disposition from the hospital. We counted the number of patients who required multiple physostigmine doses and calculated the time to repeat dosing. Fourteen of the 45 patients (31%) given physostigmine for antimuscarinic toxicity received multiple doses: nine patients (20%) received two doses, three patients (6.6%) received three doses, and two patients (4.4%) received four doses. Less than 5.5 h elapsed between sequential physostigmine doses, and less than 6.5 h elapsed between the first and last dose. Forty-five percent of patients receiving one dose of physostigmine were discharged from the emergency department (ED) and 36% of patients receiving more than one dose of physostigmine were discharged from the ED. Whether admitted or discharged, there was no statistically significant difference in the length of hospital stay between patients receiving one or multiple doses of physostigmine. Repeated physostigmine administration is not frequently needed in medication-induced antimuscarinic toxicity. Patients are not likely to require further physostigmine redosing more than 6.5 h from their first dose.

[Hypotensive cardio-circulatory failure and metabolic acidosis after suicidal intoxication with trimipramine and quetiapine. Case report and background]

The case of a 44-year-old female patient is reported, who ingested trimipramine and quetiapine in a suicide attempt. Initially sinus tachycardia and hypotension were seen, which resulted in a hypotensive cardio-circulatory failure despite fluid therapy and administration of catecholamines. Because of the life-threatening situation and the fact that the ingestion was 2 h prior to admission, a rapid transport to the next hospital was preferred to treatment with active charcoal. Intoxication with tricyclic antidepressants are very common in Europe and have a mortality of up to 15% in severe cases. The specific therapy consists of airway management, hemodynamic stabilization and primary elimination of the poison. Secondary detoxication is less important. The administration of the antidote physostigmine is controversial but carbo medicinalis should be given orally or via a gastric tube.

Drug-induced myoclonus: frequency, mechanisms and management

Myoclonus is a sudden, abrupt, brief, 'shock-like' involuntary movement caused by muscular contractions ('positive myoclonus') or a sudden brief lapse of muscle contraction in active postural muscles ('negative myoclonus' or 'asterixis'). Various disorders can cause myoclonus including neurodegenerative and systemic metabolic disorders and CNS infections. In addition, myoclonus has been described as an adverse effect of some drugs. Level II evidence is available to indicate that levodopa, cyclic antidepressants and bismuth salts can cause myoclonus, while there is less robust evidence to associate numerous other drugs with the induction of myoclonus. The pharmacological mechanisms responsible for this adverse effect are not well established, although increased serotonergic transmission may be involved in the induction of myoclonus by several drugs. Drug-induced myoclonus usually resolves after withdrawal of the offending drug, but in some cases specific treatments are needed.

Assessing physostigmine's contraindication in cyclic antidepressant ingestions

Ingestion of cyclic antidepressant medications or prolongation of the electrocardiographic QRS interval are commonly considered as contraindications to the use of physostigmine as an antidote for antimuscarinic toxicity. This dictum seems to stem from a few well-publicized cases in which administration of physostigmine was temporally associated with the development of asystole. Before the report of these cases, physostigmine was more frequently used and had been considered a first-line antidote for both the neurologic and cardiac toxic effects of cyclic antidepressant overdose. This apparent inconsistency, and a resurgence of interest in physostigmine as an antidote, begs the question of the appropriateness of this drug's contraindication in all cyclic antidepressant ingestions. Review of the published clinical and experimental evidence provides little support for the clinical utility of using electrocardiographic criteria or the ingestion of cyclic antidepressants as contraindications to the use of physostigmine.

Anticholinergic poisoning with adulterated intranasal cocaine

In recent years, emergency physicians have encountered a growing number of patients who present with anticholinergic toxicity after using adulterated heroin. Anticholinergic poisoning caused by adulterated cocaine is far less common. This report describes the case of a 39-year-old man who arrived in the emergency department several hours after the nasal insufflation of cocaine. Classic symptoms of anticholinergic toxicity were evident on examination, including dry, flushed skin, agitation, tachycardia, mydriasis, and absence of bowel sounds. Treatment included intravenous fluids and lorazepam, with resolution of symptoms over several hours. Urine samples revealed the presence of cocaine metabolites as well as the anticholinergic drug atropine, and infrequently encountered adulterant of cocaine. Anticholinergic poisoning is reviewed, and the physical examination findings that distinguish this syndrome from the closely related sympathomimetic syndrome typical of cocaine are detailed. Current treatment recommendations for anticholinergic poisoning are summarized.

Cyclic antidepressant overdose: a review of current management strategies

Cyclic antidepressant (CA) overdose can produce life-threatening seizures, hypotension, and dysrhythmias. It accounts for up to half of all overdose-related adult intensive care unit admissions and is the leading cause of death from drug overdose in patients arriving at the emergency department alive. Several factors contribute to the significant morbidity and mortality associated with CA overdose. First, CAs are widely prescribed and are dispensed to patients at increased risk for attempting suicide. Second, drugs of this class generally have a low therapeutic toxic ratio. Third, in the majority of fatal cases, the patient dies before reaching a hospital. Finally, and of greatest significance for the clinician, the presenting signs and symptoms of CA overdose may be missed by the physician, even in cases of severe toxicity. Therefore, CAs must be considered early in any case of suspected overdose, and all such cases should be managed as potentially fatal ones. The following case demonstrates the current approach to the patient with significant CA toxicity.

Neural symptoms induced by tricyclic antidepressants: phenomenology and pathophysiology

The authors review the literature describing the neural symptoms induced by tricyclic antidepressants, especially tremor, seizures, akathisia, myoclonus, dyskinesia and delirium. Sedation, modifications of sleep, memory and appetite are also described. Tremor and myoclonus are the most frequent drug-induced neural symptoms. Delirium is most often caused by high-dosage treatments. The pathophysiology of akathisia and dyskinesia raises important questions concerning the mode of action of antidepressants.

Reversal of orphenadrine-induced ventricular tachycardia with physostigmine

A 3-year-old boy developed confusion, generalized tonic-clonic seizures, and sustained ventricular tachycardia following ingestion of an unknown quantity of orphenadrine (Norflex). Although refractory to precordial thump, synchronous cardioversion, and lidocaine, the ventricular tachycardia was reversed by intravenous administration of the tertiary acetylcholinesterase inhibitor physostigmine. We discuss the underlying physiology and manifestations of anticholinergic overdose, the specific manifestations of orphenadrine overdose, and the current recommendations regarding the utilization and toxicity of physostigmine in the treatment of anticholinergic syndromes and orphenadrine intoxication.

Clinical features, pathogenesis and management of drug-induced seizures

Many classes of pharmacological agents have been implicated in cases of drug-induced seizures. The list includes antidepressant drugs, lithium salts, neuroleptics, antihistamines (H1-receptor antagonists), anticonvulsants, central nervous system stimulants, general and local anaesthetics, antiarrhythmic drugs, narcotic and non-narcotic analgesics, non-steroidal anti-inflammatory drugs, antimicrobial agents, antifungal agents, antimalarial drugs, antineoplastic drugs, immunosuppressive drugs, radiological contrast agents and vaccines. For each of these classes of drugs, this article offers a revision of the literature and emphasises in particular the frequency of the adverse reaction, its clinical presentation, its presumed epileptogenic mechanism and the therapeutic strategy for the management of drug-induced seizures. An attempt is also made to distinguish seizures induced by standard dosages from those provoked by accidental or self-induced intoxication. For some classes of drugs such as antidepressants, neuroleptics, central nervous system stimulants (e.g. theophylline, cocaine, amphetamines) and beta-lactam antibiotics, seizures are a well recognised adverse reaction, and a large body of literature has been published discussing exhaustively the major aspects of the issue; sufficient data are available also for the other classes of pharmacological agents mentioned above. In contrast, several other drugs [e.g. allopurinol, digoxin, cimetidine, protirelin (thyrotrophin releasing hormone), bromocriptine, domperidone, insulin, fenformin, penicillamine, probenecid, verapamil, methyldopa] have not been studied thoroughly under this aspect, and the only source of information is the occasional case report. This review does not address the issue of seizures induced by drug withdrawal.

Phenytoin: does it reverse tricyclic-antidepressant-induced cardiac conduction abnormalities?

Case reports have appeared describing a beneficial effect of phenytoin in reversing cardiac conduction abnormalities induced by tricyclic antidepressant (TCA) overdose. Controlled studies have not been published. The following questions were addressed using intravenous amitriptyline and phenytoin in a rabbit model: Can prophylaxis with phenytoin before amitriptyline poisoning forestall the onset of cardiac abnormalities? Would such prophylactic phenytoin administration allow a higher dose of amitriptyline before death occurs? Would phenytoin reverse the cardiotoxic effects of amitriptyline once in progress? Animals were used in repeated trials with one-week "washout" intervals and served as their own controls in all but the final trial. Prophylactic phenytoin did not change the potency of amitriptyline in inducing abnormal cardiac performance, nor did it allow the animals to be titrated to a higher dose of amitriptyline before death occurred. In 12 animals, phenytoin "rescue" at the point of a widened QRS or arrhythmia was attempted. Two showed improvement; the remainder did not. Because this portion of the experiment was neither blinded nor controlled, nor were respirations or blood pressure monitored, these results must be viewed cautiously. Although our results suggest that prophylactic phenytoin is not useful, its role in therapy of occasional cases requires further investigation.

Changes in body temperature after administration of adrenergic and serotonergic agents and related drugs including antidepressants: II

This survey continues a second series of compilations of data regarding changes in body temperature induced by drugs and related agents. The information listed includes the species used, the route of administration and dose of drug, the environmental temperature at which experiments were performed, the number of tests, the direction and magnitude of change in body temperature and remarks on the presence of special conditions, such as age or brain lesions. Also indicated is the influence of other drugs, such as antagonists, on the response to the primary agent. Most of the papers were published from 1980 to 1984 but data from many earlier papers are also tabulated.

Tricyclic antidepressant poisoning. Management of arrhythmias

Deaths from tricyclic antidepressant (TCA) overdose are usually due to arrhythmias and/or hypotension. Tricyclic antidepressant toxicity is due mainly to the quinidine-like actions of these drugs on cardiac tissues. Slowing of phase 0 depolarisation of the action potential results in slowing of conduction through the His-Purkinje system and myocardium. Slowed impulse conduction is responsible for QRS prolongation and atrioventricular block, and contributes to ventricular arrhythmias and hypotension. Therapies that improve conduction, e.g. hypertonic sodium bicarbonate, are useful in treating these toxic effects. Other mechanisms contributing to arrhythmias include abnormal repolarisation, impaired automaticity, cholinergic blockade and inhibition of neuronal catecholamine uptake. Toxicity may be worsened by acidaemia, hypotension or hyperthermia. Sinus tachycardia is due to the anticholinergic effects of the tricyclic antidepressants as well as blockade of neuronal catecholamine reuptake. Sinus tachycardia is generally well-tolerated and requires no therapy. Sinus tachycardia with QRS prolongation may be difficult to distinguish from ventricular tachycardia. Electrocardiograms obtained using oesophageal or atrial electrodes may be useful in determining the relationship of atrial and ventricular activity. Although QRS prolongation alone is not compromising, it is a marker for patients at highest risk of developing seizures, arrhythmias or hypotension. Ventricular tachycardia (monomorphic) is a consequence of impaired myocardial depolarisation and impulse conduction. Hypertonic sodium bicarbonate may partially correct impaired conduction and be of benefit in treating ventricular tachycardia. Since hypertonic sodium bicarbonate appears to act by increasing the extracellular sodium concentration as well as by increasing extracellular pH, hyperventilation may be less effective. Hypertonic sodium bicarbonate is of particular benefit in patients who are acidotic, since acidosis aggravates cardiac toxicity. However, administration of hypertonic sodium bicarbonate is beneficial even when blood pH is normal. Lignocaine (lidocaine) may be useful in treating ventricular tachycardia but should be administered cautiously to avoid precipitating seizures. Ventricular bradyarrhythmias are due to impaired automaticity or depressed atrioventricular conduction and can be treated by placement of a temporary pacemaker, or with a chronotropic agent, e.g. isoprenaline (isoproterenol), with or without concomitant vasoconstrictors.(ABSTRACT TRUNCATED AT 400 WORDS)

Toxic "ictal" confusion in middle age: treatment with benzodiazepines

In adult and elderly non-epileptic subjects psychoactive drugs may cause an altered state of consciousness and repetitive irritative EEG discharges. The neurotoxic pathogenesis of this drug-induced confusion and the differentiation from absence status are discussed. Dramatic relief by intravenous benzodiazepines is detailed. Recovery is complete and prognosis is excellent on withdrawal of the offending drug.

Failure of physostigmine in intoxications with tricyclic antidepressants in rats

In experiments on rats there is a moderate antagonistic effect of physostigmine against intoxications with the tricyclic antidepressants (TAD) clomipramine, desipramine and imipramine, respectively. During the first hours after TAD intoxication the survival rate is higher in physostigmine treated rats. Especially after relatively low doses of TAD the lethality seems to be reduced by physostigmine treatment. However, at the end of the observation period (96 h) the lethality after TAD is equal with and without physostigmine treatment. The effectivity of physostigmine does not depend on the mode of administration: repeated administration and intravenous infusion are not more effective than a single injection of physostigmine. The influence of TAD on heart rate and respiratory rate was not abolished by physostigmine salicylate. Intoxications with high doses of physostigmine were antagonized by atropine; on the other hand there are no signs for an antagonistic effect of desipramine against physostigmine intoxication, that means their anticipated anticholinergic properties could not be proved.

Treatment of imipramine overdose in children

Enuresis is a common problem often treated effectively with imipramine hydrochloride. The usefulness of this therapy carries with it, however, the risk of accidental overdose by younger siblings of these enuretic patients. Traditional support measures are effective in the treatment of the mild to moderate overdose, while separate symptomatic treatment of seizures and cardiac arrhythmias is possible as outlined herein. Physostigmine offers a single alternate treatment which is effective in the full panorama of life-threatening manifestations of an imipramine overdose.

Experiences with physostigmine in the reversal of adverse post-anaesthetic effects

Physostigmine salicylate has proved to be a very useful agent for use in the recovery room. All but two of our first 110 patients receiving it were returned to full consciousness, whether they had been comatose or agitated. In our hands it has been used to reverse the adverse central effects of tranquilizers, antihistamines and belladonna alkaloids.

Physostigmine--its use and abuse

Physostigmine salicylate, a cholinesterase inhibitor, has been shown to reverse the effects of certain drugs with anticholinergic properties. The paper provides a brief historical account of physostigmine, reviews the cholinergic drugs and their effects and suggests a management protocol based on physiologic criteria. Twenty-six overdose cases, recently treated with physostigmine, are summarized. The controversy regarding the etiology of seizures following physostigmine administration is discussed.