Class 1a quinidine, procainamide, disopyramide and class 1c drugs such as flecainide, prolong depolarisation in a similar fashion to tricyclics. Likewise class 3 drugs bretylium, amiodarone also prolong the QT interval and may predispose to arrhythmias. Lignocaine lidocaine has been reported as being effective in the treatment of frequent ventricular ectopics in 13 overdose patients but in some patients the ectopics persisted for up to 72 hours.
Phenytoin is a class 1b agent, which, unlike 1a and 1c drugs, can increase the rate of phase 0 depolarisation. Boehnert described the successful treatment of ventricular arrhythmias in three patients with the use of phenytoin.
Animal experiments have failed to show any significant benefit from phenytoin in the prevention or management of arrhythmias. The use of glucagon in one patient was reported to increase blood pressure and reduce the QRS duration but sodium bicarbonate had also been given shortly before the glucagon.
Magnesium sulphate has been used successfully in an overdose patient with refractory ventricular fibrillation. Physostigmine is a short acting cholinesterase inhibitor that was proposed in the s as a treatment for arrhythmias. Since then, however, it has been described as causing asystole 72 and seizures. Hypotension is thought to result from a combination of decreased myocardial contractility and peripheral vasodilatation. In cases refractory to the use of intravenous fluids the use of inotropic agents may be required.
Norepinephrine has been found to be more effective than dopamine in the management of hypotension, possibly as the effect of dopamine partially depends on the release of endogenous norepinephrine stores that are depleted in tricyclic overdose because of reuptake inhibition.
Extracorporal circulation has been used in patients who have not improved with the use of inotropes 78 , 79 and experimental work in pigs has demonstrated increased survival with this technique.
Where patients have a cardiac arrest after ingestion of tricyclics recovery is possible even after prolonged resuscitation. Patients have recovered after three and five hours of external cardiac massage. Seizures are usually self limiting but where treatment is necessary benzodiazepines are the treatment of choice. Tricyclic specific antibody fragments have been developed and their effectiveness at reversing cardiovascular toxicity in animals has been demonstrated by several studies.
A case report of their clinical use indicates an improvement in QRS and QT intervals but sodium bicarbonate had also been given. Tricyclics have a very large volume of distribution and this restricts the role of methods designed to increase drug clearance from the intravascular space. The treatment of eight patients with resin haemoperfusion removed no more than 3.
Several reports have found that all major complications will be apparent within six hours of ingestion 23 , 91 , 92 and that the incidence of late complications is extremely low.
Patients should have cardiac monitoring until the electrocardiogram has been normal for 12 to 24 hours. It has been reported that the advice from the British poisons centres concerning the management of tricyclic overdose is not uniform. There are limited data and much of the evidence quoted is derived from animal studies, case reports or small series of healthy subjects.
The quality of this information results in variable interpretations and seems to cause some ambiguity in the advice given. In the absence of further evidence a consensus approach to the management of tricyclic overdose with national guidelines could avoid confusion when medical staff seek advice from the poisons centres.
Monitoring: Patients who display signs of toxicity should be monitored for a minimum of 12 hours. Gary Kerr initiated the review, performed the original literature search and wrote the first draft. Crawford McGuffie and Stewart Wilkie undertook literature searchs, edited and wrote further drafts. Gary Kerr will act as guarantor. You will be able to get a quick price and instant permission to reuse the content in many different ways.
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Forgot your log in details? Register a new account? Forgot your user name or password? Search for this keyword. Advanced search. Latest content Current issue Archive Authors About. Log in via Institution. Email alerts. Article Text. Article menu. Tricyclic antidepressant overdose: a review. Abstract Overdoses of tricyclic antidepressants are among the commonest causes of drug poisoning seen in accident and emergency departments.
Statistics from Altmetric. The toxic effects of tricyclics are caused by four main pharmacological properties: Inhibition of norepinephrine reuptake at nerve terminals. A membrane stabilising or quinidine-like effect on the myocardium. Anticholinergic action. Clinical features The dose ingested, even if reliably confirmed, is a poor predictor of the subsequent clinical outcome.
View this table: View inline View popup. Table 1 Clinical features and complications of tricyclic antidepressant overdose. Investigations Plasma tricyclic concentrations are not widely available and measured levels often lack sensitivity in detecting active metabolites. Conclusion It has been reported that the advice from the British poisons centres concerning the management of tricyclic overdose is not uniform. Appendix: management plan for treatment of tricyclic overdose Assess and treat ABCs as appropriate.
Give 50 grams of charcoal if within one hour of ingestion. Give sodium bicarbonate 50 ml of 8. Hypotension: Give intravenous fluids Consider inotropes Cardiac arrest: Prolonged resuscitation may be successful Monitoring: Patients who display signs of toxicity should be monitored for a minimum of 12 hours.
Acknowledgments Contributors Gary Kerr initiated the review, performed the original literature search and wrote the first draft. Suicidal attempt by imipramine overdose. BMJ ; 1 : —9. Self-poisoning in Newcastle,— Med J Aust ; : —3. Obafunwa JO, Busuttil A. Deaths from substance overdose in the Lothian and Borders region of Scotland — Hum Exp Toxicol ; 13 : —6. Survey of drug related deaths in Victoria. Med J Aust ; : — Relative mortality from overdose of antidepressants.
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Effect of activated charcoal on absorption of nortriptyline. Lancet ; ii : —5. Swartz C, Sherman A. The treatment of tricyclic antidepressant overdose with repeated charcoal. J Clin Psychopharmacol ; 4 : — Effect of delayed administration of activated charcoal on nortriptyline absorption.
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Select language. Tricyclic antidepressant overdose. Last reviewed: 14 Dec Last updated: 04 Feb Hypertonic sodium bicarbonate improves conduction abnormalities and hypotension. Benzodiazepines are the first-line treatment for seizures.
Key diagnostic factors change in mental status tachycardia hypotension mydriasis warm, dry, flushed skin change in mental status decreased or absent bowel sounds urinary retention ophthalmic signs neurological signs More key diagnostic factors. Other diagnostic factors features of serotonin syndrome Other diagnostic factors. Risk factors history of depression obsessive-compulsive disorder chronic pain attention deficit hyperactivity disorders More risk factors.
Investigations to consider serum TCA concentrations serum acetaminophen concentrations serum salicylate concentrations urine drug screen More investigations to consider. Differentials Overdose of sodium channel blockers Conditions causing right axis ECG deviation Anticholinergic overdose More differentials.
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