Tricyclic antidepressant overdose is poisoning caused by overuse of tricyclic antidepressant (TCA) type. Symptoms include high body temperature, blurred vision, dilated pupils, drowsiness, confusion, convulsions, rapid heartbeat, and heart attacks. If symptoms do not occur within six hours of exposure they are unlikely to occur.
TCA overdose may occur accidentally or intentionally in an attempt to cause death. The toxic dose depends on the specific TCA. Most are non-toxic less than 5 mg/kg except for desipramine, nortriptyline, and trimipramine, which are generally non-toxic at less than 2.5 mg/kg. In young children one or two pills can be fatal. Electrocardiogram (ECG) should be included in the assessment when there is concern overdose.
In the active charcoal overdose is often recommended. One should not be forced to vomit. In those with a wide QRS complex ( & gt; 100 ms ) sodium bicarbonate is recommended. If seizures occur benzodiazepines should be given. In those with low blood pressure, intravenous fluids and norepinephrine may be used. The use of intravenous lipid emulsions can also be tried.
In the early 2000s TCA was one of the most common causes of poisoning. In the United States in 2004 there were more than 12,000 cases. In the UK they produce about 270 deaths per year. The overdose of TCA was first reported in 1959.
Video Tricyclic antidepressant overdose
Signs and symptoms
The peripheral autonomic nervous system, the central nervous system and the heart are the main systems affected after an overdose. Initial or mild symptoms usually develop within 2 hours and include tachycardia, drowsiness, dry mouth, nausea and vomiting, urinary retention, confusion, agitation, and headache. More severe complications include hypotension, heart rhythm disturbances, hallucinations, and seizures. Electrocardiogram (EKG) disorders are common and various types of cardiac dysrhythmias may occur, the most common being the tachycardia sinus and intraventricular conduction delay resulting in an extension of the QRS complex and the PR/QT interval. Seizures, heart dysrhythmias, and apnea are the most important life-threatening complications.
Maps Tricyclic antidepressant overdose
Cause
Tricyclics has a narrow therapeutic index, ie , therapeutic doses approaching toxic doses. Factors that increase the risk of toxicity include advanced age, cardiac status, and the use of other drugs simultaneously. However, serum drug levels are not useful for evaluating the risk of arrhythmias or seizures in tricyclic overdoses.
Pathophysiology
Most of the toxic effects of TCA are caused by four major pharmacological effects. TCA has an anticholinergic effect, causing excessive blockade of norepinephrine reuptake in preganglionic synapses, direct alpha adrenergic blockade, and importantly they block sodium membrane channels by slowing membrane depolarization, thus having a quinidine-like effect on myocardium.
Diagnosis
Special blood tests to verify toxicity are usually not available. Electrocardiogram (ECG) should be included in the assessment when there is concern overdose.
Treatment
Persons with symptoms are usually monitored in the intensive care unit for at least 12 hours, with careful attention to airway maintenance, along with blood pressure monitoring, arterial pH, and ongoing EKG monitoring. Supportive therapy is given when necessary, including respiratory support and maintenance of body temperature. Once a person has had a normal ECG for more than 24 hours they are generally medically clear.
Decontamination
The initial treatment of an acute overdose includes gastric decontamination. This is achieved by giving the activated charcoal, which adsorb drugs in the gastrointestinal tract either through the mouth or via a nasogastric tube. Active charcoal is very useful if given within 1 to 2 hours after consumption. Other decontamination methods such as gastric pumps, ipecac-induced emesis, or overall intestinal irrigation are generally not recommended in TCA poisoning. Gastric pumps can be considered within an hour after swallowing but evidence to support this practice is bad.
Medication
Intravenous administration of sodium bicarbonate as an antidote has been shown to be an effective treatment for resolving metabolic acidosis and cardiovascular complications of TCA poisoning. If sodium bicarbonate therapy fails to improve cardiac symptoms, conventional or magnesium antidysrhythmias may be used to reverse cardiac abnormalities. However, no benefit was demonstrated from Class 1 antiarrhythmic drugs; they seem to aggravate the blockade of sodium channels, slow conduction velocities, and suppress contractility and should be avoided in TCA poisoning. Low blood pressure was initially treated with a liquid along with bicarbonate to reverse metabolic acidosis (if present), if blood pressure remained low despite fluid then further action such as epinephrine, norepinephrine or dopamine may be used to increase blood pressure.
Another potentially severe symptom is seizures: Seizures often heal without treatment but other benzodiazepine or anticonvulsive administration may be necessary for persistent muscle overactivity. There is no role for physostigmine in the treatment of tricyclic toxicity because it can increase cardiac toxicity and cause seizures. In cases of severe refractory TCA overdose, intravenous lipid emulsion therapy has been reported to improve signs and symptoms in patients suffering from toxicity involving several types of lipophilic substances, therefore lipids may have a role in treating severe refractory cases. TCA Overdose.
Dialysis
Tricyclic antidepressants are highly attached to proteins and have large distribution volumes; therefore the removal of these compounds from the blood by hemodialysis, hemoperfusion or other techniques may not be of significant use.
Epidemiology
Studies in the 1990s in Australia and the UK showed that between 8 and 12% of drug overdoses followed TCA consumption. TCA can be involved up to 33% of all fatal poisoning, second only to analgesics. Another study reported 95% of antidepressant deaths in England and Wales between 1993 and 1997 were associated with tricyclic antidepressants, notably dothiepines and amitriptyline. Specified there are 5.3 deaths per 100,000 recipes. Sodium channel blockers such as Dilantin should not be used in TCA overdose treatment because Na blockade will increase QTI.
References
External links
Source of the article : Wikipedia
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