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TRICYCLIC ANTIDEPRESSANT OVERDOSE


About Your Diagnosis

Tricyclic antidepressants are, as the name states, a class of drugs used in the treatment of depression. Tricyclic antidepressants can also be used in the treatment of migraine headache and neuropathic pain (pain originating from compression of nerves or from direct nerve involvement, e.g., diabetic neuropathy). Included in this class of drugs are amitriptyline, imipramine, nortriptyline, desipramine, doxepin, and the related agents amoxapine, bupropion, and trazodone. Overdosing on tricyclic antidepressants can lead to involvement of many organ systems but primarily affects the heart and the brain. In 1995, over 20,000 cases of tricyclic antidepressant overdoses were reported in the United States, and of those reported, nearly 2% of patients died from the overdose. Most of the cases were intentional and not accidental.

Suicide notes and family statements of intentional ingestion of extra pills usually make the diagnosis of tricyclic antidepressant overdose obvious. Physical findings, blood tests, and electrocardiograms (ECG) can help confirm, monitor, and offer prognosis in overdose patients. Tricyclic antidepressant overdose can be cured, but it can also be fatal if life-threatening symptoms occur before the patient arrives in the emergency room.

Living With Your Diagnosis

Agitation, lethargy, seizures, muscle twitching, and jerking muscle movements are many findings that can occur with tricyclic overdose. Many patients present in a coma with an extremely low blood pressure and rapid heart rate. Life-threatening heart rhythm disturbances called ventricular tachycardia, heart blocks, and electromechanical dissociation (see Patient Teaching Guide for this topic) can all occur. Tricyclics can significantly decrease the heart's pumping ability, leading to shock and death.

Certain blood tests may be ordered to rule out other pill or drug ingestion. Perhaps the most important laboratory test to follow is the ECG, since specific findings are associated with antidepressant overdose.

Treatment

The treatment of tricyclic antidepressant overdose is generally similar to treatment for any poisoned patient. The initial treatment is to stabilize the vital signs. Typically, the patient has low blood pressure, and this must first be treated with intravenous fluids. If this is unsuccessful, specific agents called vasopressors can be used to maintain blood pressure. Life-threatening rhythms must be treated immediately. Establishing an airway for breathing, especially in the comatose individual, may require a breathing machine called a ventilator. If the patient is presenting with seizures, antiseizure medications such as diazepam, dilantin, and phenobarbital can be used.

Once the life-threatening emergencies are controlled, the key to treating tricyclic antidepressants overdose is to "decontaminate" the bowel. This means preventing further absorption of the drug through the stomach by using activated charcoal at frequent dosages. The activated charcoal binds to the antidepressant, thereby preventing its absorption. In addition, magnesium citrate can be given to speed up the removal of the drug from the gastrointestinal tract.

There is no real antidote for tricyclic antidepressants. Some physicians may try sodium bicarbonate to help block the drug's effect on the heart and the heart's electrical system.

The patient is admitted to either the intensive care unit or a bed where the heart can be monitored.

The DOs
  • Realize that patients may not appear ill at first but can rapidly develop many life-threatening complications. For this reason, most patients are admitted and monitored. In addition, most of the cases are intentional drug overdoses and further psychiatric evaluations are needed once the medical emergency is stabilized.
  • Take prescriptions as directed. Tricyclic antidepressants can be toxic when accidentally ingested.
  • Seek psychiatric help if you have any suicidal thoughts.
The DON'Ts
  • Don't use alcohol with antidepressant medications. Alcohol is not a stimulant! Alcohol is a depressant.
  • Don't forget that depression is a common disease. The best form of treatment is with medications. Tricyclic antidepressants are good agents to use, but they must be used properly. The total duration of treatment for depression varies from individual to individual but typically lasts at least 6 months. It is also important to remember that the response to treatment can take up to 2 months.
When to Call Your Doctor
  • If you have any suicidal or homicidal ideas.
  • If you are depressed.
For More Information
For a listing by state of poison centers certified by The American Association of Poison Control Center (AAPCC)
http://medicine.net.com

 

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