Antidepressants overdose

Tricyclic (TCAs) overdoses account for most of the hospital admissions and deaths due to antidepressant therapy.

 Tricyclic antidepressant overdoses often require more aggressive intervention.

 A majority of these deaths are attributable to cardiac complications.

Trazodone, one is not commonly associated with cardiac arrhythmias thus patients generally require only emesis and/or gastric lavage, and minimal supportive therapy,

 

Tricyclic (TCAs) medical complications

Cardiovascular effects

 The most important toxic effect of tricyclics is the slowing of depolarisation of the cardiac action potential by inhibition of the sodium current and this delays propagation of depolarization through both myocardium and conducting tissue.

Central nervous system effects; seizures may occur.

 

Management of TCA overdose

Reducing absorption

Activated charcoal may reduce the absorption of tricyclics and the benefits of both single and multiple doses have been described.

Alkalinisation; Administration of sodium bicarbonate in tricyclic intoxication has beneficial effects. 

CNS complications

Seizures are usually self limiting but where treatment is necessary benzodiazepines are the treatment of choice.

Monitoring

Patients should have cardiac monitoring until the electrocardiogram has been normal for 12 to 24 hours.

 

Management plan for treatment of tricyclic overdose

1.      Assess and treat ABCs as appropriate.

2.      Examine for clinical features

                                                               i.      Check urea and electrolytes—look for low potassium

                                                             ii.      Check arterial blood gases—look for acidosis

                                                            iii.      Perform electrocardiograph—look for QRS>0.16 seconds

3.      Consider gastric lavage only if within one hour of a potentially fatal overdose.

4.      Give 50 grams of charcoal if within one hour of ingestion.

5.      Give sodium bicarbonate (50 ml of 8.4%) if:

                                                         i.            pH <7.1

                                                       ii.            RS >0.16 seconds

                                                      iii.            Arrhythmias

                                                     iv.            Hypotension

Arrhythmias: Avoid antiarrhythmics

ü  Correct hypoxia, hypotension, acidosis, hypokalaemia

ü  Give sodium bicarbonate.

Hypotension: Give intravenous fluids

ü  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.