How to manage Tricyclic antidepressants drug poisoning...

TRICYCLIC ANTIDEPRESSANTS (TCAs)POISONING

 

Introduction

This are agents that act by increasing levels of serotonin and norepinephrine, and acetylcholine action blockade(hence the name tricyclic). in this manner of action in CNS, TCAs is able to cause depression.

Clinical Manifestations

Has anticholinergic effects mydriasis Fever, urinary retention, dry mouth, and ileus.

Systemic effects

CNS: Agitation, drowsiness,convulsion, confusion and coma

Respiratory: Resp depression

Cardiovascular: hypotension, Sinus tachycardia and complex arrhythmias

Management

• No specific antidote is known.

• administer activated charcoal 1-2 g/kg/dose 4-8hrly.

• Careful monitoring patient’s ECG continuously is required. If there’s no hypotension, QRS prolonged/widened, abnormal cardiac conduction, altered level of consciousness or seizures within 6hrs; better outcome is most likely.

• Rx should be started for wide complex arrythmias and prolonged QRS: QRS > 100ms (seizures) and QRS >160ms (arrhythymia).

• Rx metabolic acidosis. Administer bicarbonate (1-2mmol/kg) to maintain pH 7.45 – 7.55 when QRS is widened or in the face of ventricular arrhthymias.

Admin. of NaHCO3 is targeted to narrow QRS and is titrated accordingly by infusion or by bolus.(Lookout for hypokalemia and treat accordingly)

• For Convulsions Rx with benzodiazepines.

• Propranolol is best to Rx arrhythmias that is life-threatening.

• Give  MgSO4 if torsades de pointes occurs.

• Use Norepinephrine and epinephrine to Rx hypotension.

CAUTION!

•   Dopamine is not effective.

• Either Haemodiaysis/Peritoneal dialysis proves not to be effective(tricyclics are protein bound).

• flumazenil common used antidote; it is of importance to avoid its use, for reversal of co-ingestion of benzodiazepines as it can agreviate/induce tricyclic induced seizure activity.