1. Tricyclic antidepressants (TCA)
Objective
Understand metabolism of cyclic antidepressants overdose.
Master the clinical presentation of TCA toxicity.
Aware of TCA toxicity management.
Use of HCO3 in TCA and managing its side effects.
Zohair Al Aseri MD,FRCPC EM & CCM

2. Antidepressants PERSPECTIVE Including cyclic antidepressants (CAs),
selective serotonin reuptake inhibitors (SSRIs),
monoamine oxidase inhibitors (MAOIs)
and miscellaneous agents.
Antidepressants can be classified based on structure or major mechanism of action.
Zohair Al Aseri MD,FRCPC EM & CCM

3. CYCLIC ANTIDEPRESSANTS
Principles of Disease
Tricyclic antidepressant TCAs and the tetracyclic antidepressant have similar properties and are called CAs.
well absorbed from the GI tract
Peak plasma concentrations in 2 to 4 hs after therapeutic doses are reached.
Absorption is prolonged in overdose
Zohair Al Aseri MD,FRCPC EM & CCM

4. Principles of Disease
So 6-hour observation period in management of CA overdose is appropriate
CAs are highly lipophilic
Extensively bound to plasma proteins
Large volumes of distribution.
CAs are metabolized predominantly by the liver.
Zohair Al Aseri MD,FRCPC EM & CCM 4

5. MAJOR PHARMACODYNAMIC EFFECTS OF CYCLIC ANTIDEPRESSANTS
Zohair Al Aseri MD,FRCPC EM & CCM

6. PERIPHERAL NERVOUS SYSTEM EFFECTS OF CYCLIC ANTIDEPRESSANTS
Zohair Al Aseri MD,FRCPC EM & CCM

7. CENTRAL NERVOUS SYSTEM EFFECTS OF CYCLIC ANTIDEPRESSANTS
Zohair Al Aseri MD,FRCPC EM & CCM

8. Clinical Features
TCA toxicity should be considered in all patients with a decreased level of consciousness and prolonged QRS complex.
Zohair Al Aseri MD,FRCPC EM & CCM

9. Diagnostic Strategies
A dose greater than 10 mg/kg or 1000 mg in an adult should be considered life-threatening.
Suspect CA poisoning in the following
Patients who have an anticholinergic toxidrome
Decreased level of consciousness,
QRS prolongation (>100 msec)
Rightward deviation of the terminal 40-msec QRS axis (R wave in aVR > 3 mm or R/SaVR ratio of >0.7)
Zohair Al Aseri MD,FRCPC EM & CCM

10. Zohair Al Aseri MD,FRCPC EM & CCM

11. A ECG ventricular bigeminy, right axis deviation, wide QRS complex, long QTcinterval, and right deviation of terminal 40-msecQRS vector in limb leads,with prominent R wave in aVR.
B,ECG of same patient after receiving bolus and continuous intravenous infusion of sodium bicarbonate shows sinus tachycardia, 90-degree axis, slight prolongation of QRS and QTc intervals, and persistent right axis deviation of terminal 40 msec in limb leads.
C,ECG of same patient 25 hours after ingestion and 4 hours after termination of sodium bicarbonate infusion shows persistent but improved sinus tachycardia, normalization ofQRS axis and width, normalization of QTc interval, and resolution of prominent R wave in aVR.
Zohair Al Aseri MD,FRCPC EM & CCM

12. TCA levels
Neither serum toxicology tests nor laboratory tests are useful for clinical decision-making.
Diagnosis, treatment, and disposition should be based on a clinical basis and with ECG and cardiac monitoring.
Zohair Al Aseri MD,FRCPC EM & CCM

13. TCA Overdose Management
CAB
Endotracheal intubation for low level of consciousness.
Zohair Al Aseri MD,FRCPC EM & CCM

14. TCA Overdose Management
Gastric lavage & activated charcoal
Within 60 minutes from time of ingestion
Lethal amount
Airway protection
NO physostigmine in TCA Overdose, as it will cause
Seizures
Cardiac arrest
Zohair Al Aseri MD,FRCPC EM & CCM

15. TCA Overdose Management
Hypertension…………no treatment.
Hypotension start with isotonic crystalloids.
Sodium bicarbonate (NaHCO3)
If QRS greater than 100 msec, awith hypotension or a dysrhythmia, or if the patient is acidemic,.
If hypotension does not resolve, norepinephrine or dopamine is recommended. (high-dose)
Seizures
Usually respond to IV lorazepam or diazepam.
Zohair Al Aseri MD,FRCPC EM & CCM

16. Algorithm for management of cyclic antidepressant overdose
Algorithm for management of cyclic antidepressant overdose. (Modified from Cyclic antidepressant (CA) overdose. In Callaham M [ed]: Current Therapy in Emergency Medicine. Philadelphia, BC Decker, 1991.)
Zohair Al Aseri MD,FRCPC EM & CCM

17. TCA Overdose Management
Flumazenil is contraindicated, even if benzodiazepines are known coingestants.
Flumazenil counteracts the anticonvulsant activity of the co-ingested benzodiazepines.
Phenytoin is contraindicated in TCA Seizures.
Zohair Al Aseri MD,FRCPC EM & CCM

18. TCA Overdose Management
TCA induced Hyperthermia
Best treated with control of seizures and neuromuscular blockade.
A nondepolarizing neuromuscular blocker (e.g., rocuronium) is recommended if rhabdomyolysis and high K with ECG changes are present.
Evaporative cooling should be used until core temperature reaches 38.5? C.
Zohair Al Aseri MD,FRCPC EM & CCM

19. Disposition 6 hours of observation
Patients may be discharged for psychiatric evaluation if they do not develop
(1) Desaturation
(2) QRS greater than 100 msec
(3) sinus tachycardia
(4) dysrhythmias
(5) hypotension
(6) decreased level of consciousness
(7) seizures
(8) abnormal or inactive bowel sounds.
Zohair Al Aseri MD,FRCPC EM & CCM