Tricyclic and Other Cyclic Antidepressants

Question-and-answer flashcards covering indications, pharmacodynamics, toxicity, diagnosis, and management of tricyclic and other cyclic antidepressant use and overdose.

What are the primary clinical uses of cyclic antidepressants (CAs)?

Depression, neuropathic pain, migraine prophylaxis, obsessive-compulsive disorder, ADHD, and enuresis.

According to the monoamine hypothesis, how do CAs exert antidepressant effects?

By inhibiting the reuptake of norepinephrine, serotonin, and dopamine at CNS nerve terminals.

Which neurotransmitter channel do CAs inhibit that may contribute to seizures?

The γ-aminobutyric acid (GABA) chloride channel.

Name three receptor types blocked by CAs.

Muscarinic cholinergic, histaminic (H1), and α1-adrenergic receptors.

How does sodium channel blockade by CAs relate to their therapeutic use?

It contributes to their efficacy in treating neuropathic pain.

List the classic toxic symptoms seen in severe CA overdose.

Hypotension, dysrhythmias, coma, seizures, and hyperthermia.

What are the primary mechanisms behind CA-induced cardiovascular toxicity?

Effects on the cardiac action potential, negative inotropy, altered vascular tone, and autonomic nervous system effects.

Why are seizures a major concern in CA overdose?

Because CNS toxicity from cholinergic and GABA interference plus sodium channel blockade lowers the seizure threshold.

What neurologic presentation characterized by agitation, disorientation, and delusions is associated with CA anticholinergic effects?

Delirium.

Within what time frame do most deaths from CA overdose occur after hospital arrival?

Within the first 24 hours, often the first few hours.

Which ECG finding is the most useful predictor of serious CA toxicity?

QRS interval prolongation.

A QRS width of ≥100 msec on ECG in a CA overdose indicates what?

Significant sodium channel blockade and need for aggressive treatment such as sodium bicarbonate.

What qualitative laboratory methods can detect CAs in urine?

Thin-layer chromatography or liquid chromatography.

At what serum CA concentration does life-threatening toxicity usually begin?

Above 100 ng/mL.

Describe the initial supportive measures for a suspected CA overdose patient.

Establish IV access, continuous cardiac monitoring, and frequent vital sign checks including temperature.

When should early endotracheal intubation be considered in CA overdose?

In patients with extreme lethargy, agitation, seizures, or dysrhythmias.

What decontamination step is recommended if CA ingestion occurred within 1 hour?

Prompt administration of activated charcoal.

Why is airway protection essential before giving charcoal to a drowsy CA-overdose patient?

To prevent aspiration of charcoal and resulting pulmonary complications.

How does intravenous sodium bicarbonate (NaHCO3) help in CA cardiotoxicity?

Alkalinizes serum, decreasing free CA binding in cardiac cells and provides sodium to overcome Na+ channel blockade.

List standard indications for starting NaHCO3 therapy in CA overdose.

Serum pH

When can a symptomatic CA-overdose patient be discharged from monitoring?

After being symptom-free for at least 24 hours.

In immediate-release CA overdose, what observation period is sufficient for an asymptomatic patient?

6 hours of monitoring (longer if sustained-release formulation involved).