Can amitriptyline (tricyclic antidepressant) cause hypothermia?

Amitriptyline Can Cause Hypothermia

Yes, amitriptyline can cause hypothermia as a manifestation of overdose or toxicity. According to the FDA drug label, hypothermia is specifically listed as a potential symptom of amitriptyline overdose, alongside other serious conditions including cardiac dysrhythmias, hypotension, CNS depression, and seizures 1.

Mechanisms and Evidence

Amitriptyline's effect on body temperature regulation occurs through several mechanisms:

1. Central nervous system effects: Amitriptyline affects multiple neurotransmitter systems in the brain, particularly those involved in temperature regulation in the hypothalamus.

2. Anticholinergic properties: As a tricyclic antidepressant, amitriptyline has significant anticholinergic effects that can disrupt normal thermoregulation 2.

3. Serotonergic mechanisms: Research suggests that amitriptyline-induced hypothermia may be mediated through serotonergic pathways, as studies have shown correlation between brain 5-HT content and hypothermic response 3.

Clinical Presentation and Recognition

When hypothermia occurs with amitriptyline, it may present alongside other signs of toxicity:

• Core body temperature below 35°C (95°F)
• Altered mental status or CNS depression
• Cardiovascular abnormalities (dysrhythmias, QRS prolongation, hypotension)
• Anticholinergic effects (dilated pupils, dry mucous membranes)
• Muscle rigidity

Management of Amitriptyline-Associated Hypothermia

Management of amitriptyline-induced hypothermia follows these principles:

1. Immediate stabilization:

   • Secure airway, breathing, circulation
   • Initiate cardiac monitoring
   • Establish IV access

2. Temperature management:

   • Active rewarming for significant hypothermia
   • Careful temperature monitoring
   • Avoid rapid rewarming which may precipitate cardiovascular instability

3. Gastrointestinal decontamination (if recent ingestion):

   • Activated charcoal (if appropriate timing and patient can protect airway)
   • Gastric lavage in severe cases

4. Specific interventions for tricyclic overdose:

   • Sodium bicarbonate for QRS prolongation
   • Benzodiazepines for seizures
   • Supportive care for hypotension

Important Considerations

• Hypothermia may not be present immediately but can develop hours after ingestion 4.
• The combination of hypothermia with other signs of tricyclic toxicity indicates significant poisoning and requires aggressive management.
• Poor outcomes (death or neurological sequelae) are associated with prolonged hyperthermia above 40.5°C, but hypothermia can also indicate severe toxicity 4.

Pitfalls to Avoid

1. Delayed recognition: Hypothermia may not be the presenting symptom and can develop later in the course of toxicity.

2. Inadequate monitoring: Patients with suspected amitriptyline toxicity require at least 6 hours of cardiac monitoring, with extended monitoring if signs of toxicity develop 1.

3. Misattribution: Hypothermia in patients taking amitriptyline might be attributed to environmental causes rather than recognized as a toxicity sign.

4. Inadequate gastrointestinal decontamination: This can lead to continued absorption and worsening toxicity.

5. Failure to consult toxicology resources: Poison control centers can provide valuable guidance in managing these complex cases.

For pediatric cases, management principles are similar, but dosing of medications should be adjusted appropriately, and consultation with a poison control center is strongly recommended 1.