What are the treatment and management steps for a patient who accidentally took two doses of Cardizem (diltiazem) 240 mg orally?

Management of Diltiazem 240 mg Double Dose Overdose

For a patient who accidentally took two doses of Cardizem (diltiazem) 240 mg orally, immediate monitoring for cardiovascular effects and supportive care are required, with administration of intravenous calcium if significant hypotension or bradycardia develops.

Initial Assessment and Monitoring

• Immediately establish continuous cardiac monitoring for:

  • Bradycardia
  • Heart block (particularly AV block)
  • Hypotension
  • Signs of cardiac failure

• Obtain baseline vital signs:

  • Blood pressure (watch for hypotension)
  • Heart rate (watch for bradycardia)
  • Respiratory rate
  • Oxygen saturation

• Obtain 12-lead ECG to assess for:

  • PR interval prolongation
  • QRS widening
  • Heart blocks
  • Bradyarrhythmias

• Establish IV access for potential medication administration

Treatment Algorithm

For Asymptomatic Patients (normal vitals, no ECG changes)

1. Continue cardiac monitoring for at least 6-8 hours
2. Consider activated charcoal if presentation is within 1-2 hours of ingestion
3. Maintain IV access
4. Monitor for delayed toxicity (can occur up to 18 hours post-ingestion) 1

For Symptomatic Patients

Bradycardia Management:

1. Administer atropine 0.6-1.0 mg IV 2
2. If no response to atropine, consider:
   • Isoproterenol (cautious administration)
   • Temporary cardiac pacing for persistent bradycardia or high-degree AV block 2, 3

Hypotension Management:

1. Administer intravenous calcium:
   • 1 g calcium chloride or 3 g calcium gluconate over 5 minutes
   • May repeat every 10-20 minutes as necessary
   • For severe cases, consider calcium gluconate continuous infusion at 2 g per hour 2, 1
2. If hypotension persists, administer vasopressors:
   • Dopamine or norepinephrine 2

Cardiac Failure Management:

1. Administer inotropic agents:
   • Isoproterenol, dopamine, or dobutamine
2. Consider diuretics if signs of pulmonary edema 2

Special Considerations

• High-dose calcium therapy: Consider aggressive high-dose IV calcium (up to 13.5 g has been reported) particularly if severe bradycardia or asystole develops 1

• Avoid certain medications:

  • Do not administer additional calcium channel blockers or beta-blockers
  • Avoid medications that may worsen bradycardia or hypotension

• Monitoring duration: Extended monitoring (24 hours) is recommended due to potential for delayed toxicity, especially with sustained-release formulations 1

• Gastrointestinal decontamination: Consider activated charcoal if presentation is within 1-2 hours of ingestion 2

Prognosis

Most patients recover from diltiazem overdose with appropriate supportive care. Fatal outcomes are typically associated with multiple drug ingestions rather than isolated diltiazem overdose 2.

Pitfalls to Avoid

• Underestimating delayed toxicity: Symptoms can worsen 18+ hours after ingestion, particularly with extended-release formulations 1

• Inadequate calcium dosing: In severe cases, higher doses of calcium than typically used may be necessary 1

• Premature discontinuation of monitoring: Continue cardiac monitoring for at least 24 hours due to risk of delayed effects

• Fluid overload: Avoid excessive fluid administration in patients with cardiac dysfunction; vasopressors may be preferable for managing hypotension 4