SAQ 238 – Toxicology – sustained-release verapamil overdose

Question 9. sustained-release verapamil overdose.

a. Historical factors

• Co-ingestants and access to other cardiotoxic medications.
• Cardiac comorbidities.
• Suicidality, including circumstances and current attitude.

b. Initial risk assessment

• Life-threatening toxicity is expected after more than ten tablets.
• Onset may be delayed for up to 16 hours with sustained-release tablets.
• Aggressive decontamination may reduce toxicity.
• Risk increases with cardiotoxic co-ingestants or pre-existing cardiac disease.

c. Mainstay of therapy

• High-dose insulin euglycaemia therapy.

d. Indication

• Commence as soon as significant toxicity appears, such as fluid-resistant hypotension or cardiac dysrhythmia.

e. Other antidotal therapy

• IV calcium, which may temporarily improve heart rate and blood pressure.

f. Revised risk assessment

• Current haemodynamics do not yet indicate calcium-channel-blocker toxicity.
• Reduced GCS suggests a co-ingestant because it is not typical of isolated calcium-channel-blocker toxicity.
• A cardiotoxic co-ingestant would increase risk.

g. Activated charcoal

• Should have been given on arrival while GCS was 15 and the patient cooperative.
• Effective within four hours for sustained-release verapamil.
• With the current reduced GCS, intubate before charcoal administration.

h. Other modalities

• Whole-bowel irrigation.
• Ventricular pacing.
• Cardiopulmonary bypass.
• ECMO.
• Intra-aortic balloon pump.