Which treatment mitigates cardiac toxicity from tricyclic antidepressants?

• A. Sodium bicarbonate IV and IV fluids
• B. Calcium gluconate IV
• C. Potassium chloride infusion
• D. Epinephrine infusion

Answer: (A)

Overdose with tricyclic antidepressants blocks fast sodium channels in the heart, causing slowed conduction, widened QRS, and hypotension. The best initial treatment is intraven­ous sodium bicarbonate with IV fluids. The bicarbonate raises serum pH (alkalinization) and provides a larger extracellular sodium load. The extra sodium helps overcome the sodium-channel blockade and improves conduction, while alkalinization reduces the drug’s ability to enter cardiac tissue by shifting it toward a less active form. This combination tends to narrow the QRS and stabilize both rhythm and blood pressure. Other options like calcium gluconate, potassium, or epinephrine do not specifically reverse the sodium-channel blockade and are not the preferred first-line therapy in this scenario.