What is the most appropriate initial intravenous treatment for a patient with tachycardia, hypotension, and an empty bottle of amitriptyline?

In the case of potential amitriptyline overdose, the most appropriate initial intravenous treatment is sodium bicarbonate. Amitriptyline is a tricyclic antidepressant that can cause significant cardiac toxicity, including tachycardia, hypotension, and the risk of life-threatening arrhythmias, primarily due to its anticholinergic properties and effects on cardiac conduction.

Sodium bicarbonate serves multiple purposes in this scenario. It helps to alkalinize the serum, which can counteract the cardiotoxic effects of tricyclic antidepressants. Alkalinization raises the pH and can bind to the drug, promoting its non-ionized form, which is less likely to interact with sodium channels. This can help stabilize cardiac membranes and reduce the risk of arrhythmias in patients who present with QRS widening, a common finding in tricyclic overdoses.

In the context of treating an overdose, the focus is on managing complications and preventing further harm. Sodium bicarbonate has been shown to improve hemodynamics and mitigate depression of cardiac conduction that occurs with such overdoses. This makes it a crucial and appropriate choice in the initial management of a patient exhibiting symptoms indicative of amitriptyline toxicity.