TCAs toxicity-treatment

[Estranged]

In First Aid TCAs are listed as weak bases (p.238/2016). However, after a few pages it mentions that NaHCO3 is the treatment of choice in case of toxicity. Is this an error? Shouldn't we acidify the urine?

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[donovank730]

The Bicarb is used for treatment of torsades associated with tca overdose. Not sure if you would acidify the urine for reasons other than that.

 

[68PGunner]

In First Aid TCAs are listed as weak bases (p.238/2016). However, after a few pages it mentions that NaHCO3 is the treatment of choice in case of toxicity. Is this an error? Shouldn't we acidify the urine?

I don't know the actual mechanism but NaHCO3 is used to treat the metabolic acidosis associated w/ TCA overdose.

 

[Fewa Fibroblast]

NaHco3 is used in TCA toxicity in order to prevent/revrese cardotoxicity by increasing the extracellular sodium.
Although TCA is a weak base, NaHco3 here is not used to clear it in uriine.
It is the Na part that is helpful here.

 

[Rahas]

TCA overdose produces cardiotoxicity by binding to and interfering with the action of the fast Na channels. With ECG changes or arrhythmias, the goal is to immediately control these, rather than enhancing urinary clearance.

NaHCO3 accomplishes this in two ways:
1.It alkalinizes the patients serum -> TCA being a base means more of it now shifts to the uncharged form. Since its the charged form that binds the fast Na channel, this decreases its cardiotoxic effects.
2.It increases ECF Na concentration -> increases Na can now better compete with TCAs for binding the fast Na channel