TCAs and NaHCO3

[nothisispatrick]

In Sketchy they say Sodium Bicarbonate is used to treat TCA overdose. One of the reasons they say is because it increases serum pH which favors the non-ionized form of the drug. Why is this? I thought increase serum pH > less H+. Then to compensate for this decrease in H+, wouldn't TCA ionize more to replace to lost H+ ions?

 

[DrStephenStrange]

Sodium bicarbonate also acts as a buffer NaHCO3/HCO3- when administered intravenously. More or less keeping the blood pH around normal level (7.35-7.45). So if the person was in acidosis due to ionized TCA (overdose) and then you give them Sodium bicarb it would raise the pH up to normal and keep it there which is probably around the same level where the drug is at its isoelectric point (neutral).

 

[Oligodinero]

My understanding is sodium bicarbonate is given in TCA overdose to supply Na+ ions to counteract the Na+ blockade effects on the myocardium (manifested by a widened QRS). The bicarbonate does nothing to enhance elimination....it's all about treating the widened QRS and treating acidosis if present.