Sodium bicarbonate is a buffering agent that reacts with hydrogen ions to correct acidemia and produce alkalemia. Urinary alkalinization from renally excreted bicarbonate ions enhances the renal elimination of certain acidic drugs (eg, salicylate, chlorpropamide, chlorophenoxy herbicides, fluoride, and phenobarbital); it also may help to prevent renal tubular damage from deposition of myoglobin in patients with rhabdomyolysis and from precipitation (by enhancing solubility) of methotrexate in patients undergoing high-dose therapy. In addition, maintenance of a normal or high serum pH may prevent intracellular distribution of salicylate and formate (a toxic metabolite of methanol).
The sodium ion load and alkalemia produced by hypertonic sodium bicarbonate reverse the sodium channel–dependent membrane-depressant (“quinidine-like”) effects of several drugs (eg, tricyclic antidepressants, type Ia and type Ic antiarrhythmic agents, propranolol, propoxyphene, cocaine, bupropion, diphenhydramine) and of yew berries (Taxus cuspidata).
Alkalinization causes an intracellular shift of potassium and is used for the acute treatment of hyperkalemia.
Sodium bicarbonate given orally or by gastric lavage forms an insoluble salt with iron and theoretically may help prevent absorption of ingested iron tablets (unproven).
Neutralization of acidic substances to prevent caustic injury usually is not recommended because of the potential for an exothermic reaction, generation of gas, and lack of evidence that tissue injury is minimized. Nebulized sodium bicarbonate has been used to neutralize the hydrochloric acid formed on mucosal surfaces from chlorine gas exposures (efficacy uncertain).
Early animal studies and human case series of organophosphate (OP) poisonings in regions lacking sufficient access to traditional antidotes (oximes, atropine) have suggested beneficial outcomes from high-dose IV bicarbonate therapy (5 mEq/kg over 60 minutes, then 5–6 mEq/kg/d). The authors of those studies theorize that alkalinization may enhance degradation or elimination of OPs, improve tissue perfusion with volume expansion, and enhance the efficacy of 2-PAM. Systematic reviews of human trials have failed to show differences in mortality but have demonstrated a trend toward improved outcomes (lower atropine requirements and shorter length of hospital stay).