What is the effect of low sodium levels on lithium?

Low sodium levels can significantly affect the metabolism and excretion of lithium in the body. When sodium levels are low, the renal (kidney) handling of lithium changes. The kidneys may retain lithium in an effort to maintain sodium balance, which leads to an increased concentration of lithium in the blood. This process ultimately prolongs lithium’s half-life, as the body holds onto the medication longer when sodium is deficient.

This physiological mechanism is particularly important to understand in the context of patients who are on lithium therapy, as low sodium can lead to potential toxicity from lithium accumulation. Monitoring serum sodium levels is crucial for individuals under lithium treatment to ensure safe therapeutic levels are maintained and to avoid adverse effects.