Lithium

Function

Lithium is a mood stabilizer primarily used for the long-term treatment of bipolar disorder. Because lithium has a very 'narrow therapeutic window'—meaning the difference between a therapeutic dose and a toxic dose is small—regular monitoring of serum levels is mandatory. It acts on the central nervous system, though its exact mechanism involves modulating neurotransmitters like glutamate and interfering with intracellular signaling pathways.

Why it is Ordered

This test is ordered to ensure the patient is receiving a dose that is high enough to be effective but low enough to avoid toxicity. Monitoring is most frequent when starting the medication or changing doses. It is also ordered if a patient shows signs of toxicity (confusion, tremors) or if they have developed kidney issues, as lithium is cleared entirely by the kidneys.

Associated Conditions

• Bipolar Disorder: Used to prevent both manic and depressive episodes.
• Major Depressive Disorder: Sometimes used as an augmenting agent when standard antidepressants fail.
• Lithium Toxicity: Occurs when levels exceed 1.5 mmol/L, leading to neurological and renal complications.
• Diabetes Insipidus: A potential side effect of long-term lithium use where the kidneys cannot concentrate urine.