Question 1

A 38-year-old woman with bipolar I disorder has been stable on lithium 900mg daily for two years (level 0.8 mEq/L). She presents with nausea, coarse tremor, and unsteady gait. She reports starting ibuprofen 600mg three times daily for knee pain one week ago. What is the most likely explanation?

Accepted Answer

NSAIDs reduce renal blood flow and increase proximal tubule reabsorption of lithium, raising serum levels. A patient stable for years can become toxic within days of starting an NSAID. Her symptoms (nausea, coarse tremor, and ataxia) are consistent with moderate lithium toxicity. The immediate steps are to check a STAT lithium level, hold the lithium, discontinue the ibuprofen, and ensure adequate hydration. This is one of the most common and preventable causes of lithium toxicity, and it underscores why patients on lithium need to be educated about OTC medication risks.

Question 2

You are choosing between lithium and valproate for a 32-year-old man with bipolar I disorder who has had three manic episodes and one serious suicide attempt. He has no medical comorbidities and no substance use. Which factor most strongly favors lithium in this case?

Accepted Answer

In a patient with significant suicide risk, lithium's anti-suicide evidence is a clinically meaningful differentiator. Both lithium and valproate are effective for mania, and lithium's therapeutic window is actually narrower (making answer B incorrect). Lithium is not "safer" or "easier" than valproate; it requires more monitoring and has its own side effect burden. But the anti-suicide data is unique to lithium and is strong enough to influence the choice when suicide risk is a primary concern. This is a case where the harder-to-manage medication is the right one.

Question 3

A 55-year-old man on lithium 1200mg daily (level 1.0 mEq/L) has his annual lab work. His TSH is 8.2 mIU/L (elevated) and free T4 is 0.7 ng/dL (low-normal). He feels well psychiatrically and reports no symptoms of hypothyroidism. What is the most appropriate next step?

Accepted Answer

Lithium-induced hypothyroidism is common and manageable. The appropriate response is not to stop an effective mood stabilizer; it is to supplement with levothyroxine and continue lithium. His TSH of 8.2 is elevated enough to warrant treatment even in the absence of symptoms (TSH in this range is commonly treated, especially with an ongoing cause like lithium and a long-term plan to continue it, because it is predictable and easily managed with supplementation). Reducing the lithium dose (answer B) might lower the TSH slightly but risks destabilizing his psychiatric condition. Discontinuing lithium (answer A) is an overreaction to a treatable side effect. This scenario is extremely common in long-term lithium management.

Lithium

Side Effects Worth Knowing

Fine Tremor: usually hands, dose-dependent

GI Effects: nausea, diarrhea, abdominal discomfort

Polyuria and Polydipsia: increased urination and thirst

Hypothyroidism: elevated TSH, sometimes clinical symptoms

Renal Effects: chronic kidney disease risk with long-term use

Weight Gain: moderate, less than valproate or olanzapine

Cardiac Effects: ECG changes, primarily T-wave flattening

Teratogenicity: Ebstein's anomaly risk, lower than historically believed

See This Medication in Action

References & Further Reading