Lithium Toxicity: Therapeutic Use, Toxicity and Interactions

Lithium toxicity is a classic exam topic because lithium is effective but unforgiving. It is used for long-term treatment of bipolar disorder and has a narrow therapeutic range. Questions usually ask about monitoring, interacting drugs or the right response to a patient who looks toxic.

Use and monitoring

Lithium is used to prevent mood episodes in bipolar disorder and as an augmentation agent in some depression. Before and during treatment, monitor kidney function, thyroid function, calcium and the serum lithium level, usually about twelve hours after the last dose. A typical maintenance range is narrow, so follow local guidance.

Common adverse effects

• Fine tremor
• Polyuria and polydipsia from nephrogenic diabetes insipidus
• Hypothyroidism
• Weight gain
• Hyperparathyroidism with raised calcium
• Teratogenicity, including a risk of cardiac malformations

Interacting drugs

Lithium is cleared by the kidneys, so anything that reduces its excretion can cause toxicity. Remember:

• Thiazide diuretics
• Non-steroidal anti-inflammatory drugs
• ACE inhibitors and angiotensin receptor blockers

Dehydration, vomiting, diarrhea, low sodium intake and kidney injury have the same effect.

Signs of toxicity

Early signs include nausea, vomiting, diarrhea, coarse tremor and unsteadiness. Moderate to severe toxicity causes confusion, ataxia, myoclonus, seizures, arrhythmias and coma.

Management of toxicity

Stop lithium, check the level and kidney function, and give intravenous fluids to restore hydration and promote elimination, usually with isotonic saline. Do not use diuretics to try to flush it out. Hemodialysis is considered for severe symptoms, very high levels or reduced kidney function.

Safe prescribing points

Give clear advice to patients about hydration, interacting over-the-counter drugs and the symptoms that need urgent review. Do not stop lithium suddenly without advice because of the risk of relapse.

A classic exam pattern

A patient on lithium starts a thiazide for hypertension and later presents with tremor, vomiting and confusion. The key step is to recognize toxicity, stop the lithium and check the level and kidney function.

Study tips

• Memorize the three interacting drug groups
• Link each adverse effect with a monitoring test
• Review each wrong answer for the safety principle you missed

This article is for exam revision and does not replace current clinical guidelines. Practice psychiatry cases in the Namazj free trial.