Which medication is contraindicated when taking lithium?

Diuretics are contraindicated when taking lithium primarily because they can lead to dehydration and an increase in lithium levels in the blood. Lithium is a medication often prescribed for mood stabilization, particularly in conditions like bipolar disorder. Its therapeutic range is narrow, meaning that small changes in dosage or body fluid levels can significantly affect lithium concentration and lead to toxicity.

When a diuretic is used, it can cause the body to excrete more sodium and water, which may lead to a condition called lithium toxicity, characterized by symptoms such as nausea, vomiting, diarrhea, tremors, and even severe neurological effects. Therefore, careful monitoring of sodium and fluid intake is essential when lithium is being administered, and the use of diuretics generally poses risks that can complicate treatment.

In contrast, the other medication categories listed—antidepressants, antipsychotics, and antihistamines—are not inherently contraindicated with lithium, although there could be concerns about interactions or side effects. However, they do not carry the same urgent risk of altering lithium levels as diuretics do.