What is the interaction between lithium and ACE inhibitors?

What is the interaction between lithium and ACE inhibitors?

• A. Increased risk of lithium toxicity related to increased urination from ACE inhibitors
• B. ACE inhibitors increase lithium clearance
• C. No interaction
• D. ACE inhibitors prevent lithium toxicity

Answer: (A)

Lithium toxicity risk when combined with ACE inhibitors comes from reduced renal clearance of lithium. Lithium is eliminated by the kidneys and its level in the blood rises if the kidneys aren’t filtering it as well. ACE inhibitors cause dilation of the efferent arterioles, which lowers intraglomerular pressure and can modestly reduce glomerular filtration rate. In someone taking lithium, this reduction in clearance means more lithium stays in the blood, increasing the chance of toxicity. This interaction is more likely in older adults or those with existing kidney impairment, so monitoring lithium levels after starting an ACE inhibitor and adjusting the lithium dose if needed is important. The idea that the interaction happens from increased urination isn’t the mechanism; diuresis isn’t the primary driver of lithium toxicity here.

Lithium toxicity risk when combined with ACE inhibitors comes from reduced renal clearance of lithium. Lithium is eliminated by the kidneys and its level in the blood rises if the kidneys aren’t filtering it as well. ACE inhibitors cause dilation of the efferent arterioles, which lowers intraglomerular pressure and can modestly reduce glomerular filtration rate. In someone taking lithium, this reduction in clearance means more lithium stays in the blood, increasing the chance of toxicity. This interaction is more likely in older adults or those with existing kidney impairment, so monitoring lithium levels after starting an ACE inhibitor and adjusting the lithium dose if needed is important. The idea that the interaction happens from increased urination isn’t the mechanism; diuresis isn’t the primary driver of lithium toxicity here.