Registered Practical Nurse (RPN) Practice Test

What interaction may occur when a patient taking lithium also uses Captopril?

1. Reduction in lithium levels

2. Increase in serum lithium levels and potential toxicity

3. No significant interaction

4. Increase in blood pressure

The correct answer is: Increase in serum lithium levels and potential toxicity

The interaction that may occur when a patient taking lithium also uses Captopril is characterized by an increase in serum lithium levels and potential toxicity. This occurs because Captopril, an ACE inhibitor, can reduce renal blood flow and affect kidney function, leading to decreased clearance of lithium from the body. When lithium levels rise, there is an increased risk for lithium toxicity, which can manifest as symptoms such as nausea, tremors, confusion, and even more severe neurological symptoms. It is important for healthcare providers to monitor lithium levels closely in patients who start taking Captopril or who have a change in their renal function. This interaction underscores the need for vigilance when prescribing medications that impact renal blood flow or function, especially in patients who are on long-term lithium therapy.