Question

For 12 years, a 65 year old patient with bipolar affective disorder has been treated with lithium 900 mg daily. When oral HCTC 12.5 daily is added for hypertension, the patient develops nausea, vomiting, ataxia, and muscle weakness and the patient's serum lithium level is 2.0. The interaction of the lithium and the thiazide diuretic has induced:

a. hypokalemia
b. hyponatremia
c. Increased renal clearance of lithium
d. Decreased renal clearance of lithium

Answer 1

Adding a thiazide diuretic like HCTZ to a patient's regimen of lithium can lead to decreased renal clearance of lithium, potentially causing lithium toxicity and related symptoms.

Step-by-step explanation:

When thiazide diuretics like hydrochlorothiazide (HCTZ) are taken concurrently with lithium, they can lead to a decreased renal clearance of lithium, causing increased serum levels, which can result in symptoms of lithium toxicity. This interaction occurs because thiazides decrease the elimination of lithium by the kidneys, causing lithium to accumulate in the body. Symptoms of lithium toxicity include nausea, vomiting, ataxia, and muscle weakness, as mentioned for the patient with a serum lithium level of 2.0. It is vital for healthcare providers to monitor lithium levels closely when starting or adjusting diuretic therapy in patients on lithium.