A nurse is reviewing the list of current medications for a client who is to start a new prescription for carbamazepine.
The nurse should identify which of the following medications interacts with carbamazepine?

Furosemide is a diuretic that is used to treat heart failure by reducing fluid retention and lowering blood pressure. It can cause some side effects, such as increased urination, thirst, dry mouth, headache, dizziness, nausea, and electrolyte imbalance.

Choice A is wrong because BUN (blood urea nitrogen) is a measure of kidney function and a normal range is 7 to 20 mg/dL.

A BUN of 15 mg/dL is not a cause for concern and does not indicate any adverse effect of furosemide.

Choice C is wrong because potassium is an electrolyte that is important for nerve and muscle function and a normal range is 3.5 to 5.0 mEq/L.

Potassium of 3.8 mEq/L is within the normal range and does not indicate any adverse effect of furosemide. However, furosemide can cause low potassium levels (hypokalemia) in some cases, so the nurse should monitor the client’s potassium levels regularly and advise the client to eat foods rich in potassium, such as bananas, oranges, and potatoes.

Choice D is wrong because dizziness upon standing is a common side effect of furosemide and does not require immediate notification of the provider. However, the nurse should instruct the client to rise slowly from a sitting or lying position to prevent falls and to drink enough fluids to prevent dehydration.

Choice B is correct because difficulty hearing or hearing loss is a rare but serious side effect of furosemide that may indicate ototoxicity (damage to the inner ear). This can be irreversible if not treated promptly and may affect the client’s quality of life and safety. The nurse should notify the provider immediately if the client reports difficulty hearing or any other signs of ototoxicity, such as ringing in the ears (tinnitus) or vertigo (a sensation of spinning). The provider may need to adjust the dose of furosemide or switch to another diuretic that is less ototoxic.

Taking a high-ceiling diuretic predisposes this client to developing digoxin toxicity because it can cause hypokalemia (low blood potassium level), which increases the sensitivity of the heart to digoxin. Digoxin is a medicine that is used to treat heart failure or arrhythmias (abnormal heart rhythms) by increasing cardiac contractility and controlling the heart rate. Digoxin toxicity happens when there is too much digoxin in the body and it becomes harmful, causing symptoms such as nausea, vomiting, headache, confusion, vision disturbance, and irregular heartbeat.

Choice A is wrong because taking an HMG CoA reductase inhibitor (also called a statin) does not increase the risk of digoxin toxicity.

Statins are lipid-lowering medications used to prevent coronary heart disease by blocking an enzyme involved in cholesterol synthesis.

Statins do not affect the blood potassium level or the sensitivity of the heart to digoxin.

Choice B is wrong because having a 10-year history of COPD (chronic obstructive pulmonary disease) does not increase the risk of digoxin toxicity. COPD is a lung condition that causes breathing difficulties and chronic inflammation.

COPD does not affect the blood potassium level or the sensitivity of the heart to digoxin.

Choice D is wrong because having a prolapsed mitral valve does not increase the risk of digoxin toxicity.

A prolapsed mitral valve is a condition where the valve between the left atrium and left ventricle of the heart does not close properly, allowing some blood to leak back into the atrium.

A prolapsed mitral valve does not affect the blood potassium level or the sensitivity of the heart to digoxin.