Pharmacology Quiz: Lab Monitoring For Medications

A 72-year-old female with heart failure (HFrEF) and chronic kidney disease (stage 3, baseline SCr 1.4 mg/dL) is initiated on lisinopril 5 mg daily. Two weeks later, repeat labs are drawn. Results: sodium 138 mEq/L, potassium 5.2 mEq/L, BUN 28 mg/dL, serum creatinine (SCr) 1.7 mg/dL.

Which is the best interpretation of these lab results in the context of her new medication?

An 80-year-old female with a history of heart failure and atrial fibrillation is managed with digoxin 0.125 mg daily and furosemide. She presents with nausea, vomiting, and visual disturbances (yellow halos). Her serum creatinine has increased from 1.1 mg/dL to 1.9 mg/dL over the past six months.

In addition to a serum digoxin level, which lab value is most critical to assess to evaluate the risk and severity of digoxin toxicity in this patient?

An 81-year-old female is started on carbamazepine for trigeminal neuralgia. Two weeks later, her family brings her to the clinic because she has become increasingly lethargic and disoriented. She has no fever or focal neurological deficits.

Which single laboratory test is most crucial to emergently evaluate for a common adverse effect of her new medication?

A patient is started on hydrochlorothiazide 25 mg daily for uncomplicated hypertension. After four weeks of therapy, which of the following patterns of change in laboratory values is most consistent with the known metabolic effects of this drug?

A 59-year-old patient with type 2 diabetes and hypertension is treated with metformin. His renal function has been progressively declining. His physician is reviewing his latest lab results to determine if metformin remains safe.

According to current FDA guidelines, at what estimated glomerular filtration rate (eGFR) is initiating metformin therapy contraindicated and continuation of therapy should be re-evaluated?

A patient stabilized on lithium for bipolar disorder was recently started on hydrochlorothiazide for hypertension. He now presents with tremor, confusion, and ataxia. Lab results show a serum sodium of 128 mEq/L and a lithium level of 2.1 mEq/L (therapeutic range 0.6-1.2 mEq/L).

What is the most accurate explanation for the patient's presentation and lab findings?

A 58-year-old kidney transplant recipient, stable for two years post-transplant, presents for routine labs. His medications include tacrolimus, mycophenolate, and prednisone. The results show a serum creatinine of 1.9 mg/dL (baseline 1.3 mg/dL) and a potassium of 5.8 mEq/L (baseline 4.2 mEq/L). His tacrolimus trough level is 11 ng/mL (target 5-10 ng/mL).

What is the most probable cause of the new lab abnormalities?

A patient with cryptococcal meningitis is being treated with conventional amphotericin B deoxycholate. On the fifth day of treatment, the patient develops premature ventricular contractions (PVCs) noted on telemetry.

In addition to monitoring for nephrotoxicity via BUN and creatinine, which two electrolyte disturbances are the most likely contributors to this arrhythmia?

A 62-year-old female with osteoarthritis and stable heart failure is managed with lisinopril and furosemide. Due to worsening knee pain, her primary care provider prescribes ibuprofen 800 mg three times daily. Two weeks later, she presents with increased shortness of breath and a 5 kg weight gain.

Which combination of lab abnormalities is most likely to be found, explaining her clinical deterioration?

A 62-year-old male with a mechanical mitral valve is on warfarin. His target INR range is 2.5 to 3.5. A routine check shows an INR of 2.2. He reports perfect adherence, no new medications, and no significant dietary changes. He is asymptomatic.

What is the most appropriate adjustment to his therapy?

A 75-year-old male (70 kg) with a new diagnosis of osteomyelitis requires treatment with an aminoglycoside. His serum creatinine is stable at 1.8 mg/dL. The pharmacist calculates his creatinine clearance (CrCl) using the Cockcroft-Gault equation to be approximately 35 mL/min. The hospital's standard dosing protocol calls for a dose reduction for this drug when CrCl is less than 50 mL/min.

Based on this interpretation of the patient's renal function, what is the most appropriate next step?

An 82-year-old male with heart failure and hypertension is taking lisinopril 20 mg daily and spironolactone 25 mg daily. He develops a complicated urinary tract infection and is prescribed a 10-day course of trimethoprim-sulfamethoxazole. He now presents to the emergency department with generalized weakness and palpitations.

An ECG is performed. Which acute electrolyte abnormality is the most likely underlying cause of his symptoms?

A 68-year-old male with atrial fibrillation maintained on warfarin (target INR 2.0-3.0) is diagnosed with a urinary tract infection. He is prescribed a 7-day course of trimethoprim-sulfamethoxazole. Five days later, a routine check shows his INR is 4.8. He reports no bleeding or bruising.

What is the most appropriate immediate action regarding his warfarin therapy?

A 65-year-old male with decompensated heart failure is receiving high-dose intravenous furosemide. He develops significant muscle weakness and cramping. An ECG shows flattened T-waves and the presence of U-waves. His latest lab results are: Potassium 2.8 mEq/L, Magnesium 1.3 mg/dL, Sodium 135 mEq/L, Calcium 9.1 mg/dL.

Given the clinical presentation and ECG findings, which lab abnormality should be prioritized for correction to prevent life-threatening arrhythmias?

A 55-year-old male with cirrhosis and ascites is managed with furosemide 80 mg daily and spironolactone 200 mg daily. He presents for a routine follow-up. His lab results are: sodium 132 mEq/L, potassium 5.9 mEq/L, BUN 35 mg/dL, creatinine 1.4 mg/dL.

Which medication is the most likely contributor to his hyperkalemia?

A 62-year-old female with osteoarthritis and stable heart failure is managed with lisinopril and furosemide. Due to worsening knee pain, her primary care provider prescribes ibuprofen 800 mg three times daily. Two weeks later, she presents with increased shortness of breath and a 5 kg weight gain.

Which combination of lab abnormalities is most likely to be found, explaining her clinical deterioration?

A patient with cryptococcal meningitis is being treated with conventional amphotericin B deoxycholate. On the fifth day of treatment, the patient develops premature ventricular contractions (PVCs) noted on telemetry.

In addition to monitoring for nephrotoxicity via BUN and creatinine, which two electrolyte disturbances are the most likely contributors to this arrhythmia?

A patient with a history of DVT is on apixaban. A review of their lab trends reveals the following: Baseline SCr: 0.9 mg/dL; 6 months: 1.2 mg/dL; 12 months: 1.6 mg/dL. What is the most significant clinical concern related to this trend and their anticoagulant therapy?

An 81-year-old female is started on carbamazepine for trigeminal neuralgia. Two weeks later, her family brings her to the clinic because she has become increasingly lethargic and disoriented. She has no fever or focal neurological deficits.

Which single laboratory test is most crucial to emergently evaluate for a common adverse effect of her new medication?

A 78-year-old male with non-valvular atrial fibrillation requires anticoagulation. His medical history includes severe chronic kidney disease with a calculated creatinine clearance of 25 mL/min. His physician is considering treatment options.

For which of the following anticoagulants is the interpretation of his renal function labs most critical for determining if the drug can be used at all?