MTM Drug Therapy Monitoring & Clinical Decision-Making 3 — Questions and Answers
Question 1: A patient with heart failure (EF 35%) is started on carvedilol. Which clinical response would indicate the drug should be titrated up sooner than planned?
- Heart rate decreased from 88 to 72 bpm
- Blood pressure dropped from 130/80 to 100/65 mmHg
- Patient reports improved dyspnea on exertion at 2 weeks (Correct answer)
- Peripheral edema worsened at week 1
Correct answer: Patient reports improved dyspnea on exertion at 2 weeks
Symptomatic improvement such as reduced dyspnea indicates the patient is tolerating beta-blockade well and supports dose uptitration.
Question 2: Which therapeutic drug monitoring parameter is MOST clinically relevant for vancomycin in treating MRSA bacteremia?
- Peak serum concentration >40 mg/L
- Trough serum concentration 15-20 mg/L
- AUC24/MIC ratio of 400-600 mg·h/L (Correct answer)
- Half-life less than 6 hours
Correct answer: AUC24/MIC ratio of 400-600 mg·h/L
Current ASHP/IDSA/SIDP guidelines recommend AUC24/MIC-guided vancomycin dosing (400-600) over trough-only monitoring for MRSA infections.
Question 3: A patient's tacrolimus trough is 3.2 ng/mL at 6 months post-kidney transplant (target 5-10 ng/mL). After ruling out non-adherence, what is the most likely cause of subtherapeutic levels?
- New prescription of ketoconazole
- Recent initiation of rifampin (Correct answer)
- Addition of diltiazem
- Co-administration of fluconazole
Correct answer: Recent initiation of rifampin
Rifampin is a potent CYP3A4 and P-glycoprotein inducer that can reduce tacrolimus levels by up to 90%, leading to rejection risk.
Question 4: In a patient with stage 4 CKD (eGFR 22 mL/min/1.73m²) and type 2 diabetes, which glucose-lowering agent requires the most significant dose adjustment?
- Insulin glargine
- Empagliflozin
- Metformin (Correct answer)
- Dulaglutide
Correct answer: Metformin
Metformin is contraindicated when eGFR falls below 30 mL/min/1.73m² due to risk of lactic acidosis from drug accumulation.
Question 5: Which monitoring frequency is appropriate for patients on long-term oral corticosteroids to screen for a common metabolic complication?
- Fasting glucose at baseline and every 3 months (Correct answer)
- Lipid panel every 2 years
- Serum calcium monthly
- Thyroid function tests every 6 months
Correct answer: Fasting glucose at baseline and every 3 months
Corticosteroids cause gluconeogenesis and insulin resistance, making quarterly fasting glucose monitoring essential to detect steroid-induced hyperglycemia.
Question 6: A patient on phenytoin for epilepsy has a total phenytoin level of 8 mcg/mL with albumin of 2.1 g/dL. What does this result indicate?
- Subtherapeutic phenytoin requiring immediate dose increase
- Likely therapeutic free phenytoin level despite low total (Correct answer)
- Toxic phenytoin level requiring dose reduction
- Lab error that should be repeated
Correct answer: Likely therapeutic free phenytoin level despite low total
Using the Sheiner-Tozer equation, corrected phenytoin = 8/(0.2×2.1 + 0.1) ≈ 16 mcg/mL, suggesting adequate free drug levels despite low albumin.
Question 7: When assessing adherence in a patient with poorly controlled hypertension, which objective measure provides the most reliable verification?
- Patient self-report diary
- Pill count at clinic visit
- Pharmacy refill records over 6 months (Correct answer)
- Urine drug screening for antihypertensive metabolites
Correct answer: Pharmacy refill records over 6 months
Pharmacy refill records (medication possession ratio) provide an objective, longitudinal measure of adherence that is less subject to white-coat bias than clinic-based assessments.
MTM Drug Therapy Monitoring & Clinical Decision-Making 3
A patient with heart failure (EF 35%) is started on carvedilol.
Which clinical response would indicate the drug should be titrated up sooner than planned?