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BTSC Staff Nurse 1 August-2025
Pharmacology
Easy

Which of the following mood stabilizers requires regular serum level monitoring to prevent toxicity?

Appeared in: BTSC Staff Nurse 1 August-2025

Explanation

  • Lithium has a very narrow therapeutic index, which means the difference between a therapeutic dose and a toxic dose is small.
  • Regular monitoring of serum levels (typically every 3-6 months during maintenance) is essential to prevent toxicity.
  • The therapeutic range for maintenance is generally 0.6-1.2 mEq/L.
  • Signs of toxicity can appear at levels just above this range (greater than 1.2 mEq/L) and can lead to severe neurological, renal, and cardiac complications, and even death.

Why Other Options Were Wrong

  • Option A: Routine serum level monitoring for lamotrigine is not standard practice because a clear therapeutic range has not been established. Dosing is titrated slowly based on the patient's clinical response and to minimize the risk of a severe rash (Stevens-Johnson Syndrome).
  • Option B: While serum levels of carbamazepine are monitored to ensure efficacy and avoid toxicity (target range 4-12 mcg/mL), the requirement is not as strict or as universally critical as it is for lithium. Monitoring is also important because carbamazepine induces its own metabolism over time.
  • Option C: Valproate serum levels are often monitored (therapeutic range 50-125 mcg/mL) to optimize the dose and check for adherence. However, the primary safety monitoring for valproate often focuses on liver function tests and complete blood counts due to risks of hepatotoxicity and thrombocytopenia.

Related Visual

Visual explanation — Related Visual
Clinical Relevance
  • Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacotherapy for Bipolar Disorder and Serum Drug Monitoring as background academic context rather than a clinical decision trigger.
  • Nurses play a critical role in educating patients about the absolute necessity of adhering to lithium therapy and attending all scheduled blood test appointments.
  • A key nursing responsibility is to teach patients and their families to recognize and immediately report early signs of lithium toxicity, such as worsening tremors, nausea, vomiting, diarrhea, and confusion.
  • Patient education must include the importance of maintaining stable fluid and salt intake, as dehydration or hyponatremia can quickly lead to toxic lithium levels.
How to Approach the Question
  • This is a factual recall question testing your knowledge of psychopharmacology.
  • First, identify the keywords in the question: 'mood stabilizer', 'requires regular serum level monitoring', and 'prevent toxicity'.
  • Think about the specific safety profiles of each drug listed in the options.
  • Recall that one of these drugs is famously associated with a 'narrow therapeutic index'. This characteristic is the primary reason for mandatory, regular blood monitoring.
  • Compare the monitoring needs. While levels of valproate and carbamazepine can be checked, lithium is the only one for which regular monitoring is an absolute requirement for safe use.
Concept Tested & Keywords
  • Concept Tested: Pharmacotherapy for Bipolar Disorder and Serum Drug Monitoring
  • Stem keywords: mood stabilizers, serum level monitoring, toxicity
  • Lead-in keywords: Which

Question ID

QkqFXw_EPNc-2DrLEpMP0j

Reference Book

E6 Robert Boland, Marcia L. Verduin - Kaplan and Sadock's Comprehensive Text of Psychiatry-Wolters Kluwer Health (2024) (pp 1-16525 of 16525) pp. 3496-3498, 3494-3496, 5581-5583

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