Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)
Pharmacology
Easy
The normal value of serum lithium test is:
Appeared in: Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)
Explanation
- The standard therapeutic range for serum lithium during maintenance therapy is 0.6 to 1.2 mmol/L (or mEq/L).
- This range is the target for effectively managing conditions like bipolar disorder while minimizing the risk of side effects and toxicity.
- Lithium has a very narrow therapeutic index, meaning the dose required for therapeutic effect is very close to the dose that causes toxicity.
- For monovalent ions like lithium (Li+), 1 mmol/L is equivalent to 1 mEq/L, so the units are interchangeable in this context.
Why Other Options Were Wrong
- Option B: This range is excessively wide and incorrect. A level of 0.10 mmol/L is sub-therapeutic and would not be effective, while a level of 3.2 mmol/L is severely toxic and life-threatening.
- Option C: This range is too high for standard maintenance therapy. Levels approaching 1.5 mmol/L and above (like 1.8 mmol/L) are considered toxic.
- Option D: This entire range is above the standard therapeutic level and falls into the toxic to severely toxic category. Levels above 1.5 mmol/L require immediate medical attention.
Related Visual
Clinical Relevance
- Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Therapeutic drug monitoring for lithium as background academic context rather than a clinical decision trigger.
- Nurses must meticulously monitor patients on lithium for signs of toxicity, such as tremors, nausea, vomiting, and confusion, as the therapeutic window is very narrow.
- Patient education is critical. Nurses should teach patients about the importance of regular blood tests, maintaining consistent salt and fluid intake, and avoiding medications like NSAIDs and diuretics that can increase lithium levels.
- What if? If a patient on lithium presents with a serum level of 1.6 mmol/L and is experiencing coarse hand tremors and confusion, the nurse's priority action is to withhold the next dose of lithium and immediately notify the healthcare provider, as these are clear signs of toxicity.
How to Approach the Question
- First, identify the core of the question, which is asking for the 'normal value' of a serum lithium test. In pharmacology, 'normal' for a drug level refers to the therapeutic range.
- Recall the specific therapeutic range for common medications with narrow therapeutic indexes, like lithium.
- Evaluate the given options. Compare each range to the known standard therapeutic range for lithium maintenance therapy.
- Eliminate options that are too low, too high (toxic), or too broad. The range 0.6-1.2 mmol/L is the standard maintenance level.
Concept Tested & Keywords
- Concept Tested: Therapeutic drug monitoring for lithium.
- Stem keywords: serum lithium test, normal value
- Lead-in keywords: BEST, MOST RELEVANT CLUE
- Negative lead-in flag: false
Question ID
QGeuzIsx7jgL0zmhQbWkR4
Reference Book
E6 Kaplan Sadock's Synopsis of Psychiatry-2022 (pp 1-3768 of 3768) p. 2065-2067
E6 Robert Boland, Marcia L. Verduin - Kaplan and Sadock's Comprehensive Text of Psychiatry-Wolters Kluwer Health (2024) (pp 1-16525 of 16525) pp. 3494-3496, 3495-3497
Practise the full Combined AIIMS - 2020 (Jodhpur, Bhopal, Patna, Raipur)
Attempt every question from this paper in a timed mock, then review the full solution for each one.
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