IGNOU PB. Bsc. Nsg. Entrance-2025
Pharmacology
Medium
In Lithium therapy, the serum lithium level is monitored for the first time :
Appeared in: IGNOU PB. Bsc. Nsg. Entrance-2025
Explanation
- Lithium has a half-life of about 24 hours.
- A drug reaches a stable, or 'steady-state', concentration in the blood after approximately 4-5 half-lives.
- For lithium, this means a steady state is achieved in about 4-5 days.
- Therefore, the first blood level is drawn after 3-5 days to ensure the measurement is a reliable indicator of the drug's concentration at that specific dose.
- This allows clinicians to determine if the dose is within the therapeutic range (0.6-1.2 mEq/L) and not approaching toxic levels.
Why Other Options Were Wrong
- Option A: This is too early. At 12-24 hours, lithium has not reached a steady-state concentration, so the blood level would not be a reliable measure for dose adjustment. The 12-hour mark is significant for the timing of the blood draw (12 hours post-dose) once steady state is achieved, not for the initial day of testing.
- Option C: This is still too early. At 36-48 hours (1.5-2 days), the drug has only gone through 1-2 half-lives and has not yet reached a stable concentration in the blood.
- Option D: This is dangerously late for the first check. Lithium has a narrow therapeutic window, and waiting 10-14 days could lead to undetected and potentially severe toxicity if the initial dose was too high for the patient's clearance.
Related Visual
Clinical Relevance
- Nursing practice connection: Knowing Pharmacokinetics and therapeutic drug monitoring of lithium helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
- Lithium has a narrow therapeutic index (0.6-1.2 mEq/L), meaning the dose that is effective is very close to the dose that is toxic. This makes timely and accurate monitoring critical for patient safety.
- Nurses play a key role in educating patients about the importance of consistent dosing, maintaining stable fluid and salt intake, and recognizing early signs of toxicity (e.g., tremors, nausea, diarrhea).
- What if? If a patient on lithium starts taking an NSAID (like ibuprofen) for pain, the nurse must be aware that NSAIDs can decrease renal clearance of lithium, causing lithium levels to rise and increasing the risk of toxicity. The patient should be advised to use an alternative like acetaminophen and to report any new symptoms.
How to Approach the Question
- First, identify the core of the question: it's asking about the timing of the initial drug level monitoring for lithium.
- Recall the key pharmacokinetic principle of 'steady state'. This is the point where a drug's concentration is stable, and it's the correct time to measure therapeutic levels.
- Remember that steady state is typically reached after 4-5 half-lives of a drug.
- Access your knowledge about lithium: its half-life is approximately 24 hours.
- Calculate the time to steady state: 24 hours/half-life × 5 half-lives = 120 hours, which is 5 days.
- Evaluate the options based on this calculation. The '3-5 days' option aligns perfectly with the time required to reach steady state, making it the most logical and safest choice.
Concept Tested & Keywords
- Concept Tested: Pharmacokinetics and therapeutic drug monitoring of lithium.
- Stem keywords: Lithium therapy, serum lithium level, monitored, first time
- Lead-in keywords: first time
- Negative lead-in flag: false
Question ID
QUVa2mDyXJanY8EqWF01aK
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) p. 3495-3497
E6 Kaplan Sadock's Synopsis of Psychiatry-2022 (pp 1-3768 of 3768) p. 2065-2067
Practise the full IGNOU PB. Bsc. Nsg. Entrance-2025
Attempt every question from this paper in a timed mock, then review the full solution for each one.
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