Pharmacology · patient case with 2 questions
Patient with bipolar disorder and impaired renal function
Patient: Adult with bipolar affective disorder
Chief complaint: Attends for dental assessment.
Background: Bipolar disorder with depression, treated with lithium. Recent lithium overdose.
Vital signs / labs: Renal function reduced to 40% of normal.
Current findings: Multiple medications in use.
Question 1
Which consideration will most affect this patient's care?
Show answer and explanation
Correct answer: A. Altered drug excretion
- A. CORRECT. The kidney is the principal route of elimination for many drugs, and lithium is excreted almost entirely unchanged renally. With function at 40%, drug clearance is substantially impaired, so doses must be reduced and intervals extended. Nephrotoxic drugs, above all NSAIDs, must be avoided — NSAIDs reduce renal lithium clearance and can precipitate toxicity.
- B. Lithium causes xerostomia, which does raise caries risk, but this is secondary to the excretion problem.
- C. The psychiatric condition matters for communication and consent, but the renal impairment is what governs every prescribing decision.
- D. Healing is not the dominant concern here.
Note: Critical interaction: NSAIDs reduce renal lithium clearance and can precipitate lithium toxicity. Choose paracetamol for analgesia in these patients.
Question 2
Which analgesic is most appropriate for this patient?
Show answer and explanation
Correct answer: B. Paracetamol (acetaminophen)
- A. Naproxen carries the same problems.
- B. CORRECT. Paracetamol avoids both the nephrotoxicity and the lithium interaction that make NSAIDs hazardous here. Dose adjustment for renal impairment may still be appropriate.
- C. Diclofenac likewise, with additional cardiovascular concerns.
- D. Ibuprofen is an NSAID: nephrotoxic and raises lithium levels.