Pharmacology · patient case question
Which consideration will most affect this patient's care?
Patient case: 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.
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.