A patient presents with drowsiness, dizziness, tinnitus and tremor while taking several medications including lithium. Which medication is the most likely cause of these symptoms?

A patient presents with drowsiness, dizziness, tinnitus and tremor while taking several medications including lithium. Which medication is the most likely cause of these symptoms?

• A. Paracetamol
• B. Codeine
• C. Amlodipine
• D. Lithium

Answer: (D)

Lithium toxicity is the most likely explanation. Lithium has a narrow therapeutic window, so even small increases in its level can produce neurotoxic symptoms such as tremor, drowsiness, and dizziness; tinnitus can occur with CNS toxicity at higher levels. When a patient on several medications shows this exact cluster of symptoms, a drug with known neurotoxic potential like lithium fits best. The other drugs listed don’t typically cause this combination. Paracetamol mainly risks liver injury at overdose and doesn’t usually produce tremor and tinnitus. Codeine can cause sedation and dizziness but not the tremor-tinnitus pattern described. Amlodipine can cause dizziness, but tremor and tinnitus are not characteristic adverse effects of calcium channel blockers. In practice, this pattern should prompt checking the serum lithium level and reviewing concurrent medications or conditions that could raise lithium (such as dehydration or interactions), since toxicity is a key risk with polypharmacy.

Lithium toxicity is the most likely explanation. Lithium has a narrow therapeutic window, so even small increases in its level can produce neurotoxic symptoms such as tremor, drowsiness, and dizziness; tinnitus can occur with CNS toxicity at higher levels. When a patient on several medications shows this exact cluster of symptoms, a drug with known neurotoxic potential like lithium fits best.

The other drugs listed don’t typically cause this combination. Paracetamol mainly risks liver injury at overdose and doesn’t usually produce tremor and tinnitus. Codeine can cause sedation and dizziness but not the tremor-tinnitus pattern described. Amlodipine can cause dizziness, but tremor and tinnitus are not characteristic adverse effects of calcium channel blockers.

In practice, this pattern should prompt checking the serum lithium level and reviewing concurrent medications or conditions that could raise lithium (such as dehydration or interactions), since toxicity is a key risk with polypharmacy.