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Lithium Tremor — MRCPsych Paper B MCQ

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ModerateMood DisordersLithium TremorMRCPsych Paper B

A 47-year-old man with bipolar disorder remains well on modified-release lithium, which has provided effective relapse prevention. He develops a functionally troublesome fine, bilateral postural hand tremor. A correctly timed 12-hour serum lithium concentration is 0.7 mmol/L, and renal and thyroid function are normal. He has no gastrointestinal symptoms, confusion, ataxia or other features of lithium toxicity. His pulse is 76 beats/min, blood pressure is 128/78 mmHg, and he has no history of asthma or cardiac conduction disease. What is the most appropriate next pharmacological step?

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Correct answer: D — Add low-dose propranolol

The correct answer is D. A fine, symmetrical postural tremor can occur as an adverse effect of lithium despite a therapeutic serum concentration. The absence of coarse tremor, ataxia, confusion or gastrointestinal symptoms makes clinically significant lithium toxicity unlikely. Because lithium remains effective and the tremor is troublesome, low-dose propranolol, cautiously titrated after checking contraindications, is the best option offered. Discontinuing lithium or switching to valproate would unnecessarily sacrifice effective relapse prevention. Deliberately producing a subtherapeutic lithium concentration risks loss of efficacy. Immediate-release lithium may increase peak-related adverse effects rather than improve them. Contributing factors such as caffeine, anxiety and interacting medicines should also be reviewed.

Reference: Morgan JC et al. Medical and Surgical Treatment for Medication-Induced Tremor: Case Report and Systematic Review. Movement Disorders Clinical Practice. 2022. https://pubmed.ncbi.nlm.nih.gov/35844282/