Lithium is mood stabilising drug used most commonly prophylactically in bipolar disorder but also as an adjunct in refractory depression. It has a very narrow therapeutic range (0.4-1.0 mmol/L) and a long plasma half-life being excreted primarily by the kidneys.

Mechanism of action - not fully understood, two theories:

• interferes with inositol triphosphate formation
• interferes with cAMP formation

Adverse effects

• nausea/vomiting, diarrhoea
• fine tremor
• nephrotoxicity: polyuria, secondary to nephrogenic diabetes insipidus
• thyroid enlargement, may lead to hypothyroidism
• ECG: T wave flattening/inversion
• weight gain
• idiopathic intracranial hypertension
• leucocytosis
• hyperparathyroidism and resultant hypercalcaemia

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N+V+D, Ts - Tremor + Thyroid down + T wave down + nephroToxic (renal down)

Ups - Weight, ICH, WCC, Parathyroid → Ca++

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Monitoring of patients on lithium therapy

• inadequate monitoring of patients taking lithium is common - NICE and the National Patient Safety Agency (NPSA) have issued guidance to try and address this. As a result it is often an exam hot topic
• when checking lithium levels, the sample should be taken 12 hours post-dose
• after starting lithium levels should be performed weekly and after each dose change until concentrations are stable