Abstract
Background: There have been significant changes in the nature of psychiatric patient populations and patterns of drug prescribing in mood disorders since serum lithium monitoring was introduced. It seems opportune to review current guidelines for target lithium concentration given the decline in lithium monotherapy and increase in the numbers of older people and those with comorbid physical disease administered lithium.
Method: A review was made of the literature of lithium monitoring and target serum concentration in mood disorders, older people, and comorbid physical illness.
Results: Current guidelines, which generally recommend a target serum concentration of 0.5/0.6 to 1.1/1.2 mmol/L, have a number of limitations. A target lithium level of > 0.8 mmol/L is inappropriate given poor tolerability, and adequate efficacy when combination lithium-antipsychotic therapy is used at this or lower levels. Guidelines have largely failed to match specific clinical indications to serum levels, and to consider comorbid physical illness factors known to be associated with lithium toxicity.
Conclusion: For most patients, a target serum lithium concentration range of 0.5–0.8 mmol/L, varying according to clinical indication, age and concurrent physical status, seems most appropriate in enhancing efficacy and minimizing adverse effects. The lower end of this range (0.5–0.6 mmol/L) is recommended for patients 50 years and over; those with diabetes insipidus, renal impairment or thyroid dysfunction; those administered diuretics, angiotensin converting enzyme (ACE) inhibitors or non-steroidal anti-inflammatory drugs (NSAIDs)/COX-2 inhibitors; and in the prophylaxis of bipolar depression and management of acute unipolar depression. The higher end of this range (0.7–0.8 mmol/L) is recommended in the management of acute mania and prophylaxis of mania.
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Acknowledgement
We would like to thank Philip Mitchell who kindly commented on an earlier draft of this paper.
Declaration of interest:
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.