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Note: lithium
The use and side effects of this difficult and little-understood treatment
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Why read this article?
This article covers how lithium is used in primary care. It includes common side effects, monitoring requirements, interactions and lifestyle advice.
Why is lithium treatment difficult?
Lithium has a narrow therapeutic range. Its target levels are 0.4-1.0mmol/l, with the lower end required in older patients and for maintenance therapy. Toxicity is seen above 1.5mmol/l, and plasma levels over 2.0mmol/l can be fatal. Medicines adherence is low, and the drug can take a year to have a prophylactic effect.
What are the side effects?
Common effects experienced when the drug is used within its therapeutic range include thirst, increased urination and weight gain. Less common side effects include: blurred vision, slight muscle weakness, occasional diarrhoea, fine hand tremor, feeling 'a bit ill'. These side effects can indicate that the dose is too high.
Missed doses
If a dose is missed by less than three hours, it should be taken as normal. If missed by more than three hours, the dose should be omitted.
Rosemary Blackie MRPharmS
Lithium is most commonly used in bipolar disorder, but also in depression, premenstrual tension and unlicensed in cluster headache prophylaxis.1 It was the first effective mood stabiliser, with its antimanic properties first discovered in 1949.2 Despite over 50 years of use, the mechanism of action is still not fully understood.3
As lithium resembles sodium in excitable tissues, it penetrates them via fast voltage-sensitive channels responsible for action potential generation. It is not pumped out to the same degree as sodium and therefore accumulates inside these cells to a greater extent, resulting in partial intracellular potassium loss and partial cell depolarisation.4
Lithium acts selectively in the brain and kidney.4 Acutely, lithium appears to increase brain noradrenaline and serotonin turnover, but inhibit its release on cell depolarisation by noradrenaline-sensitive adenylyl cyclase inhibition, which may produce its antidepressant and antimanic effects.5 It also affects various second-messenger system enzymes, the most well-documented being inositol phosphates.
Its long-term mechanism of action may be due to its alteration of protein kinase C-mediated signalling, changing gene expression and protein production implicated in long-term neuroplastic events.5
Treatment
Lithium is used for the acute and prophylactic treatment of bipolar disorder....