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Abstract
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OBJECTIVE: Lithium is recognized worldwide as an effective prophylactic agent in mood disorders. Prophylactic efficacy of lithium in mood disorders has been established since the early seventies. Lithium has been and continues to be the mainstay of bipolar disorder (BD) pharmacotherapy for acute mood episodes, switch prevention, and suicide prevention. There are reports of seasonal variation in lithium levels from a few countries. Variability in the lithium level can lead to a lack of efficacy or to toxicity, making seasonal variation clinically relevant. We aimed to compare lithium levels of bipolar patients between summer and winter.
METHODS: Euthymic bipolar patients who were followed in the Raşit Tahsin Mood Clinic of the Baki{dotless}rköy Research and Training Hospital for Psychiatry, Neurology and Neurosurgery were recruited for the study, and lithium levels were measured in the second part of winter and summer (15th of June to 1st of September and 15th of January to 1st of March). A prospective case sheet audit was performed for 32 BD patients for recording plasma lithium level, age and gender for one year. Bipolar patients whose treatment dosage of lithium was changed for any reason during the study follow-up were excluded. Situations of lithium use other than for bipolar disorder were excluded. The presence of concomitant diagnoses of mental retardation or drug dependence constituted exclusion criteria, as did medication non-compliance detected by persistently low lithium plasma levels. The use of antihypertensive drugs, nonsteroidal anti-inflammatory drugs, theophylline, some antibiotics, topiramate, and diuretics that could cause an increase in plasma concentrations of lithium, and of theophylline that could reduce lithium concentrations constituted exclusion criteria. Sodium levels were also monitored due to their propable effect on lithium levels. Lithium levels were compared using the paired sample t-test. Correlation analysis was done for the parameters that could affect lithium levels.
RESULTS: The mean age of the patients was 35.75±9.59 years, the mean age of onset was 21.97±6.17 and the mean duration of disorder was 13.90±9.41 year. 15 out of 32 patients were male. The overall average dose of lithium taken by the patients was 1190.6±249.0 mg/day. The mean lithium plasma level was 0.75±0.12 mEq/L in winter, and the mean lithium plasma level was 0.83±0.12 mEq/L in summer (p=0.003). The overall serum sodium levels were 139.1±2.2 mEq/L in summer and 137.1±2.3 mEq/L in winter (p=0.001). The correlation between lithium and sodium levels was not significant in summer or in winter (respectively p=0.55, r=0.12 and p=0.49, r=0.14).
CONCLUSIONS: The present study showed a significant variability of lithium levels when comparing summer and winter. Therefore, frequent plasma level monitoring and oral lithium dose adjustment to prevent situations of toxicity or lack of efficacy in bipolar disorder are suggested. Lithium levels may show a relative increase in summer due to dehydration. Prospective controlled studies are required to differentiate whether this seasonality is specific to bipolar disorders or not.
Language: en |