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Medhi B, Prakash O, Jose VM, Pradhan B, Chakrabarty S, Pandhi P
Correspondence: Dr Bikash Medhi, email@example.com
Introduction Lithium still remains an important choice in the therapy of manic-depressive psychosis (MDP), and though there are reports of seasonal variation in lithium levels from a few countries, such studies have not been conducted in India. Variability in the lithium level can lead to lack of efficacy or toxicity, making seasonal variation clinically relevant.
Methods A retrospective case sheet audit was performed for 101 MDP patients for recording plasma lithium level, oral lithium dose, age and gender for one year. The overall average oral lithium dose and level were recorded; the monthly average to which it most closely matched was noted as the control month, and values of other months were compared with this control month by Friedman's test followed by Dunn's test.
Results The mean age of patients was 38.22 (standard deviation 12.07) years, and 72 out of 101 patients were male. The mean lithium dose in November (938.61 +/- 243.40 mg/day), which was the closest to the overall mean dose (938.24 +/- 241.78 mg/day) was taken as the control month, which when compared with other monthly values, did not show any significant difference. The June (0.54 +/- 0.23 meq/L), July (0.55 +/- 0.24 meq/L) and August (0.55 +/- 0.24 meq/L) mean plasma lithium values were significantly high when compared to the October value (0.45 +/- 0.22 meq/L) as control. High-low variability between the plasma lithium values of different months was found to be 25 percent.
Conclusion The present study showed a significant high variability of lithium levels in different months of the year, therefore frequent plasma level monitoring and oral lithium dose adjustment to prevent situations of toxicity and lack of efficacy in MDP.
Keywords: lithium, manic-depressive psychosis, oral lithium, seasonal variation in plasma lithium, therapeutic drug level monitoring
Singapore Med J. 2008; 49(9): 724-7