A Comparison of Serum Lithium Levels for Maintenance Therapy of Bipolar Mood Disorder

Numerous studies have been done on using low serum lithium levels for maintenance therapy of bipolar mood disorder over the past 30-40 years. In this study we sought for the most suitable serum lithium level that having longer relapse's interval periods and less side effects as to recommended it as a maintenance serum lithium level. Thus, we studied 90 patients with bipolar mood disorder (according to DSM-III-R) in a randomized, prospective trial, who were under maintenance lithium therapy and then distributed into two equal groups; group one with serum lithium level between 0.50-0.70 meq/lit and group two between 0.71-0.90 meq/lit., respectively. The mean serum lithium level in group one was 0.62 meq/lit and 0.78 meq/lit for group two. Follow up was done consistently and their serum lithium levels was measured by flame photometry. After gathering data, statistical analysis was performed by X2, result of this study shows that the differences between the two groups with respect to relapse rate with 99 percent reliability was significant, so that 13 patients (34 percent) out of 33 patients of group one and 8 patients (21 percent) out of 38 patients of group two relapsed, and the risk of relapse was 1.6 times higher among patients in group one than among group two. Side effects, including tremor, polyuria, weight gain, nausea, vomiting, metalic taste and insomnia were more frequent in the second group. We conclude that doses resulting in serum lithium levels between 0.71-0.90 meq/lit are more effective in maintenance therapy of bipolar mood disorder than those with 0.5-0.70 meq/lit., although the higher doses are associated with a higher incidence of side effects.