False statement regarding Lithium is:

There is marked individual variation in the rate of lithium excretion. Thus, with the same daily dose, different individuals attain widely different Antimanic Drugs 435 plasma concentrations. However, in an individual the clearance remains fairly constant. Since the margin of safety is narrow, monitoring of serum lithium concentration is essential for optimal therapy. Serum lithium level is measured 12 hours after the last dose to reflect the steadystate concentration; 0.5-0.8 mEq/L is considered optimum for maintenance therapy in bipolar disorder, while 0.8-1.1 mEq/L is required for episodes of mania. Toxicity symptoms occur frequently when serum levels exceed 1.5 mEq/L. Ref: KD Tripati 8th ed.