False statement regarding Lithium is

(No individuals variation in the rate of excretion) (416-KDT) (389-BB) (435-KDT 6th)LITHIUM - is well absorbed orally and is neither protein bound nor metabolized*** High peak plasma concentrations are avoided by using sustained-release formulations which deliver the peak plasma lithium concentration in about 5 hour (389-BB).* Only the kidneys eliminate lithium. Like sodium, it is filtered by the Glomerulus and 80% is reabsorbed by the proximal tubule but it is not reabsorbed by the distal tubule (389-BB).* **There is marked individual variation in the rate of lithium excretion. Thus with the same daily dose, different individuals attain widely different plasma concentration. Since the margin of safety is narrow, monitoring serum lithium is essential for optimum therapy** * Lithium is contraindicated during pregnancy, and sick sinus syndrome.