<prompt> Half-life of lithium?8 hours16 hours24 hours36 hours  <response>: Ans. c 24 hours. Ref. KD Tripathi, 4th ed., 331, 659LITHIUM Lithium is a small monovalent cation. Lithium carbonate is well absorbed orally. It is neither protein bound nor metabolized. The kidney handles lithium in much the same way as sodium. Most of the filtered lithium is reabsorbed in the PCT. When Na is reabsorbed so is lithium. It has narrow therapeutic window. Average half-life is 20-24 hours. Renal clearance of lithium is l5th of creatinine clearance. On repeated medication steady state plasma concentration is achieved in 5-7 days. This is higher in older patients in those with renal insufficiency. It is used in the treatment of- Acute mania,- - Headache Vascular - SIADH. --Mnemonic: A HSBC- Bipolar disorder mainstay of Rx of acute maniaprophylaxis,- Cancer chemotherapy induced leucopenia neutropenia- Consensus Guidelines for Drug Treatment of Acute Mania and Bipolar Depression: ConditionPreferred Agents1Euphoric maniaLithium2Mixeddysphoric maniaValproic acid3Mania with psychosisValproic acid with olanzapine, conventional antipsychotic, or risperidone4HypomaniaLithium, lamotrigine, or valproic acid alone5Severe depression with psychosisVenlafaxine, bupropion, or paroxetine plus lithium plus olanzapine, or risperidone; consider ECT6Severe depression without psychosisBupropion, paroxetine, sertraline, venlafaxine, or citalopram plus lithium7Miid to moderate depressionLithium or lamotrigine alone; add bupropion if needed 