lithium - definition of lithium in the Medical dictionary - by the Free Online Medical Dictionary, Thesaurus and Encyclopedia.a silver-white alkali metal occurring in various compounds such as petalite and spodumene. Its atomic number is 3; its atomic mass is 6.94. Lithium is the lightest known metal and one of the most reactive elements. Traces of lithium ion occur in animal tissue, and it abounds in many alkaline mineral spring waters. Its salts are used in the treatment of manias, but the mechanisms by which these compounds help to stabilize psychologic moods are not understood. Lithium carbonate is a salt commonly used for psychiatric purposes in the United States. It has been effective in the prevention of recurrent attacks of manic-depressive illnesses and has helped correct sleep disorders in manic patients, apparently by suppressing the rapid eye movement phases of sleep. Therapeutic concentrations of lithium have no observable psychotropic effects on normal individuals. In manic patients, lithium salts also produce high-voltage slow waves in the electroencephalograph, often with superimposed beta waves. An important feature of the lithium ion is its relatively small gradient of distribution across biologic membranes. Patients suffering severe manic attacks are hospitalized so that they can receive proper medical maintenance. Treatments start with large doses of antipsychotic drugs, which are followed by the gradual and safe introduction of lithium therapy. Ideally lithium treatment is prescribed only for patients with normal sodium intake and normal heart and kidney function.
