Study to Investigate the Safety and Efficacy of Lithium in Volunteers With Amyotrophic Lateral Sclerosis (ALS)

Inclusion Criteria: * Familial or sporadic ALS * Participants diagnosed with laboratory supported probable, clinically possible, probable or definite ALS according to the World Federation of Neurology Revised El Escorial criteria * Disease duration from symptom onset no greater than 36 months at the Screening Visit * Age 18 years or older * Capable of providing informed consent and complying with trial procedures * On a stable dose of riluzole 50 milligrams (mg) twice per day(bid) for at least 30 days prior to screening * Vital capacity (VC) equal to or more than 60% predicted normal value for gender, height and age at the Screening Visit * Creatinine \<1.5 milligrams per deciliter (mg/dl) \[133 micromoles per liter (umol/L\] * Participants maintained on thyroid medication must be euthyroid for at least 3 months before the Screening Visit. * Participants with psoriasis must have inactive disease for at least 30 days before the Screening Visit. * Women must not be able to become pregnant (e.g., post menopausal for at least one year, surgically sterile, or practicing adequate birth control methods) for the duration of the study. Women of childbearing potential must have a negative serum pregnancy test at the Screening Visit and be non-lactating. * Geographic accessibility to the study site Exclusion Criteria: * History of known sensitivity or intolerability to lithium or to any other related compound * Prior exposure to lithium within 90 days of the Screening Visit * Exposure to any investigational agent within 30 days of the Screening Visit * Participants who are malnourished, dehydrated or on a sodium-free diet will be excluded due to the potential side effects of lithium carbonate * Use of digoxin or iodide salts \[e.g. calcium iodide, hydrogen iodide (hydriodic acid), iodide, iodinated glycerol (Organidin), iodine, potassium iodide (SSKI), and sodium iodide supplementation beyond table salt\] * Presence of any of the following clinical conditions: Substance abuse within the past year; Unstable cardiac, pulmonary, renal, hepatic, endocrine, hematologic, or active malignancy or infectious disease; autoimmune deficiency syndrome (AIDS) or AIDS-related complex; Clinically active psoriasis within 30 days of the Screening Visit; Unstable psychiatric illness defined as psychosis (hallucinations or delusions) or untreated major depression within 90 days of the Screening Visit; Screening serum creatinine greater than or equal to 1.5 mg/dL (133 umol/L), thyroid stimulating hormone (TSH) \> 20% above the upper limit; Presence of any clinically significant conduction abnormalities on electrocardiogram (ECG); or Lactating or have a positive serum pregnancy test at the Screening Visit.