A Study of Ranolazine in ALS

Inclusion Criteria: * 18 years or older * Diagnosed with clinically definite, possible, probably, or lab-supported probable ALS per revised El Escorial criteria * Breathing assessment called forced vital capacity (FVC) greater than or equal to 50%. * Able to swallow pills at the start of the study and expected to for the length of the study. * If on ALS modifying medications must be on a stable dose at least 30 days. * Experiencing 4 or more cramps per week during a 2-week screening period. Exclusion Criteria: * Disease duration \< 5 years * Tracheostomy invasive ventilation, or noninvasive ventilation of more than 12 hours/day * Pregnant or lactating, adults unable to consent, and prisoners * Taking ranolazine or investigational drug or has received an investigational drug within 30 days (or 5 half-lives for drugs, whichever is longer) prior to screening * Medically uncontrolled comorbidities (heart, liver, kidney disease) * Baseline QTc interval prolongation \>450 ms for men/ \>470 ms for women, history of long QT syndrome, or medications which prolong the QT interval * Participation in an experimental drug trial less than 30 days before screening * Patients have to be on a stable dosage of any medications used to treat muscle cramps for ≥30 days or have been off these medications ≥30 days prior to randomization.