Nuedexta for the Prevention and Modification of Disease Progression in Episodic Migraine

Inclusion Criteria: * male or female, in otherwise good health, 18 to 65 years of age. * history of frequent episodic migraine for at least 3 months as defined by 6-14 migraine days per month with or without aura according to the ICHD-3beta or a migraine treated with an ergot or triptan which resulted in relief. * onset of migraine before age 50. * stable history of headache at least 3 months prior to screening. * if using daily migraine preventive medications for migraine or for other medical conditions (e.g. propranolol being used for hypertension) and has been on a stable dose and regimen for at least 2 months prior to beginning the baseline period. * female, of childbearing potential, and agrees to maintain true abstinence or use (or have their partner use) one of the listed methods of birth control for the duration of the study: hormonal contraceptive, intrauterine device (IUD), condoms, diaphragm, and/or vasectomy. The use of barrier contraceptive (condom or diaphragm) should always be supplemented with the use of a spermicide. Note: To be considered not of childbearing potential, subject must be 6 weeks post-surgical bilateral oophorectomy, hysterectomy, or bilateral tubal ligation, or postmenopausal for at least one year. Exclusion Criteria: * unable to understand the study requirements, the informed consent, or complete headache records as required per protocol. * pregnant, actively trying to become pregnant, or breast-feeding. * female of childbearing potential not using adequate contraceptive measures. * experienced the following migraine variants: basilar migraine, aura without headache, familial hemiplegic migraine, complicated migraine, ophthalmoplegic migraine and retinal migraine. * history of Medication Overuse Headache (Appendix II) in the 3 months prior to study enrollment or during the baseline phase. * history of acute migraine treatment greater than 14 days per month in 3 months prior to screening. * history of 3 or more failed preventative medications due to lack of efficacy for prophylactic treatment of migraine after an adequate therapeutic trial. * received onabotulinumtoxinA injections within 3 months prior to screening and/or will receive onabotulinumtoxinA injections during the study. * abused, in the opinion of the Investigator, any of the following drugs, currently or within the past 1 year: opioids, alcohol, barbiturates, benzodiazepine, cocaine. * taken, or plans to take: a monoamine oxidase inhibitor (MAOI) including herbal preparations containing St. John's wort (Hypericum perforatum) within 14 days of Visit 1, concomitant medications and/or foods containing dextromethorphan, quinidine, quinine, mefloquine, paxil, dicyclomine, digitalis, thioridazine or pimozide (medications that prolong QT interval) anytime within the 2 weeks prior to screening through 2 weeks post final study treatment. * history of hypersensitivity to medications containing dextromethorphan. * history of hypersensitivity to medications or foods containing quinidine. * at an increased risk of developing serotonin syndrome, in the opinion of the investigator. * history of impaired hepatic or renal function that, in the investigator's opinion, contraindicates participation in this study. * unstable neurological condition or a significantly abnormal neurological examination with focal signs or signs of increased intracranial pressure. * cardiovascular disease (ischemic heart disease, including angina pectoris, myocardial infarction, documented silent ischemia, or with Prinzmetal's angina); has symptoms of ischemic heart disease, ischemic abdominal syndromes, peripheral vascular disease or Raynaud's Syndrome. * ECG results outside normal limits (\> 470 msec), prolonged QT interval, congenital long QT syndrome, torsades de pointes, or complete AV block. * has uncontrolled hypertension (≥ 140/90mmHg in either the systolic or diastolic measurements in 2 out of 3 BP readings at screening). * serious illness, or an unstable medical condition, one that could require hospitalization, or could increase the risk of adverse events, in the opinion of the investigator. * any psychiatric disorder with psychotic features and any other psychiatric disorder not stable or well controlled, that would interfere in their ability to complete study activities. * received any investigational agents within 30 days prior to Visit 1. * plans to participate in another clinical study at any time during this study.