An Open-Label Extension Trial to Assess the Long-Term Safety of ZX008 (Fenfluramine Hydrochloride HCl) Oral Solution in Children and Young Adults With Dravet Syndrome

Key Inclusion Criteria: * Male or non-pregnant, non-lactating female, age 2 to 18 years, inclusive as of the day of the core study Screening Visit. * Satisfactory completion of the core study in the opinion of the investigator and the sponsor. * Subjects who are \>18 to ≤35 years of age at the time of screening and did not participate in one of the core studies may be eligible for participation. * A documented medical history to support a clinical diagnosis of Dravet syndrome, where convulsive seizures are not completely controlled by current antiepileptic drugs. * Parent/caregiver is willing and able to be compliant with diary completion, visit schedule and study drug accountability. * Subject's parent/caregiver has been compliant with diary completion during the core study, in the opinion of the investigator (eg, at least 90% compliant). Key Exclusion Criteria: * Current or past history of cardiovascular or cerebrovascular disease, myocardial infarction or stroke. * Current cardiac valvulopathy or pulmonary hypertension that is clinically significant and warrants discontinuation of study medication. * Current or past history of glaucoma. * Moderate or severe hepatic impairment. * Receiving concomitant therapy with: centrally-acting anorectic agents; monoamineoxidase inhibitors; any centrally-acting compound with clinically appreciable amount of serotonin agonist or antagonist properties, including serotonin reuptake inhibition; atomoxetine, or other centrally-acting nora…