Fenfluramine for Adult Dravet Patients

Inclusion Criteria: * 1\. Male and female patients 18 years of age and older. 2. Diagnosis of DS secondary to a genetically confirmed pathogenic variant. 3. Patients recruited from the Adult Epilepsy Genetics Clinic at Toronto Western Hospital. We will also accept referrals from other academic epilepsy centers across Ontario and that are referred to our program, making this a single site study. 4\. At least 4 convulsive seizures per month at the start of the study, despite having been treated with at least two different antiepileptic drugs (given concurrently or sequentially) for at least one year. 5\. At least 4 convulsive seizures per month during the prospective Baseline Phase (4 weeks). 6\. Able to provide written consent signed by study participant's caregiver prior to entering the study or undergoing any study procedures. 7\. Participant's caregivers should be able to record seizures and report adverse events for the full duration of the study. 8\. No evidence of non-compliance with ongoing ASM therapy. 9. Stable dose(s) of the same ASMs for one month prior to screening. 10. If participant has a vagal nerve stimulator or deep brain stimulator, it must have been implanted for at least six months prior to recruitment. Stimulator parameters may not be changed for at least one month prior to screening or thereafter during the study. Magnet use will be allowed but must be documented throughout the study. 11\. Patient's caregivers agree that patient will not to take any cannabinoids or any other investigational compound for 1 month before the study or outside cannabinoids during the study. 12\. Patient's caregivers agree that patient will have blood samples taken and stored for assays. 13\. Is planning to stay in the country for the duration of the trial. 14. Can travel to the study site for the initial in-person visit with the study physicians and to a local lab for blood collection (Lifelabs). 15\. Patient's caregiver has access to telephone, computer, and internet to complete the study questionnaires. 16\. Sexually active women of child-bearing potential (WCBP) and males must be using a medically acceptable method of birth control. Women who are of non child-bearing potential, i.e., post-menopause, must have this condition captured in their medical history. A medically acceptable method of birth control includes barrier methods of contraception (e.g. male condom, female condom, cervical cap, diaphragm, contraceptive sponge), intrauterine devices in place for at least 3 months, surgical sterilization, or adequate barrier methods (e.g., diaphragm and foam). Use of oral contraceptives in combination with another method (e.g., a spermicidal cream) is acceptable. In participants who are not sexually active, abstinence is an acceptable form of birth control. Exclusion Criteria: * 1\. Participation in a study involving administration of an investigational compound within one month of First appointment. 2\. Evidence of clinically significant non-epileptic disease (cardiac, respiratory, gastrointestinal, hepatic, hematologic or renal disease, etc.) that in the opinion of the investigators could affect the patient's safety or trial conduct. 3\. Pulmonary hypertension (systolic pressure\>35 mmHg) 4. Cardiovascular or cerebrovascular disease 5. Current or past history of cardiovascular or cerebrovascular disease, such as cardiac valvulopathy defined as greater than moderate and/or mild aortic regurgitation on echocardiogram 6. Treatment with centrally acting anorectic agents, monoamine oxidase inhibitors or other centrally acting agent with serotonin antagonist or agonist properties. 7\. Current or past history of glaucoma 8. Hypersensitivity to FEN or any of the excipients in the study medication 9. Use of CBD oil 10. Pregnant and/or breastfeeding women are excluded from this study. Sexually active women must have negative pregnancy urine test in first in-person visit.