Fenfluramine

WHY is this medicine prescribed?

Fenfluramine is used to control seizures in children from 2 years of age and older with Dravet syndrome (a disorder that begins in early childhood and causes seizures and later may lead to developmental delays and changes in eating, balance, and walking) and Lennox-Gastaut syndrome (LGS) (a disorder that causes seizures and developmental delays). Fenfluramine is in a class of medications called anticonvulsants. It is not known exactly how fenfluramine works, but it increases the amount of natural substances in the brain that may reduce seizure activity.

HOW should this medicine be used?

Fenfluramine comes as a solution (liquid) to take by mouth. It is usually taken two times a day with or without food. Take fenfluramine at around the same times every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take fenfluramine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Your doctor will probably start you on a low dose of fenfluramine and gradually increase your dose, not more than once every week.

Use the oral syringe that came with the medication for measuring the solution. Do not use a household spoon to measure your dose. Household teaspoons are not accurate measuring devices, and you may receive too much medication or not enough medication if you measure your dose with a household teaspoon. Rinse the oral syringe with clean tap water and allow it to air dry after each use. Use a dry oral syringe each time that you take the medication.

If you have a nasogastric (NG) or gastric tube, your doctor or pharmacist will explain how to prepare fenfluramine to administer it.

Fenfluramine helps to control seizures, but does not cure them. Continue to take fenfluramine even if you feel well. Do not stop taking fenfluramine without talking to your doctor. If you suddenly stop taking fenfluramine, you may experience withdrawal symptoms such as new or worsening seizures. Your doctor will probably decrease your dose gradually.

Are there OTHER USES for this medicine?

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What SPECIAL PRECAUTIONS should I follow?

Before taking fenfluramine,

• tell your doctor and pharmacist if you are allergic to fenfluramine, any other medications, or any of the ingredients in fenfluramine oral solution. Ask your pharmacist or check the Medication Guide for a list of the ingredients.
• Some medications should not be taken with fenfluramine. Make sure you have discussed any medications you are currently taking or plan to take before starting fenfluramine with your doctor and pharmacist. Before starting, stopping, or changing any medications while taking fenfluramine, please get the advice of your doctor or pharmacist. Some medications may need to have their dose adjusted or require extra monitoring while receiving fenfluramine.
• The following nonprescription or herbal products may interact with fenfluramine: dextromethorphan (in cough medications), St. John's Wort, and tryptophan. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking fenfluramine. Do not start any of these medications while taking fenfluramine without discussing it with your healthcare provider.
• tell your doctor if you have or have ever had have glaucoma (increased pressure in the eye that may cause vision loss) or high blood pressure. Also, tell your doctor if you have or have ever had depression, mood problems, suicidal thoughts or behavior or kidney or liver disease.
• tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while taking fenfluramine, call your doctor.
• you should know that fenfluramine may make you drowsy and make it difficult for you to perform activities that require alertness or physical coordination. Do not drive a car or operate machinery until you know how this medication affects you.
• ask your doctor about the safe use of alcoholic beverages and medications containing alcohol (cough and cold products, such as Nyquil, and other liquid products) while you are taking fenfluramine. Alcohol can add to the drowsiness caused by this medication.
• you should know that your mental health may change in unexpected ways and you may become suicidal (thinking about harming or killing yourself or planning or trying to do so) while you are taking fenfluramine. A small number of adults and children 5 years of age and older (about 1 in 500 people) who took anticonvulsants, such as fenfluramine, to treat various conditions during clinical studies became suicidal during their treatment. Some of these people developed suicidal thoughts and behavior as early as one week after they started taking the medication. You and your doctor will decide whether the risks of taking an anticonvulsant medication are greater than the risks of not taking the medication. You, your family, or your caregiver should call your doctor right away if you experience any of the following symptoms: panic attacks; agitation or restlessness; new or worsening irritability, anxiety, or depression; acting on dangerous impulses; difficulty falling or staying asleep; aggressive, angry, or violent behavior; mania (frenzied, abnormally excited mood); thinking about harming or killing yourself, or planning or trying to do so; or any other unusual changes in behavior or mood. Be sure that your family or caregiver knows which symptoms may be serious so they can call the doctor if you are unable to seek treatment on your own.

What SPECIAL DIETARY instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do IF I FORGET to take a dose?

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What SIDE EFFECTS can this medicine cause?

Fenfluramine may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• diarrhea
• constipation
• vomiting
• unsteadiness or problems with walking
• drooling or excessive saliva
• difficulty falling asleep or staying asleep
• falls
• fever, cough, or other signs of infection

Some side effects can be serious. If you experience any of these symptoms or those listed in the IMPORTANT WARNING or SPECIAL PRECAUTIONS sections, stop taking fenfluramine and call your doctor immediately or get emergency medical treatment:

• agitation, hallucinations, fever, sweating, confusion, fast heartbeat, chills, muscle stiffness or twitching, loss of coordination, nausea, vomiting, or diarrhea
• blurred vision or vision changes, including seeing halos (blurred outline around objects) or colored dots

Fenfluramine can cause loss of appetite and weight loss. If you notice your child is losing weight, call your doctor. Your doctor will watch your child's growth and weight carefully. Talk to your doctor if you have concerns about your child's growth or weight while he or she is taking this medication.

Fenfluramine may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (https://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

What should I know about STORAGE and DISPOSAL of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store the oral solution at room temperature and away from excess heat and moisture (not in the bathroom). Do not refrigerate or freeze the solution. Discard any unused oral solution that remains 3 months after first opening the bottle or after the "discard after" date on the label, whichever date is sooner.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location — one that is up and away and out of their sight and reach. https://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (https://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

What should I do in case of OVERDOSE?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

Symptoms of overdose may include:

• dilated pupils
• back arching
• fast or irregular heartbeat
• flushing
• restlessness
• anxiety
• tremors
• seizure
• coma (loss of consciousness for a period of time)

What OTHER INFORMATION should I know?

Do not let anyone else take your medication. Fenfluramine is a controlled substance. Prescriptions may be refilled only a limited number of times; ask your pharmacist if you have any questions.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists, Inc. represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists, Inc. makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

AHFS^® Patient Medication Information™. © Copyright, 2024. The American Society of Health-System Pharmacists^®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: March 15, 2023.