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Amifampridine (By mouth)

Amifampridine (am-i-FAM-pri-deen)

Treats Lambert-Eaton myasthenic syndrome (LEMS).

Brand Name(s):

Firdapse, Ruzurgi

There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

This medicine is not right for everyone. Do not use it if you had an allergic reaction to amifampridine or similar medicine, or if you have a history of seizures.

How to Use This Medicine:


  • Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.
  • The tablets may be divided in half at the score (line at the center) if you need less than a full tablet to get the right dose.
  • Ruzurgi®: If your child cannot swallow the tablet or needs to take it using a feeding tube, you may prepare a suspension. Mix three tablets with 30 milliliters (mL) of water in a 30-mL container, then shake the mixture well for 30 seconds. You may give the dose using an oral syringe or feeding tube. Shake the medicine well before giving each dose.
  • This medicine should come with a Medication Guide. Ask your pharmacist for a copy if you do not have one.
  • Missed dose: Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.
  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
  • Store Ruzurgi® tablets at room temperature for up to 3 months. Keep Ruzurgi® suspension in the refrigerator for up to 24 hours. Throw away any unused liquid after 24 hours.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Some medicines can affect how amifampridine works. Tell your doctor if you are using pyridostigmine or other aminopyridine medicines (including compounded 3,4-diaminopyridine, amifampridine, or 4-aminopyridine).

Warnings While Using This Medicine:

  • Tell your doctor if you are pregnant or breastfeeding, or if you have kidney disease or liver disease.
  • This medicine may increase your risk of seizures.
  • Your doctor will check your progress and the effects of this medicine at regular visits. Keep all appointments.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Numbness, tingling, or burning pain in your hands, arms, legs, or feet
  • Seizures, muscle spasms, arm or leg pain

If you notice these less serious side effects, talk with your doctor:

  • Back pain
  • Cough, sore throat, runny or stuffy nose, body aches
  • Dizziness, headache
  • Nausea, diarrhea, stomach pain, constipation

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 3/19/2020

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