Medically reviewed by Drugs.com. Last updated on Mar 18, 2022.
Commonly used brand name(s)
In the U.S.
Available Dosage Forms:
Therapeutic Class: Central Nervous System Agent
Pharmacologic Class: Potassium Channel Blocker
Uses for amifampridine
Amifampridine is used to treat Lambert-Eaton myasthenic syndrome (LEMS), a rare autoimmune disease, wherein the immune system attacks the connection between the nerve and muscle (neuromuscular junction) and blocks the ability of the nerve cells to send signals to the muscle cells, leading to muscle weakness of the arms or legs.
Amifampridine is available only with your doctor's prescription.
Before using amifampridine
In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For amifampridine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to amifampridine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Appropriate studies have not been performed on the relationship of age to the effects of Firdapse® in children and Ruzurgi® in children younger than 6 years of age. Safety and efficacy have not been established.
No information is available on the relationship of age to the effects of Ruzurgi® in geriatric patients.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of Firdapse® in the elderly. However, elderly patients are more likely to have age-related liver, kidney, or heart problems, which may require caution and an adjustment in the dose for patients receiving amifampridine.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with medicines
Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking amifampridine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using amifampridine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Amdinocillin Pivoxil
- Belladonna Alkaloids
- Conjugated Estrogens
- Esterified Estrogens
- Ethinyl Estradiol
- Mefenamic Acid
- Nalidixic Acid
- Penicillin G
- Penicillin V
- Polyestradiol Phosphate
Interactions with food/tobacco/alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.
Other medical problems
The presence of other medical problems may affect the use of amifampridine. Make sure you tell your doctor if you have any other medical problems, especially:
- Kidney disease or
- Liver disease—Use with caution. The effects may be increased because of the slower removal of the medicine from the body.
- Seizures, history of—Should not be used in patients with this condition.
Proper use of amifampridine
Take amifampridine only as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered.
Amifampridine comes with a Medication Guide and patient information leaflet. Read and follow these instructions carefully. Ask your doctor if you have any questions.
You may take amifampridine with or without food.
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.
If your child cannot swallow the Ruzurgi® 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.
The dose of amifampridine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of amifampridine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For oral dosage form (tablets):
- For Lambert-Eaton myasthenic syndrome:
- Adults—At first, 15 milligrams (mg) to 30 mg given in 3 to 4 divided doses per day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 80 mg total per day.
- Children—Use and dose must be determined by your doctor.
- Children 6 to 16 years of age weighing 45 kilograms (kg) or more—Dose is based on body weight and must be determined by your doctor. At first, 15 milligrams (mg) to 30 mg given 2 to 3 divided doses per day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 100 mg total per day.
- Children 6 to 16 years of age weighing less than 45 kg—Dose is based on body weight and must be determined by your doctor. At first, 7.5 mg to 15 mg given 2 to 3 divided doses per day. Your doctor may adjust your dose as needed. However, the dose is usually not more than 50 mg total per day.
- Children less than 6 years of age—Use and dose must be determined by your doctor.
- For Lambert-Eaton myasthenic syndrome:
If you miss a dose of amifampridine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
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.
Precautions while using amifampridine
It is very important that your doctor check your or your child's progress at regular visits to make sure amifampridine is working properly.
Amifampridine may increase your risk for seizures and should not be given to patients who have had seizures.
Amifampridine may cause serious allergic reactions, including anaphylaxis, which can be life-threatening and requires immediate medical attention. Tell your doctor right away if you have a rash, itching, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth after using amifampridine.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.
Amifampridine side effects
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- Arm or leg pain
- bladder pain
- bloating or swelling of the face, arms, hands, lower legs, or feet
- bloody or cloudy urine
- blurred vision
- burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
- chest pain
- cough producing mucus
- difficult, burning, or painful urination
- difficulty breathing or swallowing
- frequent urge to urinate
- general feeling of discomfort or illness
- joint pain
- loss of appetite
- lower back or side pain
- muscle pains, spasms, or weakness
- pounding in the ears
- rapid weight gain
- runny nose
- slow or fast heartbeat
- sore throat
- swollen, painful, or tender lymph glands in the neck, armpit, or groin
- tightness of the chest
- trouble sleeping
- unusual tiredness or weakness
- unusual weight gain or loss
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- Back pain
- decreased vision
- feeling cold
- feeling sad or empty
- lack or loss of strength
- loss of interest or pleasure
- pale skin
- stomach pain
- trouble concentrating
- troubled breathing with exertion
- unusual bleeding or bruising
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Frequently asked questions
- What is the difference between Ruzurgi and Firdapse?
- What is Firdapse (amifampridine) used to treat?
More about amifampridine
- Side effects
- Drug interactions
- Dosage information
- During pregnancy or Breastfeeding
- Reviews (5)
- En español
- Drug class: cholinergic muscle stimulants
- Latest FDA Alerts (1)
Related treatment guides
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.