FAQs About Ruzurgi for LEMS

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by Brian Murphy Ph.D. |

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Ruzurgi for LEMS

Ruzurgi (amifampridine) is a medication by Jacobus Pharmaceutical for the treatment of Lambert-Eaton myasthenic syndrome (LEMS).

The U.S. Food and Drug Administration approved Ruzurgi to treat LEMS patients ages 6 to less than 17. Canada approved the treatment for patients ages 6 and older.

How does Ruzurgi work?

Ruzurgi helps to improve the ability of nerve cells to send signals to muscles. In LEMS, a patient’s own immune system produces antibodies that mistakenly attack calcium channels on the ends of nerve cells that connect to muscles. When these antibodies bind to the calcium channels, these channels cannot open as they should. This interferes with the nerve cell’s ability to send messages to the muscles to contract.

Ruzurgi targets and blocks proteins called potassium channels on neurons, giving any functioning calcium channels extra time to stay open and allow more calcium into the nerve cell. This allows them to release more of a chemical messenger, acetylcholine, leading to stronger muscle contractions.

What is the dosage?

Ruzurgi comes in 10 mg scored tablets to allow for easier splitting into 5 mg portions. A physician will determine the dosage for a child patient. The recommended starting dosage is 15 to 30 mg a day for patients weighing 45 kg (around 99 lbs) or more, and 7.5 mg to 15 mg for patients weighing less than 45 kg. For doses less than 5 mg or for patients who are unable to swallow pills, Ruzurgi can be dissolved in water to form a 1 mg/mL oral solution, which can be given by mouth or through a feeding tube.

Daily doses should be divided into two or three treatments with each dose being 30 mg or less for heavier patients to a maximum of 100 mg daily, and not more than 15 mg for lighter patients to a daily maximum of 50 mg. Ruzurgi can be taken with or without food.

Does Ruzurgi work in all patients?

Patients have different rates of metabolizing Ruzurgi so one child may need a higher or lower dosage than another patient. Doctors will monitor a patient’s progress on each dosage and adjust it as necessary to reach a sufficient level to help control the disease, while minimizing side effects.

What is the difference between Ruzurgi and Firdapse?

Ruzurgi and Firdapse share the same active ingredient, amifampridine. In Ruzurgi, the amifampridine molecule is not attached to other chemicals, but it is bound to the phosphate molecule in Firdapse. In the U.S., Ruzurgi is for patients age 6 to less than 17, while Firdapse is for patients age 17 and older.

What are the side effects?

Patients can experience side effects when taking Ruzurgi, the most serious being seizures and severe allergic reaction such as anaphylaxis. This allergic reaction appears as trouble breathing, swelling of the tongue or throat, or hives.

The most common side effects are tingling in parts of the face, mouth, fingers, toes, or other body parts, pain in the stomach, indigestion, dizziness, and nausea.

Are there reasons a LEMS patient should not take Ruzurgi?

Patients should not take Ruzurgi if they have ever had a seizure, or if they are allergic to amifampridine.

Kidney or liver problems could affect the treatment’s starting dose so patients and their caregivers should consult with physicians.

The safety and efficacy of Ruzurgi has not been tested in children younger than 6 or in women who are pregnant or breastfeeding.

How should Ruzurgi be stored?

Ruzugri tablets can be stored at room temperature between 68 F and 77 F (20 C to 25 C) for up to three months. Any oral suspensions of the medication can safely be stored in the refrigerator for up to 24 hours.


Last updated: Dec. 7, 2020


Lambert-Eaton News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.