General Information

Ruzurgi (amifampridine) is a potassium channel blocker.

Ruzurgi is specifically indicated for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in patients 6 to less than 17 years of age.

Ruzurgi is supplied as a tablet for oral administration. The recommended dose is as follows:

Patients 6 to less than 17 years of age and weighing 45 kg or more:

• Initial dose is 15 to 30 mg daily, in divided doses. Increase daily in 5 to 10 mg increments, divided in up to 5 doses daily
• Maximum single dose is 30 mg; maximum daily dose is 100 mg

Patients 6 to less than 17 years and weighing less than 45 kg:

• Initial dose is 7.5 to 15 mg daily, in divided doses. Increase daily in 2.5 mg to 5 mg increments, divided in up to 5 doses daily
• Maximum single dose is 15 mg; maximum daily dose is 50 mg.

Mechanism of Action

Ruzurgi (amifampridine) is a potassium channel blocker. The mechanism by which Ruzurgi exerts its therapeutic effects on LEMS patients is not fully understood.

Side Effects

Adverse effects associated with the use of Ruzurgi may include, but are not limited to, the following:

• burning or prickling sensation (paresthesia)
• abdominal pain
• indigestion
• dizziness
• nausea
• Seizures have been observed in patients without a history of seizures.

Clinical Trial Results

The FDA approval of Ruzurgi was based on a randomized, double-blind, placebo-controlled withdrawal study of 32 adult patients in which patients were taking Ruzurgi for at least three months prior to entering the study. The study compared patients continuing on Ruzurgi to patients switched to placebo. The primary measure of efficacy was the categorization of the degree of change (e.g., greater than 30% deterioration) in the Triple Timed Up and Go test (3TUG) upon withdrawal of active medication, when compared with the time-matched average of the 3TUG assessments at baseline. The 3TUG is a measure of the time it takes a person to rise from a chair, walk 3 meters, and return to the chair for 3 consecutive laps without pause. Higher 3TUG scores represent greater impairment. None of the patients randomized to continue on Ruzurgi experienced a greater than 30% deterioration in the final post-dose 3TUG test. In contrast, 72% of the patients in the placebo group did experience a greater than 30% deterioration in the final post-dose 3TUG test.