Effectiveness of 3,4-Diaminopyridine in Lambert-Eaton Myasthenic Syndrome

Inclusion Criteria

• Age 18 or over
• Ambulatory while taking 3, 4-DAP, i.e. the patient was able to perform the timed up and go (TUG), either with or without an assistive device
• Established diagnosis of LEMS, with documentation provided
• Continuous use of Jacobus 3, 4-DAP for at least 3 months
• Minimum of 3 doses per day with no single dose less than 10 mg of 3,4-DAP
• The patient needed to wait about 15 to 30 minutes to experience an unequivocal improvement in a LEMS-induced dysfunction after they take their first dose of 3,4-DAP in the morning [a patient who remains in bed past this point by choice may still be eligible]
• Stable regimen of all LEMS-related treatments for at least 3 months
• Stable daily regimen of other medications (prescription and over-the-counter) for a minimum of 1 month
• Willing to chance being tapered off of 3,4-DAP
• Fluency in English
• If applicable, agreed to use birth control during heterosexual intercourse until at least 2 weeks after completion of study
• A signed informed consent by the study subject

Exclusion Criteria

• Last monoclonal antibody treatment (e.g. rituximab) was less than 6 months ago (i.e., recent treatment is an exclusion)
• Clinically significant or poorly controlled condition that in the opinion of the study personnel might pose an unacceptable risk to the patient if entered into the study
• Respiratory failure requiring intubation while on 3,4-DAP with no precipitating event or medication
• Use of any investigational drug other than 3,4-DAP within the last 30 days
• Pregnant or lactating
• Current use of other aminopyridines (e.g.4-AP) or guanidine
• Did not display a sufficiently large response to 3,4-DAP during the baseline observation period in the CRU to detect a decline during withdrawal of 3,4-DAP