if amifampridine can improve neuromuscular transmission in muscles previously injected with OnabotulinumtoxinA (BTX-A)

Amifampridine may also be effective in treating the sequelae of botulinum toxin injections and this study will determine if neuromuscular transmission as measured by single fiber electromyography is improved in patients treated with BTX-A following administration of amifampridine

Inclusion Criteria:

• Age: 18-80 years of either gender and of any racial background
• Underwent BTX-A injection of facial muscles including frontalis with a total dose between 100-200 units between 80 and 150 days prior to study
• Have decision-making capacity to provide informed consent to study drug dosing and Single Fiber Electromyography (SFEMG)

Exclusion Criteria:

• History of cardiac arrhythmia
• History of seizures or uncontrolled asthma
• History of renal or hepatic disease
• History of any generalized neuromuscular disease
• History of Bell's Palsy or facial nerve trauma
• History of treatment with or sensitivity to amifampridine, 3,4 diaminopyridine (DAP) or 4-aminopyridine (Ampyra®)
• Currently experiencing sequelae of previous BTX-A treatment
• Current use of pyridostigmine (known to alter neuromuscular transmission)
• Use of any investigational drug or device within 30 days of enrollment