Firdapse for Post-BOTOX Vocal Weakness

Eligibility Criteria

• 1. Male or female ≥18 years of age.
• 2. Capable of providing informed consent.
• 3. Confirmed physician diagnosis of spasmodic dysphonia.
• 4. Receives onabotulinumtoxinA for treatment of their spasmodic dysphonia.
• 5. Experiences significant breathiness ± 5 days following their injection.
• 6. If sexually active and of childbearing potential, willing to use an acceptable method of contraception (as noted below) from screening visit until 3 months after the last dose of investigational product.
• 1. Hormonal contraception (e.g., oral contraceptive, transdermal contraceptive, contraceptive implant, or injectable hormonal contraceptive) for at least 3 months prior to study drug administration, throughout the study, and for 3 months after the last dose of study drug.
• 2. Double-barrier birth control (e.g., a combination of male condom with either cap, diaphragm, or sponge together with spermicide) starting at the Screening visit, throughout the study, and for at least 4 weeks after the last dose of study drug. NOTE: Use of a male and female condom simultaneously is NOT an acceptable method of double-barrier birth control.
• 3. Intrauterine contraception/device starting at the Screening visit, throughout the study, and for 3 months after the last dose of study drug.
• 4. Total abstinence from sexual intercourse (only acceptable if it is the preferred and usual lifestyle of the subject) for at least 1 complete menstrual cycle prior to the Screening visit, throughout the study, and for 3 months after the last dose of study drug.
• 5. Maintenance of a monogamous relationship with a male partner who has been surgically sterilized by vasectomy.
• 1. History of epilepsy and/or on medication/treatment for seizures (such as but not limited to valproic acid, lamotrigine, topiramate, carbamazepine, and phenytoin); or, on certain medications that may lower seizure threshold, such as:
• 1. anaesthetic drugs (propofol),
• 2. antibiotics (penicillins, cephalosporins, imipenem),
• 3. some antidepressants (clomipramine, bupropion, and maprotiline),
• 4. antipsychotics (clozapine, chlorpromazine),
• 5. bronchodilators (aminophylline, theophylline),
• 6. Immunomodifiers (cyclosporine), and
• 7. Narcotic analgesics (pethidine, fentanyl).
• 2. Any SGOT, SGPT that are more than 3x upper limit of normal; and, creatinine that is greater than 2.1
• 3. Women who are pregnant, expecting to get pregnant, or breastfeeding.
• 4. Any condition that, in the view of the Principal Investigator, places the subject at risk, or subjects with poor treatment compliance.