Metabolism and Excretion: Extensively metabolized by N-acetyltransferase 2 (NAT2) to an inactive metabolite. Primarily eliminated in urine (as either unchanged drug or metabolite).
PO (Adults and Children ≥6 yr and ≥45 kg): 15–30 mg/day in 3–5 divided doses; may ↑ by 5 mg/day every 3–4 days based on response and tolerability (not to exceed 20 mg/dose or 100 mg/day). NAT2 poor metabolizers: 15 mg/day in 3–5 divided doses; may ↑ by 5 mg/day every 3–4 days based on response and tolerability (not to exceed 20 mg/dose or 100 mg/day).
PO (Children ≥6 yr and <45 kg): 5–15 mg/day in 3–4 divided doses; may ↑ by 2.5 mg/day every 3–5 days (not to exceed 10 mg/dose or 50 mg/day). NAT2 poor metabolizers: 5 mg/day in 3–5 divided doses; may ↑ by 2.5 mg/day every 3–4 days based on response and tolerability (not to exceed 10 mg/dose or 50 mg/day).
Renal Impairment PO (Adults and Children ≥6 yr and ≥45 kg): CCr 15–90 mL/min: 15 mg/day in 3–5 divided doses; may ↑ by 5 mg/day every 3–4 days based on response and tolerability (not to exceed 20 mg/dose or 100 mg/day).
Renal Impairment (Children ≥6 yr and <45 kg): CCr 15–90 mL/min: 5 mg/day in 3–5 divided doses; may ↑ by 2.5 mg/day every 3–4 days based on response and tolerability (not to exceed 10 mg/dose or 50 mg/day).
Hepatic Impairment (Adults and Children ≥6 yr and ≥45 kg): Mild, moderate, or severe hepatic impairment: 15 mg/day in 3–5 divided doses; may ↑ by 5 mg/day every 3–4 days based on response and tolerability (not to exceed 20 mg/dose or 100 mg/day).
Hepatic Impairment (Children ≥6 yr and <45 kg): Mild, moderate, or severe hepatic impairment: 5 mg/day in 3–5 divided doses; may ↑ by 2.5 mg/day every 3–4 days based on response and tolerability (not to exceed 10 mg/dose or 50 mg/day).
PO Administer without regard to food. Scored tablets may be divided in two. Store tablets in refrigerator; protect from light and moisture. Stable for up to 3 mo.
When patients require a dose in <5 mg increments, have difficulty swallowing tablets, or require feeding tubes, a 1 mg/mL suspension can be prepared by placing the required number of tablets in a 50–100 mL container, adding 10 mL of sterile water for each tablet, waiting for 5 min, and shaking well for 30 sec. Crushing the tablets prior to making the suspension is not necessary. After preparation of the suspension, an oral syringe can be used to draw up and administer the correct dose by mouth or by feeding tube. Refrigerate suspension between doses and shake well before drawing up each dose. Suspension can be stored in refrigerator for up to 24 hr. Discard any unused portion of the suspension after 24 hr.
Instruct patient to take medication as directed and follow dose escalation schedule. Advise patient to omit missed doses. Do not double doses; may increase risk of seizures. Do not change dose or stop medication without consulting health care professional.
Advise patient to notify health care professionals if seizures or signs and symptoms of hypersensitivity reaction (shortness of breath, trouble breathing, swelling of throat or tongue, hives) occur.
Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding. Inform patient of pregnancy exposure registry that monitors pregnancy outcomes in women exposed to Firdapse during pregnancy. Clinicians are encouraged to enroll pregnant patients, or pregnant women may register themselves in the pregnancy registry (855-212-5856) or https://firdapsepregancystudy.com/.