Amifampridine

Amifampridine is used to treat Lambert-Eaton myasthenic syndrome (LEMS).

Amifampridine is available under the following different brand names: Firdapse and Ruzurgi.

Dosages of Amifampridine:

Dosage Forms and Strengths

Tablet

• 10 mg

Dosage Considerations – Should be Given as Follows:

Lambert-Eaton Myasthenic Syndrome

• Adults
  • 15-30 mg/day orally in divided doses (3-4 times daily) initially; may increase by 5 mg/day every 3-4 days; not to exceed 80 mg/day
  • Maximum single dose: 20 mg

• Children 6 to 17 years and weighing less than 45 kg
  • Ruzurgi only
  • 7.5-15 mg/day, in divided doses (2-3 times/day) initially
  • May increase based on clinical response and tolerability by 2.5- to 5-mg increments, divided into up to 5 doses/day
  • The maximum single dose is 15 mg; not to exceed 50 mg/day

• Children 6 to 17 years and weighing 45 kg or greater
  • Ruzurgi only
  • 15-30 mg orally daily in divided doses (2-3 times/day) initially
  • May increase based on clinical response and tolerability by 5- to 10-mg increments, divided into up to 5 doses/day
  • The maximum single dose is 30 mg; not to exceed 100 mg/day

• Children under 6 years: Safety and efficacy not established

Dosage Modifications

Renal impairment

• Adults: CrCl 15-90 mL/minute: Recommended starting dose is 15 mg/day orally in 3 divided doses; monitor closely; consider dosage modification or discontinuation if needed based on effect and tolerability
• Children under 45 kg: Starting dose; CrCl 15-90 mL/minute: 7.5 mg/day orally in divided doses
• Children 45 kg and greater: Starting dose; CrCl 15-90 mL/minute: 15 mg/day orally in divided doses
• End-stage renal disease (CrCl less than 15 mL/minute): No recommendation can be made

Hepatic impairment

• Not studied
• Extensively metabolized by N-acetyltransferase 2 (NAT2), and hepatic impairment may cause an increase in exposure
• Adults: Recommended starting dose: 15 mg/day orally in 3 divided doses; monitor closely
• Children under 45 kg: Starting dose; CrCl 15-90 mL/minute: 15 mg/day orally in divided doses
• Children 45 kg and greater: Starting dose for any degree of hepatic impairment: 15 mg/day orally in divided doses
• Consider dosage modification or discontinuation if needed based on effect and tolerability

NAT2 poor metabolizers

• Adults: Recommended starting dose: 15 mg/day orally in 3 divided doses; monitor closely
• Consider dosage modification needed based on clinical effect and tolerability
• Starting dose children under 45 kg: 7.5 mg/day orally in divided doses
• Starting dose children 45 kg and greater: 15 mg/day orally in divided doses

Common side effects of amifampridine include:

• Numbness and tingling
• Upper respiratory tract infection
• Abdominal pain
• Nausea
• Diarrhea
• Headache
• Elevated liver enzymes
• Back pain
• High blood pressure (hypertension)
• Muscle spasms
• Dizziness
• Lethargy
• Muscular weakness
• Pain in extremities
• Cataracts
• Constipation
• Bronchitis
• Fall
• Swollen lymph nodes
• Seizures

Side effects of amifampridine (Ruzurgi) include:

• Numbness and tingling
• Abdominal pain
• Indigestion/heartburn
• Dizziness
• Nausea
• Back pain
• Reduced sense of touch
• Muscle spasms

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

• Amifampridine has no listed severe interactions with other drugs.
• Amifampridine has no listed serious interactions with other drugs.
• Amifampridine has moderate interactions with at least 88 different drugs.
• Amifampridine has no listed mild interactions with other drugs.

Warnings

• This medication contains amifampridine. Do not take Firdapse or Ruzurgi if you are allergic to amifampridine or any ingredients contained in this drug.

Contraindications

• History of seizures
• Hypersensitivity to amifampridine phosphate or another aminopyridine

Effects of Drug Abuse

• No information is available.

Short-Term Effects

• See "What Are Side Effects Associated with Using Amifampridine?"

Long-Term Effects

• See "What Are Side Effects Associated with Using Amifampridine?"

Cautions

If hypersensitivity reaction (e.g., anaphylaxis) occurs, discontinue the drug and initiate appropriate therapy

Seizures

• Can cause seizures; consider discontinuation or dose reduction in patients who have a seizure while on treatment
• Many instances of seizure were in patients taking medications or who had comorbid conditions that may have lowered seizure threshold
• Contraindicated in patients with a history of seizures

Drug interactions overview

• Drugs that lower seizure threshold: Coadministration may increase the risk of seizures
• Drugs with cholinergic effects: Coadministration may increase the risk of adverse cholinergic effects

Pregnancy and Lactation

• No data are available on the use of amifampridine in pregnant women. Based on animal studies, amifampridine can cause fetal harm (e.g., stillbirths, reduced fetal weight, delayed sexual development) at doses associated with maternal plasma drug levels lower than therapeutic drug levels. Consult your doctor.
• It is unknown if amifampridine is distributed in human breast milk. In lactating rats, amifampridine was excreted in milk and reached levels similar to those in maternal plasma. Consider the developmental and health benefits of breastfeeding along with the mother's clinical need for the drug, and any potential adverse effects on the breastfed infant from the drug or the underlying maternal condition.