Amifampridine
Amifampridine is a broad-spectrum potassium channel blocker used to treat Lambert-Eaton Myasthenic Syndrome (LEMS), a rare autoimmune disorder that causes progressive muscle weakness. By blocking potassium channels at the neuromuscular junction, the medication helps improve communication between nerves and muscles, thereby enhancing muscle strength and function in affected patients.
Amifampridine is a potassium channel blocker prescribed to treat muscle weakness in adults with Lambert-Eaton Myasthenic Syndrome (LEMS).
Key facts at a glance
- ATC
- N07XX05
- RxNorm
- 2106338
- Generic
- Amifampridine
- Class
- atc-n07
- Brands
- Firdapse
- Availability
- rx
- Lactation
- unknown
- Routes
- oral
- Forms
- tablet
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 400mg daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
8 groupspregnancy
first trimesteravoid if possible
use only if potential benefits justify potential risks to fetus
regular fetal monitoring including ultrasound
Use with caution and monitor for adverse effects.
pregnancy
second trimesteravoid if possible
continue only if benefits outweigh risks
fetal growth monitoring
Use with caution and monitor for adverse effects.
pregnancy
third trimesteravoid if possible
consider discontinuing before delivery if clinically appropriate
fetal monitoring and assessment for neonatal effects
Use with caution and monitor for adverse effects.
lactation
breastfeedingdiscontinue breastfeeding or avoid drug
do not breastfeed during treatment due to potential excretion in milk
monitor infant for adverse effects
Use of this medication in this population requires careful consideration of risks and benefits.
pediatric_age
children adolescentsnot established
safety and effectiveness not established in patients under 18 years
closely monitor for adverse effects
geriatric
elderlyno specific adjustment required
use with caution, start at lower end of dosing range
monitor renal function and for adverse effects
Use with caution and monitor for adverse effects.
renal_impairment
severe renal impairmentavoid in severe impairment (CrCl <15 mL/min)
contraindicated in patients with severe renal impairment
monitor renal function regularly
Use of this medication in this population requires careful consideration of risks and benefits.
hepatic_impairment
severe hepatic impairmentavoid in severe impairment
contraindicated in severe hepatic impairment due to metabolism in liver
monitor liver function tests
Use of this medication in this population requires careful consideration of risks and benefits.
Statistics and clinical data
FDA approval year
FDA approval for Firdapse (amifampridine) for LEMS treatment
Drug class
Voltage-gated potassium channel blocker
Primary indication
Approved therapeutic indication
Mechanism of action
Pharmacological mechanism
Symptomatic treatment of Lambert-Eaton Myasthenic Syndrome (LEMS) in adult patients. LEMS is a rare autoimmune disorder where antibodies attack the connection between nerves and muscles, resulting in progressive proximal muscle weakness, particularly affecting the limbs.
Amifampridine blocks broad-spectrum potassium channels at the presynaptic neuromuscular junction. This inhibition prolongs the nerve action potential and increases calcium influx into nerve terminals, which enhances acetylcholine release and improves neuromuscular transmission.
The exact therapeutic mechanism in LEMS is not fully elucidated. Use is contraindicated in patients with epilepsy and those taking drugs that lower seizure threshold. Common adverse effects include perioral numbness, paresthesia, and gastrointestinal symptoms. Dosing must be individualized and closely monitored.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 26, 2026. · Read our editorial policy