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AMPYRA (dalfampridine) is a potassium channel blocker, available in a 10 mg tablet strength. Each tablet contains 10 mg dalfampridine, formulated as an extended release tablet for twice-daily oral administration. Dalfampridine is also known by its chemical name, 4-aminopyridine.

Clinical pharmacology

Mechanism of action
The mechanism by which dalfampridine exerts its therapeutic effect has not been fully elucidated. Dalfampridine is a broad spectrum potassium channel blocker. In animal studies, dalfampridine has been shown to increase conduction of action potentials in demyelinated axons through inhibition of potassium channels.

AMPYRA does not prolong the QTc interval and does not have a clinically important effect on QRS duration.

Absorption and Distribution:
Orally administered dalfampridine is rapidly and completely absorbed from the gastrointestinal tract. Absolute bioavailability of extended release AMPYRA tablets has not been assessed, but relative bioavailability is 96% when compared to an aqueous oral solution. The extended release tablet delays absorption of dalfampridine relative to the solution formulation, giving a slower rise to a lower peak concentration (Cmax), with no effect on the extent of absorption (AUC). Single AMPYRA tablet 10 mg doses administered to healthy volunteers in a fasted state gave peak concentrations ranging from 17.3 ng/mL to 21.6 ng/mL occurring 3 to 4 hours post-administration (Tmax). In comparison, Cmax with the same 10 mg dose of dalfampridine in an oral solution was 42.7 ng/mL and occurred approximately 1.3 hours after dosing. Exposure increased proportionally with dose.

Dalfampridine is largely unbound to plasma proteins (97-99%). The apparent volume of distribution is 2.6 L/kg.

There is no apparent difference in pharmacokinetic parameter values following administration of AMPYRA tablets to either healthy volunteers or patients with MS.

When dalfampridine is taken with food, there is a slight increase in Cmax (12-17%) and a slight decrease in AUC (4-7%). These changes in exposure are not clinically significant, and therefore the drug may be taken with or without food [see Dosage and Administration].

Metabolism and Elimination:
Dalfampridine and metabolites elimination is nearly complete after 24 hours, with 95.9% of the dose recovered in urine and 0.5% recovered in feces. Most of the excreted radioactivity in urine was parent drug (90.3%). Two metabolites were identified: 3-hydroxy-4-aminopyridine (4.3%) and 3-hydroxy-4-aminopyridine sulfate (2.6%). These metabolites have been shown to have no pharmacologic activity on potassium channels.

The elimination half-life of dalfampridine following administration of the extended release tablet formulation of AMPYRA is 5.2 to 6.5 hours. The plasma half-life of the sulfate conjugate is approximately 7.6 hours and the half-life of 3-hydroxy-4-aminopyridine could not be calculated because concentrations for most subjects were close to or below the limit of quantitation.

In vitro studies with human liver microsomes indicate that CYP2E1 was the major enzyme responsible for the 3-hydroxylation of dalfampridine. The identity of the CYP enzymes suspected of playing a minor role in the 3-hydroxylation of dalfampridine could not be established unequivocally

Indications and usage 

AMPYRA™ (dalfampridine) is a potassium channel blocker indicated to improve walking in patients with multiple sclerosis (MS). This was demonstrated by an increase in walking speed


-History of seizure
-Moderate or severe renal impairment


Seizures: AMPYRA can cause seizures; the risk of seizures increases with increasing AMPYRA doses; AMPYRA is contraindicated in patients with a prior history of seizure; discontinue AMPYRA use if seizure occurs.

Renally impaired patients: AMPYRA is contraindicated in patients with moderate or severe renal impairment (CrCl≤50 mL/min); the risk of seizures in patients with mild renal impairment (CrCl 51-80 mL/min) is unknown, but AMPYRA plasma levels in these patients may approach those seen at a dose of 15 mg twice daily, a dose that may be associated with an increased risk of seizures; estimated CrCl should be known before initiating treatment with AMPYRA.

AMPYRA should not be taken with other forms of 4-aminopyridine (4-AP, fampridine), since the active ingredient is the same.
Urinary tract infections were reported more frequently as adverse reactions in patients receiving AMPYRA 10 mg twice daily compared to placebo.

Pregnancy: Based on animal data, may cause fetal harm.

Nursing Mothers: Discontinue drug or nursing taking into consideration importance of drug to mother.
Pediatric use: Safety and effectiveness of AMPYRA in patients younger than 18 years of age have not been established

Renal Impairment: Clearance of dalfampridine is decreased in patients with renal impairment; AMPYRA is contraindicated in patients with moderate or severe renal impairment (CrCl≤50 mL/min); AMPYRA plasma levels in patients with mild renal impairment (CrCl 51-80 mL/min) may approach those seen at a dose of 15 mg twice daily, a dose which may be associated with an increased risk of seizures.

Geriatric use: Because elderly patients are more likely to have decreased renal function, it is particularly important to know the estimated CrCl in these patients before initiating AMPYRA treatment

Adverse reactions

 The most common adverse events (incidence ≥2% and at a rate greater than the placebo rate) for AMPYRA in MS patients were urinary tract infection, insomnia, dizziness, headache, nausea, asthenia, back pain, balance disorder, multiple sclerosis relapse, paresthesia, nasopharyngitis, constipation, dyspepsia, and pharyngolaryngeal pain.

Dosage and administration 

Maximum recommended dose: 10 mg twice daily (approximately 12 hours apart) with or without food.
Patients should not take double or extra doses if a dose is missed. No additional benefit was demonstrated at doses greater than 10 mg twice daily and adverse events, including seizures, were more frequent at higher doses.
Tablets should only be taken whole; do not divide, crush, chew, or dissolve.

Renal impairment: AMPYRA is contraindicated in patients with moderate or severe renal impairment; the risk of seizures in patients with mild renal impairment is unknown, but AMPYRA plasma levels in these patients may approach those seen at a dose of 15 mg twice daily, a dose that may be associated with an increased risk of seizures.

How supplied

MPYRA (dalfampridine) extended release tablets, 10 mg are a film-coated, white to off-white, biconvex, oval shaped, non-scored tablets with flat edge. The tablets are identified by a debossed code "A10" on one side and are available in bottles of 60.

NDC 10144-427-60 bottles of 60 tablets

Store at 25°C (77°F). Excursions permitted 15-30ºC (59-86ºF).


Package Insert data.

Distributed by: Acorda Therapeutics, Inc.
Hawthorne, NY 10532

Issued 01/2010

AMPYRA™ is a trademark of Acorda Therapeutics, Inc.
Manufactured for Acorda under license from Elan Pharma International Ltd. (EPIL), Ireland, utilizing EPIL's MatriX Drug Absorption System (MXDAS™ technology).
MXDAS™ is a trademark of Elan Pharma International Ltd. (EPIL).
U.S. Patent Nos.: US 5,540,938 and US 5,370,879
©2010, Acorda Therapeutics, Inc. All rights reserved.


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AMPYRA® (dalfampridine)