Fampyra
Potassium Channel Blocker for Improving Walking in Multiple Sclerosis
Quick Facts About Fampyra
Key Takeaways About Fampyra
- Unique MS walking treatment: Fampyra is the only medicine specifically approved to improve walking ability in adults with multiple sclerosis
- Not effective for everyone: Approximately 35–43% of MS patients respond to fampridine; your doctor will assess walking improvement after 2–4 weeks and stop treatment if no benefit is seen
- Strict dosing schedule: Take one 10 mg tablet every 12 hours on an empty stomach; never take more than two tablets per day as higher doses increase seizure risk
- Seizure risk: Fampyra is contraindicated in patients with a history of seizures and in those with moderate or severe kidney impairment, as the drug accumulates and may trigger seizures
- Do not crush or split: The prolonged-release tablet must be swallowed whole to ensure safe, gradual drug release and avoid dangerously high peak blood levels
What Is Fampyra and What Is It Used For?
Fampyra contains the active substance fampridine, a potassium channel blocker that improves walking ability in adults with multiple sclerosis (MS). It is the only approved medicine that specifically targets walking disability caused by MS-related nerve damage.
Fampyra is indicated for the improvement of walking in adult patients (aged 18 years and older) with multiple sclerosis who have walking disability. Multiple sclerosis is a chronic autoimmune disease of the central nervous system in which the immune system attacks the protective myelin sheath that surrounds nerve fibres in the brain and spinal cord. This demyelination disrupts the normal conduction of electrical signals along the nerves, leading to a wide range of neurological symptoms including muscle weakness, muscle stiffness (spasticity), and difficulty walking.
Walking impairment is one of the most common and disabling symptoms of MS, affecting up to 85% of patients during the course of the disease. Difficulty walking significantly impacts quality of life, independence, and the ability to perform everyday activities. Before the approval of fampridine, there was no specific pharmacological treatment targeting walking disability in MS.
How Fampyra Works
Fampridine belongs to a group of medicines called potassium channel blockers. In healthy nerve fibres, the myelin sheath insulates the axon and allows electrical signals (action potentials) to travel rapidly from one node of Ranvier to the next in a process called saltatory conduction. When the myelin sheath is damaged by MS, potassium ions leak out through exposed potassium channels on the demyelinated portions of the nerve fibre. This leakage short-circuits the nerve signal, causing it to slow down, weaken, or fail entirely.
Fampridine works by blocking these voltage-gated potassium channels on the surface of demyelinated axons. By preventing potassium from leaking out, fampridine helps restore more normal action potential propagation along the damaged nerve fibres. This enhanced signal conduction improves the communication between the brain and the leg muscles, which can result in measurably faster and more stable walking.
It is important to understand that fampridine is a symptomatic treatment – it does not modify the underlying disease process of MS, it does not repair damaged myelin, and it does not prevent future relapses or progression. Fampyra is intended to be used alongside disease-modifying therapies (DMTs) that target the underlying autoimmune process.
Fampridine was first approved in the United States in 2010 under the brand name Ampyra (marketed as dalfampridine), and later approved in Europe in 2011 as Fampyra. It has a unique status as the only medicine specifically approved to improve walking in MS. Clinical trials demonstrated that approximately 35–43% of patients experienced a clinically meaningful improvement in walking speed, as measured by the Timed 25-Foot Walk (T25FW) test.
Clinical Evidence
The approval of Fampyra was based on two pivotal phase III randomised, double-blind, placebo-controlled clinical trials (MS-F203 and MS-F204) involving over 540 patients with MS. In these trials, patients treated with fampridine 10 mg twice daily showed a statistically significant improvement in walking speed compared to placebo. The responder rate (patients who showed a consistent improvement in the T25FW test) was approximately 35–43% in the fampridine group compared to 8–9% in the placebo group.
Among responders, the mean improvement in walking speed ranged from approximately 25% to 35%, which is considered a clinically meaningful improvement that translates to real-world functional benefits such as the ability to walk longer distances, cross the street more safely, and maintain greater independence. The European Medicines Agency (EMA) has noted that the beneficial effect is generally evident within the first 2 to 4 weeks of treatment, which is why the initial trial period is recommended.
What Should You Know Before Taking Fampyra?
Before starting Fampyra, your doctor must assess your kidney function and seizure history. Fampyra is strictly contraindicated in patients with a history of seizures, moderate or severe kidney impairment, or concurrent use of other fampridine-containing medicines or cimetidine.
Contraindications
You must not take Fampyra if any of the following apply to you:
- Allergy to fampridine or any of the other ingredients in the medicine – symptoms of allergy may include swelling of the face, mouth, lips, throat, or tongue, skin redness, itching, or difficulty breathing
- History of seizures (epilepsy or convulsions) – fampridine lowers the seizure threshold and can trigger seizures, particularly at higher blood concentrations
- Moderate or severe kidney impairment – because fampridine is primarily excreted by the kidneys (approximately 90% unchanged), reduced kidney function leads to drug accumulation and significantly increased risk of seizures and other adverse effects
- Concurrent use of cimetidine – cimetidine inhibits renal tubular secretion of fampridine, leading to increased drug levels
- Concurrent use of another medicine containing fampridine (4-aminopyridine) – taking additional fampridine from any source increases the risk of serious adverse effects including seizures
Seizures are the most serious dose-dependent adverse effect of fampridine. The risk of seizures increases with higher blood levels of the drug. This is why the dose must never exceed 10 mg twice daily, tablets must never be crushed or split (as this destroys the prolonged-release mechanism), and the medicine is contraindicated in patients with kidney impairment. If you experience a seizure, stop taking Fampyra immediately and contact your doctor.
Warnings and Precautions
Talk to your doctor or pharmacist before taking Fampyra if any of the following apply to you:
- Heart rhythm awareness (palpitations) – fampridine may affect cardiac conduction in some patients, and your doctor may want to monitor you more closely
- Susceptibility to infections – urinary tract infections are a very common side effect of fampridine; your doctor should be aware if you are prone to infections
- Risk factors for seizures or use of medications that lower the seizure threshold – even though frank epilepsy is a contraindication, any factor that increases seizure risk should be discussed with your doctor
- Mild kidney impairment – while not an absolute contraindication, mild kidney impairment may result in higher drug levels; your doctor may monitor your kidney function before and during treatment
- Previous allergic reactions to any medicine – allergic reactions including anaphylaxis and angioedema have been reported with fampridine, and patients with a history of allergic reactions should be monitored
Fampyra may cause dizziness or unsteadiness, which can increase the risk of falls. You should use walking aids (such as a cane or walker) as needed, particularly at the start of treatment. Report any increase in falls or balance difficulties to your doctor.
Elderly Patients
Before starting treatment and during treatment, your doctor may check that your kidneys are functioning properly. This is particularly important in elderly patients, as kidney function naturally declines with age, and even mild reductions in kidney function can lead to higher fampridine blood levels and an increased risk of adverse effects. Your doctor may order blood tests to measure creatinine clearance and adjust the decision to treat accordingly.
Children and Adolescents
Fampyra should not be given to children or adolescents under 18 years of age. The safety and efficacy of fampridine has not been established in this age group, and MS with significant walking disability is uncommon in paediatric populations.
Pregnancy and Breastfeeding
If you are pregnant or breastfeeding, think you may be pregnant, or are planning to have a baby, ask your doctor for advice before taking this medicine. Fampyra is not recommended during pregnancy unless clearly necessary. Animal studies have not indicated direct harmful effects on the developing foetus, but there are no adequate data from the use of fampridine in pregnant women. Your doctor will carefully weigh the benefits of treatment against the potential risk to your baby.
You should not breastfeed while taking Fampyra. It is not known whether fampridine passes into human breast milk, but given its low molecular weight and high bioavailability, excretion into breast milk is likely. The risk to the breastfed infant cannot be excluded, and your doctor may advise you to stop breastfeeding or stop taking the medicine.
Driving and Operating Machinery
Fampyra can cause dizziness, vertigo, and balance disturbances, which may affect your ability to drive or use machines safely. You should not drive or operate machinery until you know how Fampyra affects you. If you experience dizziness or unsteadiness, wait until these symptoms have fully resolved before driving or using machines.
How Does Fampyra Interact with Other Drugs?
Fampyra has significant interactions with medicines that affect kidney excretion. Cimetidine is specifically contraindicated. Other drugs that affect renal clearance, such as carvedilol, propranolol, and metformin, require careful monitoring when used together with fampridine.
Fampridine is minimally metabolised by the liver and is primarily eliminated unchanged through the kidneys via glomerular filtration and active tubular secretion. This means that drug interactions with fampridine are principally related to renal excretion rather than hepatic enzyme pathways. Drugs that inhibit the organic cation transporter 2 (OCT2) in the kidneys can reduce fampridine clearance and increase its blood levels, thereby raising the risk of dose-dependent adverse effects, particularly seizures.
Major Interactions
| Drug | Category | Effect | Recommendation |
|---|---|---|---|
| Cimetidine | H2 receptor antagonist | Inhibits renal tubular secretion of fampridine via OCT2, significantly increasing blood levels | Contraindicated – do not use together |
| Other fampridine / 4-aminopyridine products | Potassium channel blocker | Additive effect increases total fampridine exposure, raising seizure risk | Contraindicated – never combine |
Moderate Interactions
| Drug | Category | Effect | Recommendation |
|---|---|---|---|
| Carvedilol | Beta-blocker | May reduce renal clearance of fampridine via OCT2 inhibition | Use with caution; monitor for adverse effects |
| Propranolol | Beta-blocker | May reduce renal clearance of fampridine via OCT2 inhibition | Use with caution; monitor for adverse effects |
| Metformin | Antidiabetic (biguanide) | Shares OCT2 renal transport pathway; may compete for excretion | Use with caution; monitor kidney function |
| Medicines that lower seizure threshold | Various (tricyclic antidepressants, tramadol, bupropion, etc.) | Additive reduction in seizure threshold when combined with fampridine | Assess individual risk; use under close medical supervision |
Use with MS Disease-Modifying Therapies
Fampyra has been used concomitantly with common MS disease-modifying therapies without clinically significant pharmacokinetic interactions. Fampridine may be taken alongside the following MS treatments:
- Interferon beta (Avonex, Rebif, Betaferon, Plegridy) – no known interaction
- Glatiramer acetate (Copaxone) – no known interaction
- Natalizumab (Tysabri) – no known interaction
- Fingolimod (Gilenya) – no known interaction
- Dimethyl fumarate (Tecfidera) – no known interaction
- Ocrelizumab (Ocrevus) – no known interaction
- Teriflunomide (Aubagio) – no known interaction
However, always inform your doctor about all medicines you are taking, including over-the-counter products, herbal remedies, and dietary supplements. Some over-the-counter cold and flu products may contain ingredients that affect kidney function or seizure threshold.
What Is the Correct Dosage of Fampyra?
The recommended dose of Fampyra is one 10 mg prolonged-release tablet twice daily – one in the morning and one in the evening, approximately 12 hours apart. The tablets must be taken on an empty stomach and swallowed whole. Do not exceed two tablets per day.
Always take this medicine exactly as your doctor has told you. Fampyra is only available on prescription and should be started under the supervision of a doctor with experience in treating MS. Your doctor will typically prescribe an initial course of 2 to 4 weeks. After this trial period, your walking ability will be reassessed – if no improvement is observed, the treatment should be discontinued.
Adults
Standard Adult Dosage
10 mg (one tablet) twice daily – one tablet in the morning and one tablet in the evening, approximately 12 hours apart. This is the only approved dose. Do not take more than two tablets per day.
| Patient Group | Dose | Frequency | Notes |
|---|---|---|---|
| Adults (18+ years) | 10 mg | Twice daily (every 12 hours) | Take on empty stomach; swallow whole |
| Elderly | 10 mg | Twice daily (every 12 hours) | Kidney function must be assessed before and during treatment |
| Mild kidney impairment | 10 mg | Twice daily (every 12 hours) | Use with caution; regular kidney function monitoring |
| Moderate/severe kidney impairment | N/A | N/A | Contraindicated – do not use |
| Children (<18 years) | N/A | N/A | Not recommended – safety not established |
How to Take Fampyra
- Take each tablet by mouth with a drink of water
- Take on an empty stomach – food increases the rate of absorption and raises peak blood levels, which increases the risk of seizures
- Swallow the tablet whole – do not divide, crush, dissolve, suck, or chew the tablet, as this destroys the prolonged-release mechanism and may cause dangerously high peak blood levels
- Maintain a consistent 12-hour interval between doses
- If your tablets come in a bottle containing a desiccant (silica gel), leave the desiccant in the bottle – do not swallow it
Missed Dose
If you forget to take a dose, do not take a double dose to make up for it. You must always allow at least 12 hours between each tablet. If you miss a dose, simply skip it and take your next dose at the regular scheduled time. Taking doses too close together increases the risk of dose-dependent adverse effects, including seizures.
Overdose
If you have taken more Fampyra than you should, contact your doctor or go to the nearest emergency department immediately. Take the medicine packaging with you so that the medical team knows exactly what you have taken.
Symptoms of overdose may include:
- Excessive sweating
- Tremor (minor shaking or trembling)
- Dizziness and confusion
- Memory loss
- Seizures (convulsions)
The risk of seizures is dose-dependent and increases sharply with higher blood levels of fampridine. There is no specific antidote for fampridine overdose. Treatment is supportive, and in severe cases, haemodialysis may be considered to remove the drug from the blood.
Treatment Monitoring and Discontinuation
Your doctor will conduct an initial assessment of your walking ability before starting treatment and then reassess after 2 to 4 weeks. The Timed 25-Foot Walk (T25FW) test is the standard clinical measure used. If you do not demonstrate a meaningful improvement during this initial trial period, your doctor will discontinue the treatment. It is important to note that not all MS patients respond to fampridine – approximately 55–65% of patients do not experience a significant walking benefit.
For patients who do respond, treatment is typically continued for as long as the benefit persists. Your doctor may periodically reassess your walking ability to confirm that the benefit is being maintained. If walking ability declines significantly despite continued treatment, reassessment and possible discontinuation should be considered.
What Are the Side Effects of Fampyra?
Like all medicines, Fampyra can cause side effects, although not everybody gets them. The most common side effect is urinary tract infection. Seizures are the most serious potential side effect and require immediate medical attention. Stop taking Fampyra and seek emergency help if you experience a seizure or signs of a severe allergic reaction.
The side effects listed below are based on data from clinical trials and post-marketing surveillance. Most side effects are mild to moderate in severity and may resolve as your body adjusts to the medicine. However, some side effects require immediate medical attention.
Seizures: If you have a seizure, stop taking Fampyra immediately and tell your doctor. Severe allergic reaction (anaphylaxis): Swelling of the face, mouth, lips, throat, or tongue; skin redness or itching; chest tightness and breathing difficulty. Call emergency services immediately.
Very Common Side Effects
May affect more than 1 in 10 people
- Urinary tract infection
Common Side Effects
May affect up to 1 in 10 people
- Feeling unsteady (balance problems)
- Dizziness
- Vertigo (spinning sensation)
- Headache
- Feeling weak and tired (asthenia)
- Difficulty sleeping (insomnia)
- Anxiety
- Tremor (minor shaking)
- Tingling and numbness in the skin (paraesthesia)
- Sore throat
- Common cold (nasopharyngitis)
- Influenza
- Viral infection
- Shortness of breath (dyspnoea)
- Nausea
- Vomiting
- Constipation
- Stomach upset (dyspepsia)
- Back pain
- Heart palpitations
Uncommon Side Effects
May affect up to 1 in 100 people
- Seizures (convulsions)
- Allergic reaction (hypersensitivity)
- Severe allergic reaction (anaphylactic reaction)
- Swelling of the face, lips, mouth, or tongue (angioedema)
- New onset or worsening of facial nerve pain (trigeminal neuralgia)
- Rapid heartbeat (tachycardia)
- Dizziness or loss of consciousness due to low blood pressure
- Skin rash or itchy rash (urticaria / hives)
- Chest discomfort
Managing Side Effects
Many of the common side effects of Fampyra, such as dizziness, headache, and nausea, tend to be mild and may decrease over time as your body adjusts to the medicine. Here are some practical strategies for managing common side effects:
- Dizziness and balance problems: Use walking aids as needed, especially when starting treatment. Avoid sudden position changes (rising from sitting or lying down). Report persistent dizziness to your doctor
- Urinary tract infections: Stay well hydrated, practice good hygiene, and contact your doctor promptly if you experience symptoms such as burning during urination, frequency, or cloudy urine
- Insomnia: Taking the evening dose at least 3–4 hours before bedtime may help. Maintain a regular sleep schedule and discuss persistent sleep problems with your doctor
- Gastrointestinal symptoms (nausea, constipation): These are usually mild and transient. Ensure adequate fluid intake and dietary fibre. Contact your doctor if symptoms are persistent or severe
Reporting Side Effects
If you experience any side effects, talk to your doctor, pharmacist, or nurse. This includes any possible side effects not listed here. You can also report side effects directly to your national medicines regulatory authority. By reporting side effects, you help provide more information on the safety of this medicine and contribute to ongoing monitoring of its benefit-risk profile.
How Should You Store Fampyra?
Store Fampyra below 25°C in the original packaging to protect from light and moisture. Keep out of the reach and sight of children. If your tablets come in bottles, only open one bottle at a time and use within 7 days of first opening.
Proper storage of medicines is essential to ensure they remain effective and safe throughout their shelf life. Fampyra should be stored in accordance with the following guidelines:
- Temperature: Store at no more than 25°C (77°F). Do not refrigerate or freeze
- Light: Keep in the original packaging to protect from light, as fampridine is light-sensitive
- Moisture: Keep in the original packaging to protect from moisture, as fampridine is moisture-sensitive
- Bottles: If your tablets come in bottles, only open one bottle at a time. Once opened, use the tablets within 7 days. The bottle contains a silica gel desiccant – leave this in the bottle but do not swallow it
- Expiry date: Do not use this medicine after the expiry date stated on the packaging after “EXP”. The expiry date refers to the last day of that month
- Children: Keep this medicine out of the sight and reach of children at all times
Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help to protect the environment and prevent accidental ingestion by others.
What Does Fampyra Contain?
Each Fampyra prolonged-release tablet contains 10 mg of fampridine as the active substance, along with inactive ingredients that form the tablet core and film coating.
Active Ingredient
Each prolonged-release tablet contains 10 mg fampridine (also known as 4-aminopyridine). Fampridine is a small molecule (molecular weight: 94.12 g/mol) that acts as a broad-spectrum potassium channel blocker. Its chemical formula is C5H6N2.
Inactive Ingredients
The inactive ingredients (excipients) serve important functions in the tablet formulation:
- Tablet core: Hypromellose (provides the prolonged-release matrix), microcrystalline cellulose (filler/binder), colloidal anhydrous silica (glidant), magnesium stearate (lubricant)
- Film coating: Hypromellose (film-forming polymer), titanium dioxide E171 (white colouring agent), polyethylene glycol 400 (plasticiser for the film coat)
Appearance and Packaging
Fampyra is an off-white to yellowish-white, film-coated, oval, biconvex prolonged-release tablet measuring 13 × 8 mm, with “A10” debossed on one side. It is available in two packaging types:
- Bottles: HDPE (high-density polyethylene) bottles, each containing 14 tablets and a silica gel desiccant. Pack sizes: 28 tablets (2 bottles) or 56 tablets (4 bottles)
- Blisters: Blister packs of 14 tablets. Pack sizes: 28 tablets (2 blisters) or 56 tablets (4 blisters)
Not all pack sizes may be marketed in your country.
Frequently Asked Questions About Fampyra
Fampyra (fampridine) is used to improve walking ability in adult patients (aged 18 years and over) with multiple sclerosis (MS) who have walking disability. It is the only medicine specifically approved to improve walking in MS. Fampyra works by blocking potassium channels on damaged nerve fibres, allowing nerve signals to pass more normally, which can improve muscle control and walking speed. It is not a cure for MS and does not prevent disease progression.
Your doctor will prescribe an initial trial of 2 to 4 weeks. If you experience a measurable improvement in walking ability during this period (typically assessed with a timed 25-foot walk test), treatment will be continued. If no improvement is seen within the first 2 to 4 weeks, your doctor will stop the treatment. Clinical trials showed that approximately 35–43% of patients experienced a meaningful improvement, so the medicine does not work for all MS patients.
Yes, seizures are a known dose-dependent side effect of fampridine. This is why the dose must not exceed one 10 mg tablet twice daily, with at least 12 hours between doses. Patients with a history of seizures must not take Fampyra. If you experience a seizure while taking Fampyra, stop the medication immediately and contact your doctor. The risk of seizures is increased at higher blood levels, which is why patients with kidney impairment are excluded and the tablets must not be crushed.
Taking Fampyra with food increases the rate of absorption and raises peak blood levels of fampridine. Higher peak levels are associated with an increased risk of seizures and other dose-dependent adverse effects. Taking the medicine on an empty stomach helps ensure that the prolonged-release mechanism works correctly, providing a smoother, more gradual absorption of the active ingredient over the 12-hour dosing interval.
Yes, Fampyra can generally be taken alongside other MS disease-modifying therapies such as interferon beta, glatiramer acetate, natalizumab, fingolimod, dimethyl fumarate, or ocrelizumab. Fampyra is a symptomatic treatment that specifically targets walking ability, not a disease-modifying therapy. However, you must not take Fampyra with any other product containing fampridine or 4-aminopyridine, as this increases the risk of seizures and other serious side effects.
Fampyra is contraindicated in patients with moderate or severe kidney impairment (creatinine clearance below 80 mL/min). Because fampridine is primarily excreted unchanged by the kidneys (approximately 90%), reduced kidney function leads to significantly higher drug levels in the blood, which increases the risk of seizures. Patients with mild kidney impairment may use Fampyra with caution, and their doctor should monitor kidney function regularly throughout treatment.
References
- European Medicines Agency (EMA). Fampyra – Summary of Product Characteristics. Last updated 2025. Available at: ema.europa.eu/en/medicines/human/EPAR/fampyra
- Goodman AD, Brown TR, Krupp LB, et al. Sustained-release oral fampridine in multiple sclerosis: a randomised, double-blind, controlled trial. Lancet. 2009;373(9665):732-738. doi:10.1016/S0140-6736(09)60442-6
- Goodman AD, Brown TR, Edwards KR, et al. A phase 3 trial of extended release oral dalfampridine in multiple sclerosis. Ann Neurol. 2010;68(4):494-502. doi:10.1002/ana.22240
- National Institute for Health and Care Excellence (NICE). Fampridine for treating multiple sclerosis. Technology Appraisal Guidance TA564. Published January 2019.
- Ruck T, Bittner S, Simon OJ, et al. Long-term effects of dalfampridine in patients with multiple sclerosis. J Neurol Sci. 2014;337(1-2):18-24. doi:10.1016/j.jns.2013.11.007
- American Academy of Neurology (AAN). Practice guideline recommendations summary: Disease-modifying therapies for adults with multiple sclerosis. Neurology. 2018;90(17):777-788.
- World Health Organization (WHO). Model List of Essential Medicines. 23rd List, 2023.
- Thompson AJ, Baranzini SE, Geurts J, Hemmer B, Ciccarelli O. Multiple sclerosis. Lancet. 2018;391(10130):1622-1636. doi:10.1016/S0140-6736(18)30481-1
- Mehta LR, Treadway N, Engstrom JW, et al. Fampridine (4-aminopyridine): A review of its pharmacology, efficacy, and tolerability. Expert Rev Neurother. 2019;19(5):389-398.
- EMA Assessment Report. Fampyra (fampridine). Procedure No. EMEA/H/C/002097. European Medicines Agency, 2011.
Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, a group of licensed specialist physicians with expertise in neurology, clinical pharmacology, and evidence-based medicine.
Content developed by physicians specialising in neurology and neurorehabilitation, with clinical experience in managing patients with multiple sclerosis.
Independently reviewed by the iMedic Medical Review Board according to EMA, NICE, and AAN guidelines. All medical claims verified against peer-reviewed literature.
Evidence Level 1A – based on systematic reviews and randomised controlled trials. Following the GRADE evidence framework for evaluating quality of evidence.
No pharmaceutical company funding or commercial sponsorship. All content is editorially independent and free from conflicts of interest.