Muscle weakness, common in Multiple Sclerosis (MS), can occur in any part of the body. The first step in managing weakness effectively is to determine the cause.

One of the main factors in weakness is the deconditioning of muscles, or loss of muscle tone. Deconditioning occurs with a lack of muscle use. With MS, a person’s overall activity level is reduced due to fatigue, pain, imbalance, or other symptoms. Lack of activity will cause weakness in the muscles affected by MS, as well as those that are not affected by the disease. For this type of weakness, progressive resistive exercise with weights can be very effective. A physical therapist can recommend a weight-training program that fits with your abilities and limitations.

One other cause of weakness is demyelination, or the resulting damage to the brain and spinal cord nerve fibers that stimulate the muscles. The muscles do not receiving the nerve impulses they require in order to work effectively – often resulting in decreased endurance. Because the source of this type of weakness is impaired nerve conduction, weight training to strengthen the affected muscles is not effective; in fact, it may even increase feelings of weakness and fatigue. The recommended strategy is to maintain the tone of those muscles that are not receiving adequate nerve conduction. This can be done with using the muscles regularly while working to strengthen the surrounding muscles that are receiving adequate conduction. A physical therapist can work with you to identify the sources of your weakness and recommend appropriate strategies to manage them.

Weakness in the legs, ankles and feet can interfere with walking. Management strategies to address walking problems include exercise, assistive devices, and medication. Weakness in the upper body and arms can interfere with activities of daily living and self-care. Occupational therapists can recommend appropriate exercises for your arms and hands, as well as tools and devices to assist with activities in the home and at work.  ­

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Ampyra®, Dalfampridine, 4-aminopyridine, 4 AP


This medication may improve the conduction of nerve messages through demyelinating plaques in people with multiple sclerosis (MS). It does not prevent multiple sclerosis relapses or progression nor does it repair damage from prior MS lesions. The FDA-approved version, Ampyra®, has an official indication to improve walking in patients with MS. Dalfampridine produced an increase in walking speed in clinical trials. Dalfampridine may also be used for other purposes (off label use) as its effects are not only on motor nerves. Dalfampridine may also be used by some neurologists in a compounded version known as 4-aminopyridine, or 4 AP. This form of the medication may be prepared with different size or dose capsules and used when the FDA approved version is either not covered by insurance or not available in the dose/form your neurologist desires. This version of the medication is felt to have a higher risk for seizures than Ampyra as the compounded capsules may not release the chemical as precisely as the FDA-approved version.

Risks of Ampyra®, Dalfampridine, 4-aminopyridine, 4 AP

You should not use Ampyra®, Dalfampridine, 4-aminopyridine, or 4 AP if you are allergic to any form of it, if you have moderate to severe kidney disease, if you have ever had a seizure (convulsion), or if you are also taking another version of it. Before you take Ampyra®, Dalfampridine, 4-aminopyridine, or 4 AP, tell your doctor if you have kidney disease.

This medication increases your risk of seizures. This risk of seizures is felt to be less with the controlled release FDA version of the drug (Ampyra®) at its usual 10 mg twice per day dose than with the compounded version of the drug. When taking the Ampyra® form do not take more than 2 tablets in a 24-hour period. Do not use a tablet that has been broken or crushed. A broken tablet can release too much of the drug at one time. Stop taking Ampyra® and call your doctor at once if you have a seizure, unusual twitching or jerking, increased nerve pain or other new MS symptoms. If you are unsure if symptoms are related to the medication it is best to stop it. There are no withdrawal symptoms from suddenly stopping this medicine, although weakness may return to its prior level.

FDA pregnancy category C. It is not known whether Dalfampridine, 4-aminopyridine, 4 AP will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medication. It is not known whether dalfampridine passes into breast milk or if it could harm a nursing baby. You should not breast-feed while you are using this medication. Do not give this medication to anyone under 18 years old without the advice of a doctor.

How to take Ampyra®, Dalfampridine, 4-aminopyridine, 4 AP

Take the medication exactly as prescribed by your doctor. Taking too high a dose of Dalfampridine, 4-aminopyridine, 4 AP may increase your risk of seizure. The package’s insert and nurse support program for Ampyra® emphasize that the medication should be taken once every 12 hours. Our doctors often have the medication taken less than 12 hours apart due to the frequent occurrence of insomnia with late day dosing. Follow your doctor's instructions. Do not take more than 2 tablets in a 24-hour period. Ampyra® may be taken with or without food. Do not crush, chew, or break an extended-release tablet. Swallow it whole. Do not dissolve the tablet in liquid. Breaking or dissolving the pill may cause too much of the drug to be released at one time. Do not use an Ampyra® tablet that has been accidentally crushed or broken. This can increase your risk of having a seizure.

To maintain a lower risk for seizures, your kidney function may need to be checked with a blood test periodically. If you develop kidney dysfunction while on this medicine please notify our office so that we may evaluate the continued safety of Dalfampridine, 4-aminopyridine, 4 AP use

Store Ampyra® at room temperature away from moisture and heat.

Throw away any leftover medicine after the expiration date on the label has passed.

If you miss a dose, take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra Ampyra® to make up the missed dose.

If you overdose, seek emergency medical attention or call the Poison Help line at 1-800-222-1222. Ampyra® overdose can cause confusion, problems with thinking or memory, tremors, sweating, or seizures.

Side Effects

Allergic reaction: Get emergency medical help if you have any of these signs of an allergic reaction to Ampyra®: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop taking Ampyra®, Dalfampridine, 4-aminopyridine, or 4 AP and call your doctor at once if you have a serious side effect such as:

  • Seizures (convulsions)
  • New difficulty with emptying bladder or urine control
  • Increased problems with balance
  • Increased uncomfortable nerve feeling such as burning pain or tingling
  • Other worsening of MS symptoms

Less serious Ampyra®, Dalfampridine, 4-aminopyridine, or 4 AP side effects may include:

  • Headache, dizziness
  • Sleep problems (insomnia)
  • Nausea, constipation, upset stomach
  • Weakness
  • Stuffy nose, sinus pain, sore throat
  • Back pain

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