Potassium Channel Blockers for MS: What to Know - WebMD

If you have multiple sclerosis (MS), it's common for it to cause issues with movement and coordination such as loss of balance, difficulty walking, clumsiness, or muscle weakness. Besides physical therapy and walking aids, such as canes and wheelchairs, your doctor may suggest taking a certain potassium channel blocker medication as part of your treatment plan to improve your ability to walk.

How Do Potassium Channel Blockers Work?

The myelin sheath is a protective covering over nerves. When you have MS, your immune system attacks your central nervous system (brain and spinal cord) and destroys the myelin sheath in many areas. This is called demyelination.

When this happens, your nerves aren't able to send and receive messages from the brain as they should. This may cause your muscles to not work right and lead to coordination issues. Experts believe tiny pores on the surface of nerves called potassium channels play a part in the breakdown of electric signals.

While there's no cure for MS, your doctor may prescribe a drug called dalfampridine (Ampyra), a type of broad-spectrum potassium channel blocker, as part of your treatment plan. It's an FDA-approved medication that you take by mouth. It's designed to block potassium channels and strengthen the electric signals sent from your unmyelinated nerve fibers. Studies have found that dalfampridine can improve your ability to walk as well as increase walking speed if you have MS.

Who Can Take Potassium Channel Blockers for MS?

Research shows that regardless of what type of MS you have, dalfampridine may be suitable for you if you have issues with movement and balance.

Clinical trials have shown about a 25% improvement in walking speed. While you're more likely to see changes, you may still need to use assistive devices like canes or a crutch to maintain balance and avoid falling. But if you use a wheelchair, dalfampridine isn't likely to bring back your ability to get around without one.

Dalfampridine isn't suitable for you if you are:

• 18 or under
• Pregnant
• Breastfeeding
• Older with kidney problems

How Should You Take This Medicine?

If your doctor prescribes dalfampridine, you'll likely take 10-milligram pills by mouth twice a day. This is the maximum recommended dose. You may take it with or without food. This is an extended-release drug, so you'll need to take the two doses 12 hours apart. This is because the chemicals are slowly released into your body once you take it. The drug's effects are likely to set in 2-4 weeks after you start taking it.

Take it exactly as directed. If you happen to miss or skip a dose, don't double or take extra doses up as this may increase your risk for side effects. Just take the next pill as scheduled. It's important to swallow the entire tablet. Don't crush or chew it.

What Are the Possible Complications?

If you're taking dalfampridine, you're at a higher risk for:

Seizures. Higher doses of dalfampridine can put you at risk for a seizure. In drug trials, researchers found that if you took 15-milligram pills twice a day instead of the recommended dose, you are four times more likely to have a seizure. If you do have a seizure, stop taking the pills immediately and get medical help as soon as possible. Most seizures usually start within a few days or weeks of starting the medication. If you have a history of seizures, let your doctor know before you take the pills.

Kidney problems. You will pee out 90% of the drug after you take it. If you have moderate to severe kidney problems, this drug may build up in your body and increase your risk for a seizure. It might not be right for you.

It's common to lose some kidney function when you're 50 or older. If you're taking this drug, your doctor will most likely order yearly blood tests to keep a close eye on your kidneys.

What Side Effects Can Potassium Channel Blockers Cause?

Dalfampridine may cause side effects in about 2% of those who use it. This may include:

• Urinary tract infection (UTI)
• Insomnia
• Dizziness
• Headache
• Nausea
• Muscle weakness
• Back pain
• Balance disorder
• Multiple sclerosis relapse
• A pins and needles feeling
• Colds
• Constipation
• Indigestion
• Sore throat

If you notice any of these side effects, tell your doctor immediately.

Things to Know Before You Take Dalfampridine

If you have MS and you're planning to try this drug, here's what you should know:

• You can take dalfampridine along with other disease-modifying agents for MS
• Don't take dalfampridine if you already take fampridine, another type of potassium channel blocker. The two drugs have the same active ingredient.

Dalfampridine may not be able to fix all the problems you may have with balance and movement. Continue to use assistive devices like canes, crutches, walkers, or wheelchairs. There are many other ways to improve your ability to walk besides taking dalfampridine. Talk to your doctor or physical therapist about exercises that may improve your MS-related movement and balance issues.

If you plan to stop taking the recommended doses, ask your doctor how to best taper off.

If you notice allergic reactions when you're on the drug, tell your doctor immediately. If it's a medical emergency, call 911 or head to the nearest hospital.