Amifampridine phosphate is used to treat a certain disorder that affects nerves and muscles (Lambert-Eaton syndrome). This disorder causes your body's immune system to attack healthy nerve cells, which results in muscle weakness. It is not known exactly how this medication works, but it can help lessen symptoms of muscle weakness and loss of movement caused by Lambert-Eaton syndrome.

Read the Medication Guide provided by your pharmacist before you start taking amifampridine phosphate and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth with or without food as directed by your doctor, usually 3 to 5 times daily. The dosage is based on your medical condition and response to treatment. Children's dosage is also based on weight. To reduce your risk of side effects, your doctor may direct you to start this medication at a low dose and gradually increase your dose. Follow your doctor's instructions carefully.

If you need a dose that doesn't match taking half and/or whole tablets together, or have trouble swallowing tablets, or receive medication through a feeding tube, you may make a liquid suspension with this medication. Read and follow the manufacturer's directions (Instructions for Use leaflet) to make a suspension with the tablet(s) and sterile water. Ask your doctor or pharmacist about what you need to make the suspension. Place the required number of tablets in a container. Add 10 milliliters (2 teaspoonfuls) sterile water to the container for each tablet. Do not use any other foods or liquids to mix this medication. Wait 5 minutes, then shake the mixture well for 30 seconds. Shake the suspension well before measuring each dose. Carefully measure the dose using a special measuring device/spoon. Do not use a household spoon because you may not get the correct dose. Refrigerate the suspension between doses. Prepare fresh suspensions daily. Throw away any unused suspension after 24 hours.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day.

Tell your doctor if your condition does not get better or if it gets worse.

Tingling around the mouth, tongue, face, fingers, toes, and other body parts may occur. Cold symptoms (such as stuffy/runny nose, cough, sore throat, fever, sneezing), nausea, diarrhea, constipation, headache, stomach/back pain, muscle spasms, or dizziness may also occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

This medication may raise your blood pressure. Check your blood pressure regularly and tell your doctor if the results are high.

Tell your doctor right away if you have any serious side effects, including:

• symptoms of liver damage (such as nausea/vomiting that doesn't stop, loss of appetite, stomach/abdominal pain, yellowing eyes/skin, dark urine)
• vision changes (such as decreased/blurred vision)

Get medical help right away if you have any very serious side effects, including:

• seizure

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking amifampridine phosphate, tell your doctor or pharmacist if you are allergic to it; or to amifampridine; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• kidney problems
• liver problems
• seizure

This drug may make you dizzy. Alcohol or marijuana can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this medication passes into breast milk. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Amifampridine phosphate is very similar to amifampridine. Do not switch brands unless directed by your doctor.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: severe dizziness, fast/irregular heartbeat, fainting.

Do not share this medication with others.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store the tablets at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

If you are using the liquid suspension, store it in the refrigerator. After mixing, discard any unused suspension after 24 hours. (See also How to Use section.)

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.