Answers to Frequently Asked Questions

  • What is FIRDAPSE?

    FIRDAPSE® (amifampridine) tablets 10 mg is the first and only FDA-approved, evidence-based medication for adults with Lambert-Eaton myasthenic syndrome.

    FIRDAPSE is the approved brand name for amifampridine phosphate, which is the active ingredient in FIRDAPSE. Amifampridine phosphate quickly becomes amifampridine freebase in the body and may also be referred to as 3,4-diaminopyridine or 3,4-DAP.

  • Can FIRDAPSE be used in people less than 17 years old?

    The FDA-approved indication is for the treatment of Lambert-Eaton myasthenic syndrome in adults aged 17 and older.

  • How does FIRDAPSE work?

    In patients with Lambert-Eaton myasthenic syndrome (LEMS), antibodies block the calcium channels in nerve cells, reducing the amount of acetylcholine (ACh) available in the neuromuscular junction. ACh is the chemical that tells muscles when to contract and move.

    FIRDAPSE works by blocking the potassium channels in nerve cells, which is thought to keep the calcium channels open longer and allow more ACh to be released. Beyond this, the mechanism of action has not been well described.

  • What is in FIRDAPSE?

    The active ingredient in FIRDAPSE is amifampridine phosphate, which is a voltage-gated potassium channel blocker. An active ingredient is responsible for the medicine’s effect. Each FIRDAPSE tablet contains 10 mg of amifampridine (equivalent to 18.98 mg of amifampridine phosphate). Each FIRDAPSE tablet also contains 1.5 mg of phosphorus, which allows FIRDAPSE to be stored at room temperature for extended periods without refrigeration.

    Many medicines also contain “inactive” ingredients, which are considered to be generally recognized as safe (GRAS) by the US Food and Drug Administration (FDA).

    The tablet includes the following inactive ingredients: calcium stearate, colloidal silicon dioxide, and microcrystalline cellulose. Inactive ingredients are often added during a drug’s manufacturing process but do not affect how the active ingredient works. FIRDAPSE is gluten free.

  • Why does FIRDAPSE have phosphate in it?

    The use of amifampridine phosphate allows FIRDAPSE to be stored at room temperature for extended periods without refrigeration. Each tablet of FIRDAPSE contains 1.5 mg of phosphorus, which is an essential nutrient for the human body.

    The recommended daily allowance of phosphorus is 700 mg per day for adults. At the maximum dose (8 tablets per day), a person would get 12 mg per day of phosphorus from FIRDAPSE, which is 1.7% of the recommended daily allowance.

  • Does FIRDAPSE have magnesium in it?

    No, FIRDAPSE does not contain any magnesium or magnesium stearate, which are inactive ingredients found in other medicines.

    The only other approved product that contains amifampridine (approved for an indication distinct and separate from that of FIRDAPSE) has 10 mg of 3,4-DAP freebase but also contains inactive ingredients, including magnesium stearate as well as colloidal silicon dioxide, dibasic calcium phosphate dihydrate, microcrystalline cellulose, and sodium starch glycolate.

  • What is the difference in the ingredients of FIRDAPSE and RUZURGI?

    FIRDAPSE and RUZURGI® (amifampridine) contain the same active ingredient—amifampridine. An active ingredient is responsible for the medicine’s effect. FIRDAPSE contains 18.98 mg of amifampridine phosphate, which is the same 10 mg of amifampridine freebase found in RUZURGI, but it enters the bloodstream quickly and could make it feel different to patients who are used to amifampridine freebase. The amifampridine phosphate salt form of the active ingredient allows for longer stability at room temperature—so it never needs to be refrigerated at any point in its supply chain.

  • How does FIRDAPSE differ from current treatment options for LEMS?

    There have been other treatments used for patients with Lambert-Eaton myasthenic syndrome (LEMS), but they have not been fully studied, reviewed by the FDA, or established in clinical trials as being effective.

    FIRDAPSE is the first and only medication that has been FDA-approved to treat adults with LEMS after more than 70 studies over 9 years to verify that it is safe and effective.

    Two of these studies were Phase 3 clinical trials that confirmed that FIRDAPSE is a safe and effective treatment for anyone aged 17 and older who has been diagnosed with LEMS.

  • Does FIRDAPSE work the same as other 3,4-DAP products?

    Yes. The active ingredient in FIRDAPSE is amifampridine, which is also known as 3,4-diaminopyridine or 3,4-DAP. Any medicine containing amifampridine is thought to block potassium channels in nerve cells, which signals the nerve cells to release more acetylcholine (ACh) into muscles for improved muscle function. Beyond this, the specifics on how 3,4-DAP works have not been well described. FIRDAPSE has been shown to produce the same effect as 3,4-DAP.

  • How much FIRDAPSE should I take on a daily basis?

    You and your doctor will work together to determine the right daily dose of FIRDAPSE for you.

    Based on clinical studies:

    • The recommended starting dose is 15 mg to 30 mg daily taken orally in divided doses (3 to 4 times daily)
    • The maximum single dose to take at once is 20 mg
    • Dosage is not to exceed a maximum of 80 mg daily
    • The starting dosage is 15 mg daily for patients with renal or hepatic impairment and individuals known to be poor metabolizers of N-acetyltransferase 2 (NAT2)
    • Dosage can be increased by 5 mg daily every 3 to 4 days

    In the clinical studies, the average total daily dose was 60 mg, and the range was between 30 mg and 80 mg.

  • How is the best dose for each patient identified or determined?

    Dosing was established from clinical trials in patients with LEMS. According to the package insert, the starting dose is 15 mg to 30 mg per day, but your doctor may tell you to increase your dose every 3 to 4 days if you are not feeling enough benefit. Many patients may find that the best dose for them is less than 60 mg per day, but many can go as high as 80 mg per day. The average daily dose across all patients in clinical studies was 60 mg.

    Ultimately, you and your doctor will work together to determine the optimal daily dose of FIRDAPSE for you.

  • What is titration?

    Medicine can work differently in each person. That’s why you and your doctor will work together to try different doses (or amounts) of FIRDAPSE to find the one that reduces your symptoms the most while avoiding as many side effects as possible. This process is called titration. As part of your enrollment in Catalyst Pathways™, you’ll also receive one-on-one titration support from a Patient Access Liaison (PAL) to help with this process.

    For FIRDAPSE, this means that the starting dose is usually 15 mg to 30 mg per day, but your doctor may tell you to increase your dose every 3 to 4 days if you are not feeling enough benefit. Many patients may find that the best dose for them is less than 60 mg a day, but many can go as high as 80 mg per day. The average daily dose across all patients in clinical studies was 60 mg.

    Talk to your doctor to learn more about why and how you should titrate with FIRDAPSE.

  • How do I take FIRDAPSE?

    Take FIRDAPSE exactly as your doctor has prescribed it. Only you and your doctor can determine the right course of therapy for you.

  • What is the FIRDAPSE pill size?

    FIRDAPSE 10-mg tablets are white to off-white, round, and functionally scored.

  • Can the pill be chewed?

    FIRDAPSE pills cannot be chewed. Talk to your doctor if you are unable or unwilling to swallow the medication as directed.

  • How is FIRDAPSE stored?

    FIRDAPSE should be stored at 68° to 77°F (20° to 25°C). FIRDAPSE was intentionally formulated to improve stability and increase shelf life at room temperature for up to 2 years.

  • What side effects should I expect?

    As with any product containing amifampridine, you may feel tingling, nausea, and diarrhea when you first start taking your medicine and until you find the right dose for you. These should subside over time. Talk to your doctor about any side effects that you may feel while taking your medicine. You and your doctor can work together to try different doses of FIRDAPSE until you find the dose that reduces your symptoms the most with the least amount of tingling, nausea, and diarrhea. See the full Prescribing Information for FIRDAPSE for a complete list of side effects.

  • What should I do if I experience side effects?

    Talk to your doctor immediately about any side effects that you may feel while on your medicine. Your doctor may provide suggestions to manage these effects, which could include adjusting your dose of FIRDAPSE or trying additional therapy to manage side effects. In the case of an emergency, immediately contact 911.

  • Is it normal to have tingling when I start taking FIRDAPSE?

    In clinical studies, 64% of patients who were newly treated with FIRDAPSE experienced tingling around the mouth, hands, or arms. This is common with medicine containing amifampridine. This feeling subsided in most patients during the studies. Your healthcare provider will help you to manage any side effects that you may have and will help you decide on the appropriate next steps (eg, adjusting your dose).

  • What should I do if FIRDAPSE is not working for me?

    The amount of medicine you take in each dose, when you take the dose, and the overall amount each day can affect the level of FIRDAPSE in the blood. And the level of FIRDAPSE in the blood can lead to different levels of effectiveness.

    There are several reasons why different people could have different blood levels at the same dose and therefore experience more or less effectiveness from the medicine:

    • Your genetic metabolism profile can affect levels of amifampridine in the blood in significant and predictable ways, and your doctor can work with you to determine the best dosing to address your situation
    • Whether or not the medicine is taken on an empty stomach may impact the speed and length of time that amifampridine phosphate is absorbed into the bloodstream for some patients

    Talk to your doctor about your treatment goals and carefully review your experience during the titration process. Your doctor may decide to increase your dose or suggest additional medicine to enhance the effect of FIRDAPSE at 80 mg per day.

  • What types of drugs have cholinergic effects? How do they increase the risk of adverse reactions?

    Cholinergic effects may be experienced with any type of medication that influences the action of the chemical neurotransmitter acetylcholine (ACh), which is the primary chemical transmitter for nerve impulses that tells muscles when to contract and move.

    “Cholinergic agonists” is the name given to a group of medicines that mimic the actions of ACh. The use of cholinergic agonists, like Salagen (pilocarpine) or Evoxac (cevimeline), is limited because of their likelihood to cause side effects, including blurred vision, cramps and diarrhea, low blood pressure and decreased heart rate, nausea and vomiting, salivation and sweating, shortness of breath, and increased urinary frequency.

    The concomitant use of FIRDAPSE and drugs with cholinergic effects, such as cholinergic agonists, may increase the cholinergic effects of FIRDAPSE and of those drugs, as well as increase the risk of adverse reactions. Your doctor will help decide which medications may or may not be safe to take with FIRDAPSE.

    You should always make sure that your doctor is aware of ALL medications you are taking when they are considering new medications for you.

  • What is a NAT2 poor metabolizer? How do I know if I’m a NAT2 poor metabolizer?

    All medicines are processed in various ways by the body. N-acetyltransferase 2 (NAT2) is an enzyme in your body that has an important role in processing many drugs, including FIRDAPSE. Due to genetic differences in how this enzyme works, each person’s ability to process these medicines varies. Some people may be “fast metabolizers,” and some people may be “slow (poor) metabolizers.” Regardless of whether you are a fast or slow metabolizer, FIRDAPSE will be individually titrated to account for this effect (see the “What is titration?” question above to learn more about how FIRDAPSE is titrated). Slow metabolizers will generally require a lower dose of FIRDAPSE, whereas fast metabolizers will generally require a higher dose of FIRDAPSE to achieve the same effect (up to 80 mg per day). In other words, a “fast metabolizer” may need to achieve a higher daily dose of FIRDAPSE to see benefits similar to a “slow metabolizer.”

    In clinical trials, the average daily dose of FIRDAPSE was approximately 60 mg per day. These differences in how people process medicine is why, when you are starting FIRDAPSE, it is important to contact your doctor’s office every 3 to 4 days during titration to tell them how you are feeling. This way, a physician can follow each person’s response to the medication and find their most effective dose based on their own NAT2 enzyme status.

    Whether someone is a fast or slow NAT2 metabolizer is a little more complex. Fast and slow metabolizers represent the two extremes of NAT2 enzyme processing; there is a broad range of rates between those extremes. Knowing your specific status would not change how FIRDAPSE is used or titrated because there is such a wide variety of individual NAT2 responses. If you work closely with your doctor to adjust your dose to find the best benefit of FIRDAPSE with the most manageable side effects, you will reach your individualized optimal FIRDAPSE dose regardless of your NAT2 metabolizer status.

    Have your doctor contact a Catalyst Medical Sales Liaison if they have additional questions.

  • Where and how is FIRDAPSE made?

    All of Catalyst’s plants are located in the US or Canada. FIRDAPSE is made based on good manufacturing practices (GMPs).

    GMPs are implemented by the US Food and Drug Administration (FDA) to ensure that medicines made for humans meet quality standards for safety and effectiveness. GMPs lead to consistent quality by requiring that:

    • The medicine matches what is on the label
    • The quality, purity, and potency of the medicine are consistent from batch to batch
    • Buildings, equipment, and processes used to manufacture products are properly designed, monitored, and controlled
  • How long was FIRDAPSE in clinical development? How many clinical and nonclinical studies did Catalyst complete before the approval of FIRDAPSE for treatment in adult patients with LEMS?

    FIRDAPSE was in clinical development from 2009 to 2018, with work done by both Catalyst and BioMarin, our licensing partner. Over the 9-year period before receiving FDA approval at the end of 2018, FIRDAPSE was tested in more than 70 studies to help determine safety and efficacy, including two larger Phase 3 clinical studies in patients with Lambert-Eaton myasthenic syndrome (LEMS).

  • What are the key findings of the clinical research on FIRDAPSE?

    Clinical studies have shown that patients who started and stayed on FIRDAPSE suffered less muscle weakness compared to patients who did not take FIRDAPSE. These results were based on an objective assessment of arm strength, leg strength, face and neck muscle performance, swallowing, speech, grip strength, forced breathing, gaze impairment, and other measures.

    In these clinical studies, patients also reported feeling better while on FIRDAPSE. Patients were asked to rate how they felt FIRDAPSE was affecting their physical well-being on a 7-point scale, known as the Subject Global Impression (SGI) scale.

  • Is FIRDAPSE being studied for other diseases?

    Yes. Catalyst is committed to developing new, safe, and effective treatments that will improve the lives of people with rare and ultra-rare diseases. We are currently researching ways to expand the use of FIRDAPSE for other rare neurological disorders. If you’d like to learn more, contact us at Catalyst Pharmaceuticals, or visit our Research & Pipeline page at CatalystPharma.com.

  • Is FIRDAPSE approved for use elsewhere in the world?

    Yes. It was approved on December 28, 2009 for use in patients with Lambert-Eaton myasthenic syndrome in the European Union and is made available by the company BioMarin.

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What is FIRDAPSE®?

FIRDAPSE is a prescription medicine used to treat adults 17 years of age or older with Lambert-Eaton myasthenic syndrome (LEMS). The safety and efficacy of FIRDAPSE in patients under the age of 17 has not been established.

IMPORTANT SAFETY INFORMATION

What is the most important information I should know about FIRDAPSE?

  • FIRDAPSE can cause seizures.
    • You could have a seizure even if you never had a seizure before.
    • Do not take FIRDAPSE if you have ever had a seizure.

Stop taking FIRDAPSE and call your doctor right away if you have a seizure while taking FIRDAPSE.

Do not take FIRDAPSE if you:

  • have ever had a seizure.
  • are allergic to amifampridine phosphate, or another aminopyridine.

Before you take FIRDAPSE, tell your doctor about all of your medical conditions, including if you:

  • are taking another aminopyridine, such as compounded 3,4-diaminopyridine (3,4-DAP)
  • have had a seizure
  • have kidney problems
  • have liver problems
  • are pregnant or plan to become pregnant. It is not known if FIRDAPSE will harm your unborn baby. You and your doctor will decide if you should take FIRDAPSE while you are pregnant.
  • are breastfeeding or plan to breastfeed. It is not known if FIRDAPSE passes into your breast milk. Talk to your doctor about the best way to feed your baby while taking FIRDAPSE.

Tell your doctor about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

How should I take FIRDAPSE?

  • Take FIRDAPSE exactly as your doctor tells you to take it. Do not change your dose of FIRDAPSE.
  • Do not take more than 2 tablets of FIRDAPSE at one time or more than 8 tablets of FIRDAPSE in a 24-hour period.
  • FIRDAPSE can be taken with or without food.
  • If you miss a dose of FIRDAPSE, skip that dose and take your next dose at your next scheduled dose time. Do not double your dose to make up the missed dose.
  • Do not take FIRDAPSE together with other medicines known to increase the risk of seizures.
  • If you take too much FIRDAPSE, call your doctor or go to the nearest hospital emergency room right away.

What are the possible side effects of FIRDAPSE?

FIRDAPSE may cause serious side effects, including:

  • Seizures. See "What is the most important information I should know about FIRDAPSE?"
  • Serious allergic reactions, such as anaphylaxis. FIRDAPSE can cause serious allergic reactions. Stop taking FIRDAPSE and call your doctor right away or get emergency medical help if you have:
    • shortness of breath or trouble breathing
    • swelling of your throat or tongue
    • ­hives
  • The most common side effects of FIRDAPSE include:
    • tingling around the mouth, tongue, face, fingers, toes, and other body parts
    • upper respiratory infection
    • stomach pain
    • nausea
    • diarrhea
    • headache
    • increased liver enzymes
    • back pain
    • high blood pressure
    • muscle spasms

Tell your doctor if you have any side effect that bothers you or that does not go away.

These are not all the possible side effects of FIRDAPSE.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

How should I store FIRDAPSE?

  • Store FIRDAPSE at 68ºF to 77ºF (20ºC to 25ºC).
  • Safely throw away FIRDAPSE that is out of date or no longer needed.

Keep FIRDAPSE and all medicines out of the reach of children.

If you would like more information, ask your doctor or pharmacist for additional information about FIRDAPSE.

The active ingredient in FIRDAPSE is amifampridine phosphate. Inactive ingredients are calcium stearate, colloidal silicon dioxide, and microcrystalline cellulose.

Please see full Prescribing Information for additional Important Safety Information.

What is FIRDAPSE®?

FIRDAPSE is a prescription medicine used to treat adults 17 years of age or older with Lambert-Eaton myasthenic syndrome (LEMS). The safety and efficacy of FIRDAPSE in patients under the age of 17 has not been established.

IMPORTANT SAFETY INFORMATION

What is the most important information I should know about FIRDAPSE?

  • FIRDAPSE can cause seizures.
    • You could have a seizure even if you never had a seizure before.
    • Do not take FIRDAPSE if you have ever had a seizure.

Stop taking FIRDAPSE and call your doctor right away if you have a seizure while taking FIRDAPSE.

Do not take FIRDAPSE if you:

  • have ever had a seizure.
  • are allergic to amifampridine phosphate, or another aminopyridine.

Before you take FIRDAPSE, tell your doctor about all of your medical conditions, including if you:

  • are taking another aminopyridine, such as compounded 3,4-diaminopyridine (3,4-DAP)
  • have had a seizure
  • have kidney problems
  • have liver problems
  • are pregnant or plan to become pregnant. It is not known if FIRDAPSE will harm your unborn baby. You and your doctor will decide if you should take FIRDAPSE while you are pregnant.
  • are breastfeeding or plan to breastfeed. It is not known if FIRDAPSE passes into your breast milk. Talk to your doctor about the best way to feed your baby while taking FIRDAPSE.

Tell your doctor about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

How should I take FIRDAPSE?

  • Take FIRDAPSE exactly as your doctor tells you to take it. Do not change your dose of FIRDAPSE.
  • Do not take more than 2 tablets of FIRDAPSE at one time or more than 8 tablets of FIRDAPSE in a 24-hour period.
  • FIRDAPSE can be taken with or without food.
  • If you miss a dose of FIRDAPSE, skip that dose and take your next dose at your next scheduled dose time. Do not double your dose to make up the missed dose.
  • Do not take FIRDAPSE together with other medicines known to increase the risk of seizures.
  • If you take too much FIRDAPSE, call your doctor or go to the nearest hospital emergency room right away.

What are the possible side effects of FIRDAPSE?

FIRDAPSE may cause serious side effects, including:

  • Seizures. See "What is the most important information I should know about FIRDAPSE?"
  • Serious allergic reactions, such as anaphylaxis. FIRDAPSE can cause serious allergic reactions. Stop taking FIRDAPSE and call your doctor right away or get emergency medical help if you have:
    • shortness of breath or trouble breathing
    • swelling of your throat or tongue
    • ­hives
  • The most common side effects of FIRDAPSE include:
    • tingling around the mouth, tongue, face, fingers, toes, and other body parts
    • upper respiratory infection
    • stomach pain
    • nausea
    • diarrhea
    • headache
    • increased liver enzymes
    • back pain
    • high blood pressure
    • muscle spasms

Tell your doctor if you have any side effect that bothers you or that does not go away.

These are not all the possible side effects of FIRDAPSE.

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

How should I store FIRDAPSE?

  • Store FIRDAPSE at 68ºF to 77ºF (20ºC to 25ºC).
  • Safely throw away FIRDAPSE that is out of date or no longer needed.

Keep FIRDAPSE and all medicines out of the reach of children.

If you would like more information, ask your doctor or pharmacist for additional information about FIRDAPSE.

The active ingredient in FIRDAPSE is amifampridine phosphate. Inactive ingredients are calcium stearate, colloidal silicon dioxide, and microcrystalline cellulose.

Please see full Prescribing Information for additional Important Safety Information.