How to Help Your Patients Find Amifampridine (Firdapse) in Stock: A Provider's Guide

For clinicians treating Lambert-Eaton Myasthenic Syndrome (LEMS), getting patients started on amifampridine (Firdapse) requires more than writing a prescription. The drug is dispensed exclusively through specialty pharmacies, subject to mandatory prior authorization, and supported by a manufacturer patient assistance program that your office must help initiate. This guide walks through the practical steps you can take to minimize the time between diagnosis and first dose.

Step 1: Confirm the Diagnosis Comprehensively Before Prescribing

Every payer will require specific diagnostic evidence before approving amifampridine. By ensuring your clinical workup is complete before prescribing, you prevent delays caused by incomplete documentation:

EMG/NCS: Document post-exercise facilitation and CMAP increment on repetitive nerve stimulation at 50 Hz (>60% increment is the typical threshold)

VGCC antibodies: Send voltage-gated calcium channel antibody panel (positive in ~85% of LEMS cases)

Cancer screening: CT chest and PET scan for small-cell lung cancer, which accounts for ~50–60% of LEMS cases

Seizure history: Confirm the patient has no seizure history (amifampridine is contraindicated)

Step 2: Engage Catalyst Pathways at the Time of Prescribing

Do not wait until after prescribing to contact Catalyst Pathways. Initiate enrollment at the same time you write the prescription. Catalyst Pathways (1-833-422-8259) will:

Verify the patient's insurance coverage and identify the in-network specialty pharmacy

Coordinate prior authorization submission on your behalf

Enroll the patient in the copay assistance program ($0/month for eligible commercially insured patients)

Provide free bridge medication if coverage is pending

Step 3: Route the Prescription to the Correct Specialty Pharmacy

Do not send the prescription to a retail pharmacy — they cannot fill it. Firdapse requires a specialty pharmacy that is in-network with the patient's insurance. Catalyst Pathways will identify the correct pharmacy. Common specialty pharmacy networks that dispense amifampridine include CVS Specialty, Walgreens Specialty, Accredo (Express Scripts), Optum Specialty, and Biologics by McKesson. Send the prescription directly by electronic prescribing or fax.

Step 4: Submit a Strong Prior Authorization Letter

Your PA letter is the most important document in the access process. A well-written letter significantly reduces the chances of denial and saves time. Structure your letter to address each of these points:

Patient diagnosis — ICD-10 code G70.80 (Other myasthenia gravis) or G70.89 (Other specified myoneural disorders) with specific LEMS clinical findings

Electrodiagnostic evidence — cite specific EMG values (CMAP amplitudes at rest and post-exercise, percent increment at 50 Hz)

Antibody results — VGCC antibody titer value and reference lab

Functional impairment — use validated tools (QMG score, Timed 25-Foot Walk, dynamometry) to document severity

Treatment rationale — reference FDA labeling: Firdapse is indicated for LEMS in patients 6 years and older (NDA 208078, updated May 2024 with 100 mg/day maximum)

Lack of alternatives — state that no FDA-approved generic exists and that Ruzurgi's approval was withdrawn in 2022

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Step 5: Request Expedited Review When Clinically Appropriate

Standard PA decisions take up to 15 calendar days. If your patient has significant functional impairment, falls, respiratory concerns, or rapidly worsening symptoms, explicitly request an expedited review in writing. Federal regulations require payers to issue expedited decisions within 72 hours when a standard timeline would seriously jeopardize the patient's health. Include a brief clinical urgency statement in your PA submission.

Step 6: Manage Reauthorization Proactively

Amifampridine PAs typically require annual renewal. Payers will require documentation of positive clinical response — improvement in dynamometry, Timed 25-Foot Walk Test, or Timed Up and Go Test. Build clinical response documentation into your routine LEMS follow-up appointments so that reauthorization submissions are straightforward. Track baseline and follow-up values using validated tools.

Skip the calls, skip the stress.

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How medfinder Can Help Your Patients

When your patients are having trouble identifying which specific specialty pharmacy location can fill their prescription, medfinder for providers can help. medfinder calls pharmacies on the patient's behalf to determine which ones can fill the specific medication, then texts the results. This saves patients hours of frustrating phone calls and helps get their prescription moving quickly.

For more detail on the current access environment, see: Amifampridine Shortage: What Providers and Prescribers Need to Know in 2026.