ModifiedmhnPolicy CP.PHAR.411

Amifampridine (Firdapse) for Lambert-Eaton Myasthenic Syndrome

Defines medical necessity and prior authorization criteria for Firdapse (amifampridine) to treat Lambert-Eaton myasthenic syndrome (LEMS) for commercial, HIM, and Medicaid lines of business; affects prescribers, pharmacies, and health plan reviewers.

Policy Summary

Payermhn

PolicyAmifampridine (Firdapse) for Lambert-Eaton Myasthenic Syndrome

Policy CodePolicy CP.PHAR.411

Change TypeAnnual review — material revisions

Effective DateJan 22, 2022

Next Review Date

Key ActionSubmit prior authorization with documentation that member meets all approval criteria, including baseline clinical muscle strength assessment.

SourceLink

POLICY UPDATE CHANGES

Initial approval duration revised from 6 to 12 months.

Requirement that requests do not exceed health plan-approved quantity limit was added.

Maximum dose modified per updated prescribing information.

Initial approval duration revised from 6 to 12 months.

References reviewed and updated as part of annual review.

≥6Min age (FDA)

100 mg/dayMax dose ≥45 kg

50 mg/dayMax dose <45 kg

12 mo

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10 mg tabProduct format

Coverage Criteria for Amifampridine (Firdapse)

Initial Therapy

Covered when ALL of the following are met for Initial Approval (LEMS):

Initial Approval - LEMS: 1) Diagnosis of Lambert-Eaton myasthenic syndrome (LEMS); 2) Documentation of confirmatory diagnostic test results from one of the following: (a) Repetitive Nerve Stimulation (RNS) showing reproducible post-exercise increase in compound muscle action potential (CMAP) amplitude of at least 60% compared with pre-exercise baseline or a similar increment on high-frequency RNS without exercise; OR (b) if member is unable to complete RNS testing, positive anti-P/Q-type voltage-gated calcium channel (VGCC) antibody blood test; 3) Prescribed by or in consultation with a neurologist or neuromuscular specialist; 4) Age ≥ 6 years; 5) Documentation of a baseline clinical muscle strength assessment (e.g., QMG, 3TUG, T25FW); 6) Member does not have a history of seizures; 7) Request does not exceed health plan-approved quantity limit, if applicable; 8) Dose does not exceed: (a) adults and pediatrics ≥45 kg: 100 mg (10 tablets) per day; or (b) pediatrics <45 kg: 50 mg (5 tablets) per day.

Approval duration: 12 months

Continuation Therapy

Covered when ALL of the following are met for Continued Therapy (LEMS):

Continuation Therapy - LEMS: 1) Member is currently receiving medication via the Centene benefit or previously met initial approval criteria, or continuity of care provisions apply; 2) Member is responding positively to therapy as evidenced by clinical muscle strength assessments (e.g., QMG, 3TUG, T25FW); 3) Member does not have a history of seizures; 4) Request does not exceed health plan-approved quantity limit, if applicable; 5) If request is for a dose increase, the new dose does not exceed: (a) adults and pediatrics ≥45 kg: 100 mg (10 tablets) per day; or (b) pediatrics <45 kg: 50 mg (5 tablets) per day.

Approval duration: 12 months

Other Diagnoses/Indications

Other/Off-label uses:

Other diagnoses/indications: 1) If the drug has recently (within the last 6 months) undergone a label change not yet reflected in this policy, follow applicable formulary or non-formulary policies for the relevant line of business; OR 2) If the requested use (diagnosis, age, dosing) is not listed in section III (Diagnoses/Indications for which coverage is NOT authorized) and criterion 1 does not apply, refer to the off-label use policy for the relevant line of business (commercial, marketplace, or Medicaid).

See related policies CP.CPA.190, CP.CPA.09, CP.PMN.53 and line-of-business specific formulary/non-formulary policies

Coverage prerequisites and limits

Covered when consistent with Health Plan medical necessity criteria and member coverage documents

Coverage prerequisites: Member must have coverage under the Health Plan; therapy must meet medical necessity per this policy and any Health Plan-level administrative policies and procedures; request must not exceed health plan-approved quantity limits, if applicable.initial approval duration = 12 months

Decisions are subject to the terms, conditions, exclusions, and limitations of the member's coverage documents and applicable law/regulation.

Coverage for non-FDA approved (off‑label) indications is not authorized under this policy unless the request includes sufficient documentation of efficacy and safety in accordance with the applicable off‑label use policies. Refer to CP.CPA.09 for commercial lines of business, HIM.PA.154 for Health Insurance Marketplace, and CP.PMN.53 for Medicaid when submitting supporting evidence or rationale for an off‑label use.

When a conflict exists between this clinical policy and state Medicaid coverage provisions, the state Medicaid requirements take precedence. Providers must follow applicable state and federal requirements and any Health Plan‑level administrative policies and procedures that govern coverage and administration of benefits.

Use of amifampridine for non‑FDA approved indications is not authorized unless the submission contains documentation meeting the Health Plan's off‑label use criteria (see off‑label policies cited in this document). Requests lacking sufficient supporting evidence as required by those policies will not be approved.

The provided policy excerpts do not list additional explicit conditions that are labeled as 'not medically necessary.' Coverage decisions remain subject to the policy criteria, applicable exclusions (such as contraindications), and the member's benefit documents.

Coding and Dosing Information

Relevant drug codesNDC

NDC	Product NDCs as per prescribing information (not listed explicitly in this excerpt)

Affected codes (not specified)mixed

affected codes

referenced for prior authorization/coverage (document does not list specific CPT/HCPCS/NDC codes in this section)

Maximum daily dose — Adults and pediatrics

Adults & pediatrics ≥ 45 kgMaximum daily dose: 100 mg/day (10 tablets)

Pediatrics < 45 kgMaximum daily dose: 50 mg/day (5 tablets)

Maximum single dose (≥45 kg)Maximum single dose is 20 mg per dose

Maximum single dose (<45 kg)Maximum single dose is 10 mg per dose

Diagnostic CMAP increment

Diagnostic thresholdReproducible post-exercise increase in CMAP amplitude of at least 60% vs baseline

Provider Requirements and Administrative Actions

Prior Authorization

Prior Authorization Required

Prior authorization is required for Firdapse (amifampridine). Initial and continuation approvals are limited to 12 months. Requests must not exceed the health plan–approved quantity limits, if applicable, and dosing must not exceed the maximums specified in the policy (Adults and pediatrics ≥ 45 kg: 100 mg/day; Pediatrics < 45 kg: 50 mg/day).

Approval duration: 12 months for initial and continuation requests
Requests must not exceed health plan-approved quantity limit, if applicable
Maximum daily doses: Adults and pediatrics ≥ 45 kg = 100 mg/day; Pediatrics < 45 kg = 50 mg/day

Denial Risk

Denial-risk Criteria

Requests will be denied if the member has a history of seizures or hypersensitivity to amifampridine (or another aminopyridine). Requests that do not meet the diagnostic criteria for Lambert-Eaton Myasthenic Syndrome (LEMS) as specified in the policy will also be denied.

Background and Clinical Context

Lambert‑Eaton myasthenic syndrome (LEMS) is a presynaptic neuromuscular junction disorder characterized by impaired release of acetylcholine from motor nerve terminals. Firdapse (amifampridine) is a potassium channel blocker that enhances presynaptic calcium influx and increases acetylcholine release, thereby improving neuromuscular transmission in patients with LEMS. The drug is approved for the treatment of LEMS in patients aged ≥ 6 years and is dosed in divided administrations with maximum total daily limits dependent on body weight (100 mg/day for adults and pediatrics ≥ 45 kg; 50 mg/day for pediatrics < 45 kg). Diagnosis of LEMS is supported by electrophysiologic testing such as repetitive nerve stimulation demonstrating a reproducible post‑exercise increase in compound muscle action potential (CMAP) amplitude (increments of 60–99% are strongly supportive and >100% is diagnostic) or by positive anti‑P/Q‑type voltage‑gated calcium channel (VGCC) antibodies when RNS cannot be completed. Clinical response is documented using baseline and follow‑up muscle strength assessments (for example, QMG, 3TUG, or T25FW).

Definitions and Assessments

RNS — Repetitive Nerve Stimulation

RNS definitionRepetitive Nerve Stimulation testing showing reproducible post-exercise increase in CMAP amplitude; ≥60% increase meets diagnostic criteria for consideration

Supportive vs diagnostic incrementsIncrements 60–99% are strongly supportive; >100% after exercise or with high-frequency RNS is considered diagnostic

Alternate confirmatory testIf unable to complete RNS, positive anti-P/Q-type VGCC antibody blood test can be used

QMG / 3TUG / T25FW — Baseline clinical muscle strength assessments

Examples of baseline assessmentsQuantitative Myasthenia Gravis (QMG) score, triple-timed up-and-go (3TUG), Timed 25-foot Walk (T25FW)

QMG descriptionPhysician-rated evaluation of 13 muscle function assessments; scores 0–3 per item

Policy Summary

Payermhn

PolicyAmifampridine (Firdapse) for Lambert-Eaton Myasthenic Syndrome

Policy CodePolicy CP.PHAR.411

Change TypeAnnual review — material revisions

Effective DateJan 22, 2022

Next Review Date

Key ActionSubmit prior authorization with documentation that member meets all approval criteria, including baseline clinical muscle strength assessment.

SourceLink

On This Page

Increments of 60–99% are strongly supportive of a presynaptic neuromuscular junction disorder

Diagnostic range>100% increase after exercise or with high-frequency RNS is considered diagnostic

Initial approval duration

Initial approval duration12 months

Previous duration (revised)Previously 6 months; revised to 12 months during 1Q 2026 annual review

Approval noteApplies to initial (and continuation) prior authorization approvals per policy

Contraindications: history of seizures; hypersensitivity to amifampridine or another aminopyridine
Diagnostic requirements for LEMS include confirmatory testing (RNS showing ≥ 60% post-exercise CMAP increment or positive anti-P/Q VGCC antibody if RNS not possible)

Documentation Required

Provider must submit documentation (such as office chart notes, laboratory results, or other clinical information) that supports the member meets all applicable approval criteria.

Include confirmatory diagnostic test results (RNS or anti-P/Q VGCC antibody) when applicable
Include baseline and follow-up clinical muscle strength assessments (examples: QMG, 3TUG, T25FW)
Include specialist consult notes when treatment is prescribed by or in consultation with a neurologist or neuromuscular specialist

Note

Routing When Indication/Labeling Recently Changed

If the drug's indication or labeling has changed within the last 6 months and that change is not yet reflected in this policy, route the request per the formulary or non-formulary policies for the relevant line of business; if the requested use is not listed under excluded diagnoses/indications and the label change does not apply, route to the off-label use policy for the relevant line of business.

For formulary drugs: refer to no coverage criteria policies (CP.CPA.190 for commercial, HIM.PA.33 for marketplace, CP.PMN.255 for Medicaid)
For non-formulary drugs: refer to non-formulary policies (CP.CPA.190 for commercial, HIM.PA.103 for marketplace, CP.PMN.16 for Medicaid)
For off-label uses: refer to off-label use policies (CP.CPA.09 for commercial, HIM.PA.154 for marketplace, CP.PMN.53 for Medicaid)

Documentation Required

Documentation and Coverage Terms

Coverage decisions are subject to all terms, conditions, exclusions, and limitations of the member's coverage documents and applicable Health Plan-level administrative policies and procedures. Providers are responsible for following these administrative policies and documenting services in accordance with the member's coverage.

This clinical policy does not replace contract terms or state/federal requirements
Providers remain responsible for exercising professional medical judgment and for documentation consistent with health plan requirements
Where discrepancies exist between this policy and legal/regulatory requirements, law governs

3TUG & T25FW useFunctional mobility/walk tests used to quantify response to therapy (see Appendix D for methods)

Health Plan — definition

Health Plan definitionA health plan that has adopted this clinical policy and that is operated or administered, in whole or in part, by Centene Management Company, LLC, or any of such health plan's affiliates

ScopeApplies to the Health Plan's coverage decisions and administration of benefits

Document relationCoverage is subject to the terms, conditions, exclusions, and limitations of the member's coverage documents