CurrentNeighborhood Health Plan of Rhode IslandPolicy N/A

Carglumic acid (Carbaglu) — coverage criteria for hyperammonemia

Covers clinical criteria, documentation, and authorization requirements for use of carglumic acid (Carbaglu) to treat acute and chronic hyperammonemia due to NAGS deficiency, and for hyperammonemia associated with propionic acidemia (PA) or methylmalonic acidemia (MMA). Applies to members for whom the medication is being requested.

Policy Summary

PayerNeighborhood Health Plan of Rhode Island

PolicyCarglumic acid (Carbaglu) — coverage criteria for hyperammonemia

Policy CodePolicy N/A

Change TypeNo material changes

Effective DateN/A

Next Review DateN/A

Key ActionSubmit enzyme assay, biochemical or genetic test results and baseline plasma ammonia levels with initial prior authorization requests.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

12 monthsauthorization duration (initial and reauthorization)

3FDA-approved indications listed

requiredbaseline plasma ammonia lab required

lab evidencediagnosis confirmation

Coverage Criteria for Carglumic Acid (Carbaglu)

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NAGS deficiency — initial coverage

Covered when ALL of the following are met for NAGS deficiency:

Diagnosis confirmation: Diagnosis is confirmed by enzymatic, biochemical, or genetic testing.

See documentation requirements for initial requests.

Baseline ammonia: Member has elevated plasma ammonia levels at baseline.

Baseline plasma ammonia must be documented in initial request.

PA/MMA — initial coverage

Covered when ALL of the following are met for acute hyperammonemia due to PA or MMA:

Indication: Acute hyperammonemia due to propionic acidemia (PA) or methylmalonic acidemia (MMA) as adjunctive therapy to standard of care.

Carbaglu is indicated as adjunctive therapy to standard of care during acute hyperammonemic episodes.

Reauthorization criteria

Reauthorization covered when one of the following is met:

NAGS reauthorization: Member is experiencing benefit from therapy as evidenced by a decrease in ammonia levels from baseline.

Authorization of 12 months may be granted for continued treatment when benefit is demonstrated.

PA or MMA reauthorization: Member is experiencing benefit as evidenced by disease stability or disease improvement for methylmalonic acidemia or propionic acidemia.

Authorization of 12 months may be granted for continued treatment when benefit is demonstrated.

All uses of carglumic acid (Carbaglu) outside the FDA‑approved indications — acute or chronic hyperammonemia due to NAGS deficiency and acute hyperammonemia due to propionic acidemia (PA) or methylmalonic acidemia (MMA) — are considered experimental/investigational and not medically necessary.

Use of carglumic acid for indications not listed in the FDA‑approved indications (NAGS deficiency, PA, MMA) is considered not medically necessary / investigational and will not be approved.

Confirmation of NAGS deficiency by genetic testing as part of diagnostic documentation for coverage of carglumic acid.

Confirmation of NAGS deficiency by genetic testing may be used as part of the diagnostic documentation required for coverage of carglumic acid.

Acceptable diagnostic tests: Diagnosis may be confirmed by genetic testing, enzymatic assay, or biochemical testing.

Enzyme assay, biochemical or genetic testing results are required for initial prior authorization review.

Provider Actions and Authorization Requirements

Prior Authorization

Prior authorization — 12-month approvals when criteria met

Authorization of up to 12 months may be granted when the coverage criteria for the indicated disorder are met (NAGS deficiency, methylmalonic acidemia, or propionic acidemia). For NAGS deficiency, approval requires confirmation of the diagnosis and elevated baseline plasma ammonia.

Step Therapy

Use Carbaglu adjunctively during acute episodes

During acute hyperammonemic episodes, Carbaglu must be used adjunctively with other ammonia‑lowering therapies (for example, alternate pathway medications, hemodialysis, and dietary protein restriction) as clinically indicated.

Adjunctive use with alternate pathway medications
Consider hemodialysis when indicated
Implement dietary protein restriction as appropriate

Documentation Required

Required documentation for initial and continuation requests

Initial prior authorization requests must include enzyme assay, biochemical, or genetic testing results that support a diagnosis of NAGS deficiency and laboratory results documenting baseline plasma ammonia levels; continuation requests must include lab results demonstrating a reduction in plasma ammonia from baseline.

Initial: enzyme assay, biochemical or genetic testing results supporting NAGS diagnosis
Initial: lab results documenting baseline plasma ammonia
Continuation: lab results showing reduction in plasma ammonia from baseline

Denial Risk

Non‑approved indications considered experimental/investigational

Requests for use of Carbaglu for indications other than the FDA‑approved indications (NAGS deficiency, PA, MMA) are considered experimental/investigational and not medically necessary.

Definitions and Diagnostic Confirmation

Confirmed diagnosis — acceptable tests for NAGS deficiency

Accepted confirmation methodsDiagnosis must be confirmed by enzymatic, biochemical, or genetic testing for NAGS deficiency.

Initial request evidenceInclude enzyme assay, biochemical, or genetic testing results supporting the diagnosis with the initial prior authorization submission.

Role in coverageConfirmed diagnosis is a required criterion for coverage of carglumic acid for NAGS deficiency.

Relation to other indicationsConfirmation by testing differentiates FDA‑approved NAGS indication from other non‑approved uses that are investigational/not medically necessary.

Background on Carglumic Acid (Carbaglu)

Carglumic acid (Carbaglu) is indicated as adjunctive therapy during acute hyperammonemic episodes and as maintenance therapy for chronic hyperammonemia due to N‑acetylglutamate synthase (NAGS) deficiency. During acute episodes, Carbaglu should be used in combination with standard ammonia‑lowering interventions (for example, alternate pathway medications, hemodialysis, and dietary protein restriction) as clinically indicated. It is also indicated as adjunctive therapy for acute hyperammonemia associated with propionic acidemia (PA) or methylmalonic acidemia (MMA).