CurrentNeighborhood Health Plan of Rhode IslandPolicy N/A

Carglumic acid (Carbaglu) coverage for NAGS deficiency, PA, MMA

Policy governs medical necessity and authorization criteria for coverage of carglumic acid (Carbaglu) for treatment of acute and chronic hyperammonemia due to N-acetylglutamate synthase (NAGS) deficiency and as adjunctive therapy for propionic acidemia (PA) or methylmalonic acidemia (MMA) for members within the plan scope.

Policy Summary

PayerNeighborhood Health Plan of Rhode Island

PolicyCarglumic acid (Carbaglu) coverage for NAGS deficiency, PA, MMA

Policy CodePolicy N/A

Change TypeNo material changes

Effective DateDec 1, 2020

Next Review DateN/A

Key ActionObtain prior authorization for up to 6 months when initial criteria are met and ensure documentation of baseline ammonia levels.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

6 monthstypical authorization duration for initial and continued therapy

NAGS, PA, MMAindications addressed

baseline ammoniarequired laboratory documentation

specialistprescriber requirement

Coverage Criteria

Trek Health ingests and normalizes Transparency in Coverage data and payer policy updates to give provider organizations a clear view of how commercial reimbursement behaves across markets, payers, and services. Our platform transforms raw payer disclosures into structured intelligence that supports contract evaluation, payer negotiations, and service line strategy. By combining market benchmarks with ongoing policy visibility, Trek helps teams identify variability, risk, and opportunity in commercial reimbursement. The result is faster insight, stronger negotiating positions, and more informed financial decisions.

Initial Approval — NAGS deficiency

Covered when ALL of the following are met:

Initial approval criteria for NAGS deficiency: 1) Confirmed diagnosis of N-acetylglutamate synthase (NAGS) deficiency; 2) Prescriber is a physician specializing in the patient’s diagnosis or the prescriber is in consultation with a physician experienced in metabolic disorders; 3) Documentation of baseline ammonia levels; 4) Initial and maintenance doses do not exceed FDA-approved labeling.

Authorization may be granted for 6 months if criteria are met; continued authorization may be granted for 6 months when the member is tolerating treatment and demonstrating clinical benefit (decrease in ammonia from baseline).

Initial Approval — PA or MMA

Covered when ALL of the following are met:

Initial approval criteria for PA/MMA: 1) Diagnosis of Methylmalonic Acidemia (MMA) or Propionic Acidemia (PA); 2) Prescriber is a physician specializing in the patient’s diagnosis of MMA or PA; 3) Dosing does not exceed FDA-approved labeling.

Authorization may be granted for 6 months if criteria are met; continued authorization may be granted for 6 months when the member is tolerating treatment and demonstrating benefit or disease stability.

All indications for carglumic acid (Carbaglu) other than treatment of acute or chronic hyperammonemia due to confirmed N-acetylglutamate synthase (NAGS) deficiency, or adjunctive treatment of acute hyperammonemia in propionic acidemia (PA) or methylmalonic acidemia (MMA), are considered experimental/investigational and are not a covered benefit.

Treatment of acute and chronic hyperammonemia due to confirmed NAGS deficiency; adjunctive treatment of acute hyperammonemia in PA and MMA.

Primary covered indications: Treatment of acute and chronic hyperammonemia due to confirmed NAGS deficiency; adjunctive treatment of acute hyperammonemia in PA and MMA.

During acute hyperammonemic episodes, concomitant administration with other ammonia-lowering therapies (alternate pathway medications, hemodialysis, and dietary protein restriction) is recommended. Authorization periods are typically 6 months for initial and continued therapy when criteria are met.

Provider Actions & Requirements

Prior Authorization

Prior Authorization Required

Prior authorization is required. An authorization may be granted for up to 6 months when initial criteria are met. Reauthorization may be granted for 6 months if the member meets initial criteria, is tolerating treatment, and demonstrates benefit (e.g., decreased ammonia from baseline for NAGS deficiency or disease stability/improvement for PA/MMA).

Initial authorization: up to 6 months
Reauthorization: up to 6 months with documentation of tolerance and clinical benefit (decrease in ammonia for NAGS; stability or improvement for PA/MMA)

Note

Concomitant Therapies

During acute hyperammonemic episodes, concomitant administration of Carbaglu (carglumic acid) with other ammonia-lowering therapies is recommended. This may include alternate pathway medications, hemodialysis, and dietary protein restriction. For maintenance therapy in NAGS deficiency, concomitant use of other ammonia-lowering therapies and protein restriction may be needed based on plasma ammonia levels.

Concomitant therapies during acute episodes: alternate pathway medications, hemodialysis, dietary protein restriction
Maintenance: consider concurrent ammonia-lowering therapies and protein restriction guided by plasma ammonia

Documentation Required

Required Documentation

Documentation required for prior authorization includes a confirmed diagnosis (NAGS deficiency, PA, or MMA as applicable), baseline ammonia levels, and dosing that aligns with FDA-approved labeling. For reauthorization, provide evidence of clinical response or disease stability/improvement and documentation that the patient is tolerating therapy.

Required: confirmed diagnosis (NAGS deficiency, Propionic Acidemia, or Methylmalonic Acidemia)
Required: baseline ammonia levels documented
Required: dosing consistent with FDA-approved labeling
Reauthorization: documentation of tolerance and clinical benefit

Documentation Required

Prescriber Specialty Requirement

Prescriptions should be written by a physician specializing in the patient’s diagnosis or by a prescriber working in consultation with a physician experienced in metabolic disorders.

Prescriber must be specialist in diagnosis or in consultation with a physician experienced in metabolic disorders

Denial Risk

Excluded Indications

Indications beyond treatment of acute or chronic hyperammonemia due to NAGS deficiency, and adjunctive treatment of acute hyperammonemia in Propionic Acidemia (PA) or Methylmalonic Acidemia (MMA), are considered experimental/investigational and are not covered benefits.

Covered: acute and maintenance hyperammonemia due to NAGS deficiency
Covered: adjunctive therapy for acute hyperammonemia in PA and MMA
Not covered: any other indications (experimental/investigational)

Background

Carglumic acid (Carbaglu) is indicated as an adjunctive therapy for the treatment of acute hyperammonemia due to deficiency of the hepatic enzyme N-acetylglutamate synthase (NAGS) in pediatric and adult patients, and for maintenance therapy of chronic hyperammonemia in NAGS deficiency when clinically appropriate. During acute hyperammonemic episodes, concomitant administration with other ammonia-lowering therapies (for example, alternate pathway medications, hemodialysis, and dietary protein restriction) may be recommended.

Carbaglu is also indicated as adjunctive therapy to standard of care for the treatment of acute hyperammonemia in patients with Propionic Acidemia (PA) or Methylmalonic Acidemia (MMA). Authorization for initial and continued treatment may be granted for up to 6 months when criteria are met and the patient is tolerating therapy with evidence of clinical benefit or disease stability.

Definitions

NAGS deficiency — definition and diagnostic context

DefinitionDeficiency of the hepatic enzyme N-acetylglutamate synthase (NAGS) causing acute or chronic hyperammonemia

Indication for therapyCarglumic acid (Carbaglu) is indicated as adjunctive therapy for acute hyperammonemia and for maintenance of chronic hyperammonemia in patients with confirmed NAGS deficiency

Diagnostic contextRequires a confirmed diagnosis of NAGS deficiency prior to authorization

Acute-management contextDuring acute hyperammonemic episodes, concomitant ammonia‑lowering therapies (alternate pathway medications, hemodialysis, dietary protein restriction) may be required

OpenPayer

Carglumic acid (Carbaglu) coverage for NAGS deficiency, PA, MMA

Coverage Criteria

Authorization & Coding

Provider Actions & Requirements

Background

Definitions

Not Covered