CurrentNeighborhood Health Plan of Rhode IslandPolicy 2121-A

Sodium phenylbutyrate (Buphenyl/Olpruva/Pheburane) for urea cycle disorders — Prior authorization and coverage criteria

Covers prior authorization, documentation, and clinical criteria for sodium phenylbutyrate products (Buphenyl, Olpruva, Pheburane, generic) used as adjunctive chronic management of urea cycle disorders for members of Neighborhood Health Plan of Rhode Island.

Policy Summary

PayerNeighborhood Health Plan of Rhode Island

PolicySodium phenylbutyrate (Buphenyl/Olpruva/Pheburane) for urea cycle disorders

Policy CodePolicy 2121-A

Change TypeNo material change

Effective Date

Next Review Date

Key ActionSubmit enzyme assay, biochemical or genetic test results and baseline plasma ammonia for initial authorization; include lab evidence of ammonia reduction for continuation.

SourceLink

POLICY UPDATE CHANGES

No material clinical or coverage changes in this revision.

12authorization duration (months)

3FDA-indicated enzymes

≥20 kg / BSA ≥1.2Olpruva threshold

baseline + reductionrequired lab documentation

Coverage Criteria

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Initial Approval Criteria

Covered when ALL of the following are met:

Initial approval general: Diagnosis of a urea cycle disorder confirmed by enzymatic, biochemical, or genetic testing.

Initial approval general: Member has elevated plasma ammonia levels at baseline.baseline elevated ammonia

Olpruva-specific: For Olpruva requests, patient must weigh ≥ 20 kg AND have body surface area (BSA) ≥ 1.2 m².weight >= 20 kg; BSA >= 1.2 m2

Applies only to Olpruva formulations

Authorization duration: Authorization may be granted for 12 months for initial approval when the above criteria are met.

Continuation Criteria

Covered for continuation when ALL of the following are met:

Continuation benefit: Member is experiencing benefit from therapy as evidenced by a documented reduction in plasma ammonia levels from baseline.documented reduction in plasma ammonia

Lab documentation is required for reauthorization.

Authorization duration: Continuation authorization may be granted for 12 months when the above condition is satisfied.

All indications for sodium phenylbutyrate products that are not specifically listed as FDA-approved indications or the compendial indication for arginase deficiency are considered experimental/investigational and not medically necessary.

Uses of sodium phenylbutyrate beyond the FDA-approved indications and the compendial use for arginase deficiency are explicitly listed as not medically necessary and will not be covered.

Provider Actions & Authorization

Prior Authorization

Prior Authorization Required

Prior authorization is required for treatment. Approvals (initial and continuation) may be granted for up to 12 months when the clinical criteria are met.

Authorization duration: up to 12 months for both initial and continuation requests when criteria are met.

Note

Provider Action

Preserve any operational or provider-facing notes from the source; providers should follow standard prior authorization submission processes and contact the plan for questions about requests.

Documentation Required

Required Documentation

Required documentation must be submitted with the request to initiate review for both initial and continuation authorizations.

Initial requests: enzyme assay, biochemical, or genetic testing results supporting the diagnosis.
Initial requests: laboratory results documenting baseline plasma ammonia levels.
Continuation requests: laboratory results documenting a reduction in plasma ammonia levels from baseline.

Denial Risk

Denial Triggers

Requests that are missing required diagnostic confirmation, baseline labs, or evidence of benefit (for continuation) will be denied. Exclusions or failure to meet specific product criteria will also result in non-coverage.

Missing enzymatic, biochemical, or genetic test results to confirm diagnosis.
Missing baseline plasma ammonia lab results for initial requests.
For continuation requests: missing documentation of reduction in plasma ammonia from baseline.
Requests that do not meet product-specific criteria (e.g., Olpruva requests not meeting weight and BSA requirements) will be denied.

Background

Urea cycle disorders (UCDs) are inborn errors of metabolism caused by deficiencies of one of the urea cycle enzymes (for example, carbamoyl phosphate synthetase, ornithine transcarbamylase, argininosuccinate synthetase, or arginase), resulting in impaired conversion of ammonia to urea and risk of life‑threatening hyperammonemia. Sodium phenylbutyrate preparations are used as adjunctive therapy to dietary management to reduce plasma ammonia levels in chronic management of UCDs. Acute hyperammonemia remains a medical emergency and requires immediate treatment beyond chronic adjunctive therapy.