CurrentNeighborhood Health Plan of Rhode IslandPolicy 2121-A

Sodium Phenylbutyrate Products Sgm 2121 A P2025

Defines coverage, documentation, prescriber requirements, and authorization criteria for sodium phenylbutyrate products for treatment of urea cycle disorders (including arginase deficiency) and lists FDA-approved and compendial indications. Covers initial and continuation authorization criteria and duration.

Policy Summary

PayerNeighborhood Health Plan of Rhode Island

PolicySodium Phenylbutyrate Products Sgm 2121 A P2025

Policy CodePolicy 2121-A

Change TypeNo material change

Effective Date

Next Review Date

Key ActionSubmit enzyme assay, biochemical, or genetic testing results and lab results documenting baseline plasma ammonia levels for initial requests; submit lab results showing reduced plasma ammonia for reauthorization.

SourceLink

POLICY UPDATE CHANGES

No material clinical/coverage changes

3Named product variants

ArginaseCovered compendial indication

12Authorization duration (months)

Coverage Summary

This policy covers sodium phenylbutyrate products (Buphenyl, Olpruva, Pheburane) as adjunctive therapy for chronic management of urea cycle disorders (UCDs), including arginase deficiency, with an authorization duration of 12 months when criteria are met. Coverage is covered with criteria and requires documented diagnosis by enzymatic, biochemical, or genetic testing and baseline elevated plasma ammonia; requests for Olpruva additionally require the patient to meet the labeling thresholds of >= 20 kg weight and BSA >= 1.2 m2.

Covered Indications - Urea Cycle Disorders (including arginase deficiency)

Authorization of 12 months may be granted for chronic management when ALL of the following criteria are met:

ALL of the following

Diagnosis is confirmed by enzymatic, biochemical, or genetic testing
Member has elevated plasma ammonia levels at baseline
If the request is for Olpruva, ALL of the following must be met
- Patient weighs 20 kg or greater>= 20 kg
  Olpruva-specific weight threshold
- Patient has a body surface area (BSA) of 1.2 m2 or greater>= 1.2 m2
  Olpruva-specific BSA threshold

Referenced products: Covered products include Buphenyl, Olpruva, and Pheburane (sodium phenylbutyrate)

Initial Therapy Criteria

Initial Authorization — Urea Cycle Disorders (including arginase deficiency)

Authorization of 12 months may be granted for chronic management when ALL of the following criteria are met: (Initial authorization — 12 months)

Initial therapy criteria

Diagnosis is confirmed by enzymatic, biochemical, or genetic testing
Submit enzyme assay, biochemical, or genetic testing results supporting diagnosis
Member has elevated plasma ammonia levels at baseline
Submit lab results documenting baseline plasma ammonia levels
If the request is for Olpruva, ALL of the following must be met
- Patient weighs 20 kg or greater>= 20 kg
  Olpruva-specific weight threshold
- Patient has a body surface area (BSA) of 1.2 m2 or greater>= 1.2 m2
  Olpruva-specific BSA threshold

Referenced products: Covered products include Buphenyl, Olpruva, and Pheburane (sodium phenylbutyrate)

Continuation Therapy Criteria

Continuation of Therapy

Authorization of 12 months may be granted for continued treatment when ALL of the following are met:

Request is for an indication listed in the coverage criteria section

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

Submit lab results documenting a reduction in plasma ammonia levels from baseline

Provider Actions & Documentation Requirements

Prior Authorization

Prior authorization submission requirements - initial requests

For initial prior authorization, submit evidence confirming the diagnosis and baseline ammonia level. Provide enzyme assay, biochemical, or genetic testing results that support the urea cycle disorder diagnosis, and lab results documenting baseline plasma ammonia levels.

Enzyme assay results
Biochemical testing results
Genetic testing results
Lab results documenting baseline plasma ammonia levels

Prior Authorization

Prior authorization submission requirements - continuation requests

For continuation/reauthorization requests, submit laboratory documentation showing the member is benefiting from therapy. Provide lab results that document a reduction in plasma ammonia levels from the baseline value.

Documentation Required

Prescriber specialty requirement

Medication must be prescribed by, or in consultation with, a physician who specializes in the treatment of enzyme or metabolic disorders.

Clinical Evidence & References

Evidence includes package inserts and guideline/Genereviews citations: Buphenyl [package insert] (Oct 2024); Pheburane [package insert] (Aug 2023); Olpruva [package insert] (Dec 2022); sodium phenylbutyrate [package insert] (Jul 2017); GeneReviews and clinical guideline references (e.g., Mew & Lanpher GeneReviews 2017; Häberle et al. 2019). The Olpruva label restricts use to patients weighing 20 kg or greater and with a body surface area (BSA) of 1.2 m2 or greater.

Background

Sodium phenylbutyrate products are approved as adjunctive therapy for the chronic management of urea cycle disorders (UCDs), including deficiencies of CPS, OTC, or AS; they are indicated in neonatal-onset disease and late-onset disease with hyperammonemic encephalopathy. In neonatal-onset UCD, diagnosis should be made early and treatment initiated immediately because hyperammonemia is life‑threatening. The Olpruva product label specifically restricts use to patients >= 20 kg and with a BSA >= 1.2 m2.

Quick facts and thresholds

Olpruva weight>= 20 kg

Olpruva body surface area>= 1.2 m2

Authorization duration12 months

Named product variants3