sodium phenylacetate

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sodium phenylacetate/sodium benzoate

(soe-dee-um fen-il-as-e-tate/soe-dee-um ben-zo-ate) ,

Ammonul

(trade name)

Classification

Therapeutic: antidotes
Pharmacologic: none assigned

Indications

Adjunctive therapy of acute hyperammonemia associated with urea cycle disorders; when lack of specific enzymes results in an inability to breakdown and eliminate waste nitrogens.

Action

Provides an alternative pathway for nitrogen elimination in patients without a fully functioning urea cycle.

Therapeutic effects

Decreased sequelae of hyperammonemia including encephalopathy and death.

Pharmacokinetics

Absorption: IV administration results in complete bioavailability.
Distribution: Unknown.
Metabolism and Excretion: Metabolized in the liver as part of the alternative pathway in the urea cycle; also metabolized in the kidney.
Half-life: Unknown.

Time/action profile (blood levels)

ROUTEONSETPEAKDURATION
IVrapid1–3 hr14–26 hr

Contraindications/Precautions

Contraindicated in: Hypersensitivity.
Use Cautiously in: Hepatic/renal impairment; Obstetric: Use only if clearly needed; Lactation: Safety not established.

Adverse Reactions/Side Effects

Central nervous system

  • seizures (life-threatening)
  • mental impairment

Gastrointestinal

  • vomiting

Endocrinologic

  • hyperglycemia

Fluid and Electrolyte

  • hypokalemia

Interactions

Drug-Drug interaction

Penicillin and probenecid may compete for renal secretion.Valproic acid may contribute to hyperammonemia and negate beneficial effects.

Route/Dosage

Concurrent IV arginine is required.
Intravenous (Children 0–20 kg) Loading dose over 90–120 min—2.5 mL/kg (provides 250 mg/kg of sodium phenylacetate and 250 mg/kg sodium benzoate) followed by maintenance infusion—2.5 mL/kg (provides 250 mg/kg of sodium phenylacetate and 250 mg/kg sodium benzoate) over 24 hr, continued until oral therapy is initiated.
Intravenous (Children >20 kg) Loading dose over 90–120 min—2.5 mL/kg (provides 250 mg/kg of sodium phenylacetate and 250 mg/kg sodium benzoate) followed by maintenance infusion—55 mL/m2(provides 5.5 g/m2 of sodium phenylacetate and 5.5 g/m2 sodium benzoate) over 24 hr, continued until oral therapy is initiated.

Availability

Solution for injection (requires dilution): sodium phenylacetate 10% and sodium benzoate injection 10% in 50–mL vials

Nursing implications

Nursing assessment

  • Assess neurologic status frequently during therapy.
  • Assess infusion site frequently during therapy. Extravasation into peripheral tissues may lead to skin necrosis. If extravasation is suspected, discontinue infusion and resume at a different site. Treatment of extravasation may include aspiration of residual drug from catheter, limb elevation, and intermittent cooling using cold packs.
  • Lab Test Considerations: Monitor plasma ammonia levels frequently during therapy.
    • Monitor CBC and serum electrolytes frequently during therapy; maintain normal levels. May cause hyperglycemia, hypocalcemia, hypokalemia, and anemia.
    • Monitor blood chemistry, pH, and pCO2 frequently during therapy. May cause metabolic acidosis and hyperammonemia.

Potential Nursing Diagnoses

Risk for injury (Indications)

Implementation

  • Must be diluted and administered through a central line; administration through peripheral lines may cause burns.
    • May cause nausea and vomiting; administer an antiemetic prior to infusion.
    • Do not repeat loading dose; phenylacetate plasma levels are prolonged.
    • Begin infusion as soon as the diagnosis of hyperammonemia is made.
    • Caloric supplementation and restriction of dietary protein are required during therapy. Caloric intake of >80 cal/kg/day should be attempted. Non-protein calories should be supplied as glucose (8–10 mg/kg/min) with Intralipid added.
    • Once elevated ammonia levels have been reduced to normal range, oral therapy, such as sodium phenylbutyrate, dietary management and protein restrictions should be started or reinitiated.
  • Intravenous Administration
  • Intermittent Infusion: Diluent: Dilute with D10W at ≥25 mL/kg before administration. Use a Millex Durapore GV 33 mm Sterile Syringe Filter (0.22 µm ) during the admixture process when injecting Ammonul into the 10% Dextrose IV bag, regardless of whether particulate matter is seen in the vial; particulate matter may not be seen on visual inspection. Solution is stable for 24 hr at room temperature. Do not administer solutions that are discolored or contain particulate matter.
  • Rate: Administer loading dose over 90–120 min.
  • Continuous Infusion: Diluent: Maintenance infusions use same dilution as loading dose and may be continued until elevated plasma ammonia levels have been normalized or patient can tolerate oral nutrition and medications.
  • Rate: Administer maintenance infusion over 24 hr.
  • Additive Compatibility: arginine 10%.
  • Additive Incompatibility: Do not mix or infusion other solutions or medications with sodium phenylacetate and sodium benzoate.

Patient/Family Teaching

  • Explain purpose of medication to parents/caregivers.

Evaluation/Desired Outcomes

  • Decreased sequelae of hyperammonemia including encephalopathy and death.
References in periodicals archive ?
Swedish Orphan Biovitrum (Sobi) (STO: SOBI) has entered a three-year agreement with Valeant Pharmaceuticals Ireland (NYSE: VRX) for the distribution of Ammonul (sodium phenyl acetate and sodium benzoate) injection in Europe, the Middle East and North Africa, the company announced on Tuesday.
The deal gives Sobi the exclusive rights and licence for sales and distribution of Ammonul for named patient use (NPU) programmes in Europe, the Middle East and North Africa until 31 December 2019.
Ammonul is not registered in the European Union, Middle East or North Africa and is only available under NPU programmes but it is approved by the US Food and Drug Administration (FDA) for the treatment of acute Urea Cycle Disorders (UCDs).
Biopharmaceutical company Hyperion Therapeutics Inc (NasdaqGM:HPTX) said on Thursday that it has exercised its option to acquire BUPHENYL (sodium phenylbutyrate) Tablets and Powder and AMMONUL (sodium phenylacetate and sodium benzoate) Injection 10%/10%.
AMMONUL (sodium phenylacetate and sodium benzoate) Injection 10%/10% is a hospital based product used to treat UCD patients in hyperammonemic crisis.