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sodium phenylacetate/sodium benzoate(soe-dee-um fen-il-as-e-tate/soe-dee-um ben-zo-ate) ,
Pharmacologic: none assigned
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.
Provides an alternative pathway for nitrogen elimination in patients without a fully functioning urea cycle.
Decreased sequelae of hyperammonemia including encephalopathy and death.
Absorption: IV administration results in complete bioavailability.
Metabolism and Excretion: Metabolized in the liver as part of the alternative pathway in the urea cycle; also metabolized in the kidney.
Time/action profile (blood levels)
|IV||rapid||1–3 hr||14–26 hr|
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
Fluid and Electrolyte
Drug-Drug interactionPenicillin and probenecid may compete for renal secretion.Valproic acid may contribute to hyperammonemia and negate beneficial effects.
Route/DosageConcurrent 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.
Solution for injection (requires dilution): sodium phenylacetate 10% and sodium benzoate injection 10% in 50–mL vials
- 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 DiagnosesRisk for injury (Indications)
- 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.
- 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.
- Explain purpose of medication to parents/caregivers.
- Decreased sequelae of hyperammonemia including encephalopathy and death.