sodium phenylacetate/sodium benzoate

REMS

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.

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity.

Use Cautiously in:

Hepatic impairment;
Renal impairment;
OB: Safety not established in pregnancy;
Lactation: Safety not established in breastfeeding.

Adv. Reactions/Side Effects ⬆ ⬇

Endo: hyperglycemia

GI: vomiting

F and E: hypokalemia

Neuro: mental impairment, SEIZURES

Interactions ⬆ ⬇

Drug-drug:

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

Availability ⬆ ⬇

(Generic available)

Solution for injection: sodium phenylacetate 100 mg + sodium benzoate 100 mg/mL

Route/Dosage ⬆ ⬇

Concurrent IV arginine is required.
IV (Children 0–20 kg): Loading dose: 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.
IV (Children >20 kg): Loading dose: 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.

US Brand Names ⬆ ⬇

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.

Classifications ⬆ ⬇

Therapeutic Classification: antidotes

Pharmacologic Classification: none assigned

Pharmacokinetics ⬆ ⬇

Absorption: IV administration results in complete bioavailability.

Distribution: Unknown.

Metabolism/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 ⬆ ⬇

(plasma concentrations)

ROUTE	ONSET	PEAK	DURATION
IV	rapid	1–3 hr	14–26 hr

Patient/Family Teaching ⬆ ⬇

Explain purpose and side effects of medication to patient.
Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult health care professional before taking other medications.
Advise patient of adverse reactions such as vomiting, hyperglycemia, hypokalemia, convulsions, and mental impairment.
Instruct patient that when plasma ammonia levels normalize, dietary protein intake can be ↑ with the goal of unrestricted protein intake.
Rep: Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected or if breastfeeding.

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Indications ⬇