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Ammonul (Sodium Phenylacetate / Sodium Benzoate) - Indications and Dosage



AMMONUL® is indicated as adjunctive therapy for the treatment of acute hyperammonemia and associated encephalopathy in patients with deficiencies in enzymes of the urea cycle. In acute neonatal hyperammonemic coma, in moderate to severe episodes of hyperammonemic encephalopathy, and in episodes of hyperammonemia which fail to respond to an initial course of AMMONUL® therapy, hemodialysis is the most rapid and effective technique for removing ammonia [12,13]. In such cases, the concomitant administration of AMMONUL® can help prevent the re-accumulation of ammonia by increasing waste nitrogen excretion [4,5,13].


Administration must be through a central line. Administration through a peripheral line may cause burns.


AMMONUL® is administered intravenously as a loading dose infusion administered over 90 to 120 minutes, followed by an equivalent maintenance dose infusion administered over 24 hours. AMMONUL® may not be administered by any other route. Administration of analogous oral drugs, such as Buphenyl® (sodium phenylbutyrate), should be terminated prior to AMMONUL® infusion.

Hyperammonemic coma (regardless of cause) in the newborn infant should be aggressively treated while the specific diagnosis is pursued. All patients should be promptly hemodialyzed as the procedure of choice using the largest catheters consistent with the patient's size. A target blood flow of 150 mL/min/m2 may be attained using a 7F catheter. (Ammonia clearance [mL/min] is similar to the blood flow rate [mL/min] through the dialyzer). Clearance of ammonia is approximately ten times greater by hemodialysis than by peritoneal dialysis or hemofiltration. Exchange transfusion is ineffective in the management of hyperammonemia. Hemodialysis may be repeated until the plasma ammonia level is stable at normal or near normal levels.

AMMONUL® infusion should be started as soon as the diagnosis of hyperammonemia is made. Treatment of hyperammonemia also requires caloric supplementation and restriction of dietary protein. Non-protein calories should be supplied principally as glucose (8–10 mg/kg/min) with Intralipid added. Attempts should be made to maintain a caloric intake of greater than 80 cal/kg/d. During and after infusion of AMMONUL®, ongoing monitoring of neurological status, plasma ammonia levels, clinical laboratory values, and clinical responses are crucial to assess patient response to treatment. The need for other interventions to control hyperammonemia must be considered throughout the course of treatment. Patients with a large ammonia burden or who are not responsive to AMMONUL® administration require aggressive therapy including hemodialysis (see WARNINGS).

AMMONUL® must be diluted with sterile Dextrose Injection, 10% (D10W) before administration. The dilution and dosage of AMMONUL® are determined by weight for neonates, infants and young children, and by body surface area for larger patients, including older children, adolescents, and adults (Table 3). Maintenance infusions may be continued until elevated plasma ammonia levels have been normalized or the patient can tolerate oral nutrition and medications.

AMMONUL® solutions are physically and chemically stable for up to 24 hours at room temperature and room lighting conditions. No compatibility information is presently available for AMMONUL® infusion solutions except for Arginine HCl Injection, 10%, which may be mixed in the same container as AMMONUL®. Other infusion solutions and drug products should not be administered together with AMMONUL® infusion solution. AMMONUL® solutions may be prepared in glass and PVC containers. AMMONUL® solutions should be inspected visually for particulate matter and discoloration before administration.

Table 3 Dosage and Administration
Patient PopulationComponents of Infusion Solution
AMMONUL® must be diluted with sterile dextrose injection 10% at ≥ 25 mL/Kg before administration.
Dosage Provided
AMMONUL®Arginine HCl Injection, 10%Sodium PhenylacetateSodium BenzoateArginine HCl
0 to 20 kg:
CPS and OTC Deficiency
Loading: over 90 to 120 minutes2.5 mL/kg2.0 mL/kg250 mg/kg250 mg/kg200 mg/kg
Maintenance: over 24 hours
ASS and ASL Deficiency
Loading: over 90 to 120 minutes2.5 mL/kg6.0 mL/kg250 mg/kg250 mg/kg600 mg/kg
Maintenance: over 24 hours
> 20 kg:
CPS and OTC Deficiency
Loading: over 90 to 120 minutes55 mL/m22.0 mL/kg5.5 g/m25.5 g/m2200 mg/kg
Maintenance: over 24 hours
ASS and ASL Deficiency
Loading: over 90 to 120 minutes55 mL/m26.0 mL/kg5.5 g/m25.5 g/m2600 mg/kg
Maintenance: over 24 hours

Arginine Administration

Intravenous arginine is an essential component of therapy for patients with carbamyl phosphate synthetase (CPS), ornithine transcarbamylase (OTC), argininosuccinate synthetase (ASS), or argininosuccinate lyase (ASL) deficiency. Because a hyperchloremic acidosis may ensue after high-dose arginine hydrochloride administration, plasma levels of chloride and bicarbonate should be monitored and appropriate amounts of bicarbonate administered.

Pending a specific diagnosis, intravenous arginine (6 mL/kg of Arginine HCl Injection, 10%, over 90 minutes followed by the same dose over 24 hours) should be given to hyperammonemic infants suspected of having a urea cycle disorder for two reasons: 1) infants with deficiencies in enzymes of the urea cycle (apart from arginase deficiency) are usually arginine-deficient; 2) hyperammonemia in infants with ASS or ASL deficiency usually respond favorably to arginine administration. If deficiencies of ASS or ASL are excluded as diagnostic possibilities, the intravenous dose of arginine HCl should be reduced to 2 mL/kg/d Arginine HCl Injection, 10%.

Converting To Oral Treatment

Once elevated ammonia levels have been reduced to the normal range, oral therapy, such as sodium phenylbutyrate, dietary management and protein restrictions should be started or reinitiated.


AMMONUL® (sodium phenylacetate and sodium benzoate) Injection 10% / 10% is supplied in single-use glass vials.

NDC-62592-720-50 single use vial containing 50 mL of sodium phenylacetate and sodium benzoate injection 10% / 10%.

Storage: Store at 25°C (77°F), excursions permitted to 15°– 30°C (59°– 86°F).



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