Probenecid - known to inhibit the renal transport of many organic compounds, including hippuric acid, and may affect renal excretion of the conjugation product of sodium phenylbutyrate, as well as its metabolite.

Corticosteroids- may cause breakdown of body protein and increase plasma ammonia levels. Haloperidol/ Valproate- may cause hyperammonemia.

Urea cycle disorders

Abdominal pain, gastritis, nausea, vomting, constipation, rectal bleeding, peptic ulcer disease. Aplastic anemia, ecchymosis.

Arrhythmia, edema.

Depression, neurotoxicity, somnolence, fatigue and lightheadedness.

Headache, syncope, weight gain, renal tubular acidosis, rash.

Management of hyperammonemia, which is a medical emergency.

Special precautions:

Monitoring- maintain plasma levels of ammonia, arginine, branched chain amino acids and serum proteins within limits.

Indication:

Urea cycle disorders

Dosage:

Tablets- It is indicated for children weighing more than 20 kg.

Usual dose 450 to 600mg/kg/day in patients weighing less than 20kg, or 9.9 to 13g/m2/day in larger patients

Pharmacology:

Sodium phenylbutyrate is a pro-drug and is rapidly metabolised to phenylacetate. Phenylacetate is a metabolically active compound that conjugates with glutamine via acetylation to phenylacetylglutamine.

Pharmacokinetics:

Peak plasma levels of phenylbutyrate occur within 1 hr after a single dose of 5g sodium phenylbutyrate powder with a Cmax of 195mcg/ml and for the tablets a Cmax of 218mcg/ml under fasting conditions

Pregnancy:

Give Sodium phenylbutyrate to a pregnant woman, only if clearly needed.

Lactation:

Excercise caution while administering sodium phenylbutyrate to a nursing woman.