Sodium phenylbutyrate is used in adults and children to treat urea cycle disorders.

Sodium phenylbutyrate can be used with other medicines and may also include changes in diet.

Sodium phenylbutyrate may also be used for purposes not listed in this medication guide.

Use only as directed. Tell your doctor if you use other medicines or have other medical conditions or allergies.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

You may need to follow a special diet. Follow all instructions of your doctor or dietitian. Learn about the foods you should eat or avoid.

Wear a medical alert tag or carry an ID card to let others know you have a urea cycle disorder.

Doses are based on weight. Your dose may change if you gain or lose weight.

Take sodium phenylbutyrate with food.

Shake the oral powder lightly before mixing it with food.

Measure the dose of sodium phenylbutyrate oral pellets with the supplied measuring device (not a kitchen spoon).

Swallow sodium phenylbutyrate oral pellets immediately with soft food, such as applesauce, or water, fruit juices, or protein-free infant formulas. Do not chew or mix into liquids.

Do not give or take sodium phenylbutyrate oral suspension and oral pellets through a gastrostomy or nasogastric tube

Your blood may need to be tested often.

Store at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use. Throw away any remaining oral pellets 45 days after first opening the bottle.

Usual Adult Dose for Urea Cycle Disorders:

Administer orally in equally divided doses with each meal or feeding (i.e., 3 to 6 times a day):
-Weight: Less than 20 kg: 450 to 600 mg/kg/day
-Weight: 20 kg or Greater: 9.9 to 13 g/m2/day

Comments:
-Treatment should be combined with dietary protein restriction and, in some cases, essential amino acid
supplementation.

Uses:
-Adjunctive therapy in the chronic management of urea cycle disorders (UCDs) involving deficiencies of carbamylphosphate synthetase, ornithine transcarbamylase, or argininosuccinic acid synthetase.
-Indicated for treatment of neonatal-onset deficiency (complete enzymatic deficiency, presenting within the first 28 days of life) and late-onset disease (partial enzymatic deficiency, presenting after the first month of life) with history of hyperammonemic encephalopathy.

Usual Pediatric Dose for Urea Cycle Disorders:

Administer orally in equally divided doses with each meal or feeding (i.e., 3 to 6 times a day):
-Weight: Less than 20 kg: 450 to 600 mg/kg/day
-Weight: 20 kg or Greater: 9.9 to 13 g/m2/day

Comments:
-Treatment should be combined with dietary protein restriction and, in some cases, essential amino acid
supplementation.
-Tablets are not recommended in patients weighing less than 20 kg.

Uses:
-Adjunctive therapy in the chronic management of UCDs involving deficiencies of carbamylphosphate synthetase, ornithine transcarbamylase, or argininosuccinic acid synthetase.
-Indicated for treatment of neonatal-onset deficiency (complete enzymatic deficiency, presenting within the first 28 days of life) and late-onset disease (partial enzymatic deficiency, presenting after the first month of life) with history of hyperammonemic encephalopathy.

Sodium phenylbutyrate should not be used to treat immediate symptoms of an ammonia build-up.

Tell your doctor if you have:

• heart problems;

• high blood pressure;

• diabetes or a history of fructose intolerance, glucose-galactose malabsorption, or sucrase-isomaltase deficiency (sodium phenylbutyrate oral pellet contains sucrose); or

• liver or kidney disease.

Tell your doctor if you are pregnant or breastfeeding.

Oral pellet: Use the medicine as soon as you can, but skip the missed dose if your next dose is due in less than 3 hours. Do not use two doses at one time.

Oral suspension, tablets, powder: Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Sodium phenylbutyrate may cause serious side effects. Call your doctor at once if you have:

• nervous system problems-- sleepiness, tiredness, feeling light-headed, vomiting, nausea, headache, confusion;

• low blood potassium--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling;

• heart problems--swelling, rapid weight gain, feeling short of breath; or

• signs of infection--fever, chills, sore throat, body aches, unusual tiredness, loss of appetite, bruising or bleeding.

Common side effects of sodium phenylbutyrate may include:

• missed menstrual periods or changes in your menstrual periods;

• loss of appetite;

• change in body odor; or

• unusual or unpleasant taste in your mouth.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your doctor about all your other medicines, especially:

• steroids;

• haloperidol;

• valproic acid; or

• probenecid.

This list is not complete. Other drugs may affect sodium phenylbutyrate, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible drug interactions are listed here.