Sodium phenylbutyrate

What is sodium phenylbutyrate?

Sodium phenylbutyrate is converted to a substance in the body that helps the kidneys eliminate waste substances from the body. These waste substances can produce ammonia, which is toxic if it builds up in your blood.

Sodium phenylbutyrate is used to treat urea cycle disorders in people who lack certain liver enzymes needed to properly eliminate waste substances from the body. sodium phenylbutyrate helps prevent a build-up of ammonia in the blood.

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

Important Information

Seek emergency medical attention if you notice any signs of ammonia build-up, including mood or behavior changes, memory loss, thinking problems, muscle twitching, back and forth movement of the eyes, vomiting, increasing weakness, slurred speech, seizure (convulsions), and fainting.

Sodium phenylbutyrate will not treat immediate symptoms of an ammonia build-up.

Before Taking Sodium phenylbutyrate

You should not use sodium phenylbutyrate if you are allergic to it. sodium phenylbutyrate will not treat immediate symptoms of an ammonia build-up.

To make sure sodium phenylbutyrate is safe for you, tell your doctor if you have:

• congestive heart failure;

• high blood pressure;

• severe kidney disease;

• swelling or fluid retention; or

• epilepsy or other seizure disorder.

FDA pregnancy category C. It is not known whether sodium phenylbutyrate will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medicine.

It is not known whether sodium phenylbutyrate passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

Do not give this medicine to a child who weighs less than 44 pounds unless your doctor tells you to.

How should I take sodium phenylbutyrate?

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Take this medicine with each meal. Divide your total daily dose among all of your meals for the day.

Sodium phenylbutyrate powder should be mixed with food before consuming.

Shake the powder lightly before mixing it with food.

Use sodium phenylbutyrate regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely. You may need to take this medicine for the rest of your life.

Call your doctor right away if you have any signs of infection such as fever, chills, redness, swelling, body aches, or weakness. An infection may cause your condition to go out of control even while you are taking sodium phenylbutyrate.

While using sodium phenylbutyrate, you may need frequent blood tests.

Sodium phenylbutyrate is only part of a treatment program that may also include diet, dialysis, and other medications. Follow your doctor's instructions very closely.

Keep using this medicine even if you feel well. Your condition may have no symptoms. If the urea cycle disorder is not under control, you may have a build-up of ammonia, which can cause life-threatening side effects.

Store at room temperature away from moisture and heat. Keep the bottle tightly closed when not in use.

What happens if I miss a dose of Sodium phenylbutyrate?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

Be sure to take sodium phenylbutyrate with food.

What happens if I overdose?

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

What should I avoid while taking sodium phenylbutyrate?

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

Sodium phenylbutyrate side effects

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

Even with treatment, urea cycle disorders can cause a build-up of ammonia in the blood which can result in life-threatening side effects. Seek emergency medical attention if you notice any signs of ammonia build-up, including mood or behavior changes, memory loss, thinking problems, muscle twitching, back and forth movement of the eyes, vomiting, increasing weakness, slurred speech, seizure (convulsions), and fainting.

Call your doctor at once if you have:

• severe drowsiness, confusion;

• swelling, rapid weight gain;

• a light-headed feeling, like you might pass out; or

• pale skin, feeling short of breath, rapid heart rate.

Common side effects may include:

• missed menstrual periods, changes in your regular cycle;

• loss of appetite;

• headache; 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.

Sodium phenylbutyrate dosing information

Usual Adult Dose for Urea Cycle Disorders:

Powder and Tablet:
Less than 20 kg: 450 to 600 mg/kg/day
20 kg or Greater: 9.9 to 13 g/m2/day

Comments: Administer orally in equally divided doses with each meal or feeding (i.e., 3 to 6 times a day).

Uses:
-Adjunctive therapy in the chronic management of urea cycle disorders involving deficiencies of carbamylphosphate synthetase (CPS), ornithine transcarbamylase (OTC), or argininosuccinic acid synthetase (AS).
-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:

Powder:
Less than 20 kg: 450 to 600 mg/kg/day
20 kg or Greater: 9.9 to 13 g/m2/day

Tablet:
20 kg or Less: Not recommended.
Greater than 20 kg: 9.9 to 13 g/m2/day

Comments: Administer orally in equally divided doses with each meal or feeding (i.e., 3 to 6 times a day).

Uses:
-Adjunctive therapy in the chronic management of urea cycle disorders involving deficiencies of carbamylphosphate synthetase (CPS), ornithine transcarbamylase (OTC), or argininosuccinic acid synthetase (AS).
-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.

What other drugs will affect sodium phenylbutyrate?

Tell your doctor about all medicines you use, and those you start or stop using during your treatment with sodium phenylbutyrate, especially:

• divalproex (Depakote);

• haloperidol (Haldol); or

• valproic acid (Depakene, Stavzor).

This list is not complete. Other drugs may interact with sodium phenylbutyrate, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.