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Sepiapterin

Generic name: sepiapterin [ SE-pi-AP-ter-in ]
Brand name: Sephience
Dosage form: oral powder for reconstitution (1000 mg; 250 mg)
Drug class: Miscellaneous metabolic agents

Medically reviewed by Drugs.com on Sep 16, 2025. Written by Cerner Multum.

What is sepiapterin?

Sepiapterin is used with diet to lower blood levels of phenylalanine in adults and children at least one month old with a certain type of phenylketonuria (PKU).

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

Sepiapterin 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.

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

Common side effects of sepiapterin may include:

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.

Warnings

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

Before taking this medicine

Tell your doctor if you have or have ever had:

It is not known if sepiapterin will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

Ask a doctor if it is safe to breastfeed while using sepiapterin.

How should I take sepiapterin?

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.

Sepiapterin can cause phenylalanine levels to get too low in people who use this medicine.

Sepiapterin is usually taken once per day with food. Be sure to eat more food after your dose.

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

Read and carefully follow the Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you don't understand these instructions.

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.

Your doctor will need to check your progress on a regular basis. Your blood will need to be tested before and during your treatment with sepiapterin.

You may have increased bleeding while taking sepiapterin. Tell your doctor if you notice any unusual bleeding, bruising, or if your bleeding continues or is very heavy.

Store unopened packets at room temperature away from moisture and heat.

Sepiapterin dosing information

Usual Adult Dose for Hyperphenylalaninemia:

Starting dosage: 60 mg/kg orally once a day
Maximum dose: 60 mg/kg/day

Evaluation Period:
-Discontinuation for lack of biochemical response:
---Discontinue this drug in patients whose blood phenylalanine (Phe) does not decrease after 2 weeks of therapy at the maximum dosage of 60 mg/kg/day.

Use: In conjunction with a Phe-restricted diet, for the treatment of hyperphenylalaninemia (HPA) in patients with sepiapterin-responsive phenylketonuria (PKU)

Usual Pediatric Dose for Hyperphenylalaninemia:

Starting dosage:
-Age less than 6 months: 7.5 mg/kg orally once a day
-Age 6 months to less than 1 year: 15 mg/kg orally once a day
-Age 1 to less than 2 years: 30 mg/kg orally once a day
-Age 2 years and older: 60 mg/kg orally once a day
Maximum dose: 60 mg/kg/day

Evaluation Period:
-Dosage titration in patients less than 2 years of age:
---After initiating therapy at the starting dosage by age, blood Phe levels should be checked within 2 weeks to verify response to therapy.
---If blood Phe does not decrease, this drug may be titrated incrementally based on blood Phe levels to a maximum of 60 mg/kg/day.
---Existing dietary protein and Phe intake should not be modified during the evaluation period.
-Discontinuation for lack of biochemical response:
---Discontinue this drug in patients whose blood Phe does not decrease after 2 weeks of therapy at the maximum dosage of 60 mg/kg/day.

Comments:
-For calculated doses less than 1000 mg/day, the final concentration of the prepared liquid mixture is 25 mg/mL.

Use: In conjunction with a Phe-restricted diet, for the treatment of HPA in patients with sepiapterin-responsive PKU

What happens if I miss a dose?

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.

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 sepiapterin?

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

What other drugs will affect sepiapterin?

Tell your doctor about all your other medicines, especially:

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

Does Sepiapterin interact with my other drugs?

Enter medications to view a detailed interaction report using our Drug Interaction Checker.

More about sepiapterin

Patient resources

Other brands

Sephience

Professional resources

Other brands

Sephience

Related treatment guides

Further information

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.