Sapropterin Dihydrochloride

Trade Names:
Kuvan
- Tablets 100 mg

Pharmacology

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Sapropterin is a synthetic form of tetrahydrobiopterin (BH4). Treatment with BH4 activates the residual phenylalanine hydroxylase enzyme, improves the normal oxidative metabolism of phenylalanine, and decreases phenylalanine levels in some patients.

Pharmacokinetics

Elimination

The half-life in phenylketonuric (PKU) patients is approximately 6.7 h.

Onset

In PKU patients responsive to BH4, blood phenylalanine levels decrease within 24 h after a single dose; however, max effects on phenylalanine levels may take up to 1 mo.

Special Populations

Population pharmacokinetics did not differ in patients between 9 and 49 yr of age.

Indications and Usage

In conjunction with a phenylalanine-restricted diet, sapropterin reduces blood phenylalanine levels in patients with hyperphenylalaninemia due to BH4-responsive PKU.

Contraindications

Standard considerations.

Dosage and Administration

PO Start with 10 mg/kg/day. If blood phenylalanine does not decrease from baseline, dose may be increased to 20 mg/kg/day after 1 month. Once responsiveness has been established, dose may be adjusted within range of 5 to 20 mg/kg/day. Discontinue treatment in patients whose blood phenylalanine does not decrease after 1 mo of treatment with 20 mg/kg/day. Doses above 20 mg/kg/day have not been evaluated.

General Advice

• Administer with food to increase absorption.
• Dissolve tablets in 120 to 240 mL of water or apple juice and take within 15 min of dissolution.
• May stir or crush tablets to increase speed of dissolution. Small pieces that do not dissolve or that float on the surface of the water or apple juice are safe to swallow.
• Take a missed dose as soon as possible, but do not take 2 doses on the same day.

Storage/Stability

Store at 59° to 86°F. Protect from moisture.

Drug Interactions

Additive effects may induce vasorelaxation, resulting in decreased BP.

Use with caution because the enzyme dihydropteridine reductase may be inhibited, resulting in decreased BH4 levels.

Risk of adverse reactions, including convulsions, exacerbation of convulsions, irritability, or over-stimulation, may be increased.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

MI.

CNS

Headache (15%); agitation, convulsions, dizziness, exacerbation of convulsions, irritability, overstimulation.

EENT

Rhinorrhea (11%); pharyngolaryngeal pain (10%); nasal congestion (4%).

GI

Diarrhea, vomiting (8%); GI bleeding.

Genitourinary

Polyuria.

Lab Tests

Increased gamma-glutamyltransferase (postmarketing).

Musculoskeletal

Arthralgia.

Respiratory

Cough (7%); respiratory failure, upper respiratory tract infection.

Miscellaneous

Contusion (5%); peripheral edema, post-procedural bleeding.

Precautions

Pregnancy

Category C .

Lactation

Undetermined.

Children

Safety and efficacy not established in children younger than 4 yr of age.

Elderly

Studies did not include patients older than 65 yr of age.

Renal Function

Carefully monitor use in patients with renal function impairment; use in these patients has not been evaluated.

Hepatic Function

Use with caution and close monitoring in patients with hepatic function impairment; treatment in these patients has not been evaluated.

Treatment response

Response to treatment can only be determined by a therapeutic trial.

Overdosage

Symptoms

Dizziness, headache.

Patient Information

• Advise patients not to make any dietary changes to their phenylalanine intake without consulting health care provider.
• Advise patients to inform health care provider if they have a fever or become sick because blood phenylalanine levels may increase and treatment may need to be adjusted.

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