KUVAN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for KUVAN (KUVAN).

How it works

Sapropterin is a synthetic form of tetrahydrobiopterin (BH4), a cofactor for phenylalanine hydroxylase (PAH). It enhances the activity of residual PAH, thereby reducing phenylalanine levels in patients with phenylketonuria (PKU) who have BH4-responsive PAH deficiency.

What the body does with it

Metabolism	Metabolized primarily by glucuronidation via UGT1A1 and UGT1A6, with minor involvement of CYP2C19 and CYP2D6. The major metabolite is sapropterin glucuronide.
Excretion	Primarily renal excretion as unchanged drug (approximately 80-90% of the absorbed dose), with minor amounts as metabolites. Fecal excretion accounts for less than 5%.
Half-life	Terminal elimination half-life is approximately 4-6 hours in adults; in pediatric patients (4-12 years), it is about 3-4 hours. Clinical context: Twice-daily dosing maintains therapeutic concentrations.
Protein binding	Approximately 96-99% bound to plasma proteins, primarily albumin.
Volume of Distribution	Apparent volume of distribution is 1.0-1.5 L/kg, indicating extensive tissue distribution including central nervous system.
Bioavailability	Oral bioavailability is approximately 80-100% after a single oral dose; food does not significantly affect absorption.
Onset of Action	Oral administration: Clinical reduction in blood phenylalanine levels begins within 24-48 hours, with maximum effect within 2-4 weeks.
Duration of Action	Duration of action supports twice-daily dosing; blood phenylalanine levels return to baseline within 24-48 hours after discontinuation. Long-term therapy is required for sustained effect.

Classification & Brands

Dosing & administration

Adults and children 7 years and older: 20 mg/kg orally once daily, dissolved in water or apple juice. Maximum dose: 20 mg/kg/day.

Dosage form	POWDER
Renal impairment	Contraindicated in patients with estimated GFR < 30 mL/min/1.73 m². For GFR 30-59 mL/min/1.73 m²: reduce dose to 10 mg/kg once daily. Monitor serum phenylalanine levels weekly.
Liver impairment	No specific dose adjustment for hepatic impairment. Use caution in severe hepatic impairment due to limited data.
Pediatric use	Children below 7 years: 20 mg/kg orally once daily (maximum 20 mg/kg/day). For infants (0-2 years): 10 mg/kg once daily initially; titrate to 20 mg/kg based on response. Dissolve in water or apple juice; administer within 15 minutes of mixing.
Geriatric use	No specific geriatric dose adjustment. Use with caution due to age-related renal impairment; assess GFR and adjust per renal guidelines. Monitor phenylalanine levels and renal function regularly.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for KUVAN (KUVAN).

Breastfeeding	No human data on excretion in breast milk. M/P ratio unknown. Consider risk/benefit; caution advised.
Teratogenic Risk	Kuvan (sapropterin) is classified as Pregnancy Category C. Animal studies have shown fetal toxicity at high doses, but no adequate human studies exist. First trimester: theoretical risk of teratogenicity based on mechanism (BH4 cofactor). Second and third trimesters: limited data, may be used if benefit outweighs risk. Fetal monitoring recommended.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

None (no FDA boxed warning).

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to sapropterin or any component of the formulation"]

Clinical Precautions

Precautions

["Monitor blood phenylalanine levels regularly, especially during dose adjustment","Risk of hypersensitivity reactions including anaphylaxis; discontinue if severe allergic reaction occurs","Potential for gastrointestinal adverse effects (e.g., diarrhea, abdominal pain)","Avoid use in patients with known hypersensitivity to sapropterin or any excipients","May cause headache, rhinorrhea, or pharyngolaryngeal pain"]

Clinical Tips & Counseling

Drug interactions

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KUVAN

Clinical safety rating: caution

Comprehensive clinical and safety monograph for KUVAN (KUVAN).

How it works

What the body does with it

Metabolism	Metabolized primarily by glucuronidation via UGT1A1 and UGT1A6, with minor involvement of CYP2C19 and CYP2D6. The major metabolite is sapropterin glucuronide.
Excretion	Primarily renal excretion as unchanged drug (approximately 80-90% of the absorbed dose), with minor amounts as metabolites. Fecal excretion accounts for less than 5%.
Half-life	Terminal elimination half-life is approximately 4-6 hours in adults; in pediatric patients (4-12 years), it is about 3-4 hours. Clinical context: Twice-daily dosing maintains therapeutic concentrations.
Protein binding	Approximately 96-99% bound to plasma proteins, primarily albumin.
Volume of Distribution	Apparent volume of distribution is 1.0-1.5 L/kg, indicating extensive tissue distribution including central nervous system.
Bioavailability	Oral bioavailability is approximately 80-100% after a single oral dose; food does not significantly affect absorption.
Onset of Action	Oral administration: Clinical reduction in blood phenylalanine levels begins within 24-48 hours, with maximum effect within 2-4 weeks.
Duration of Action	Duration of action supports twice-daily dosing; blood phenylalanine levels return to baseline within 24-48 hours after discontinuation. Long-term therapy is required for sustained effect.

Classification & Brands

Dosing & administration

Adults and children 7 years and older: 20 mg/kg orally once daily, dissolved in water or apple juice. Maximum dose: 20 mg/kg/day.

Dosage form	POWDER
Renal impairment	Contraindicated in patients with estimated GFR < 30 mL/min/1.73 m². For GFR 30-59 mL/min/1.73 m²: reduce dose to 10 mg/kg once daily. Monitor serum phenylalanine levels weekly.
Liver impairment	No specific dose adjustment for hepatic impairment. Use caution in severe hepatic impairment due to limited data.
Pediatric use	Children below 7 years: 20 mg/kg orally once daily (maximum 20 mg/kg/day). For infants (0-2 years): 10 mg/kg once daily initially; titrate to 20 mg/kg based on response. Dissolve in water or apple juice; administer within 15 minutes of mixing.
Geriatric use	No specific geriatric dose adjustment. Use with caution due to age-related renal impairment; assess GFR and adjust per renal guidelines. Monitor phenylalanine levels and renal function regularly.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for KUVAN (KUVAN).

Breastfeeding	No human data on excretion in breast milk. M/P ratio unknown. Consider risk/benefit; caution advised.
Teratogenic Risk	Kuvan (sapropterin) is classified as Pregnancy Category C. Animal studies have shown fetal toxicity at high doses, but no adequate human studies exist. First trimester: theoretical risk of teratogenicity based on mechanism (BH4 cofactor). Second and third trimesters: limited data, may be used if benefit outweighs risk. Fetal monitoring recommended.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

None (no FDA boxed warning).

Side Effect Profile

Serious Effects

Absolute Contraindications

["Hypersensitivity to sapropterin or any component of the formulation"]

Clinical Precautions

Precautions

Clinical Tips & Counseling

Drug interactions

Loading safety data…