Sapropterin


Generic Medicine Info
Indications and Dosage
Oral
Hyperphenylalaninaemia due to phenylketonuria
Adult: As sapropterin dihydrochloride: Initially, 10 mg/kg once daily, preferably in the morning, adjusted according to desired phenylalanine levels. Usual maintenance dose: 5-20 mg/kg once daily.
Child: ≥4 years Same as adult dose.

Oral
Hyperphenylalaninaemia due to tetrahydrobiopterin (BH4) deficiency
Adult: As sapropterin dihydrochloride: Initially, 2-5 mg/kg once daily, preferably in the morning, adjusted according to desired phenylalanine levels. Max total dose: 20 mg/kg daily, may alternatively be given in 2-3 divided doses.
Child: ≥4 years Same as adult dose.
Reconstitution
Dissolve with 120-240 mL of water or apple juice.
Special Precautions
Patient with history of convulsions. Hepatic and renal impairment. Children. Pregnancy and lactation.
Adverse Reactions
Significant: Gastritis, hyperactivity, hypersensitivity reactions, hypophenylalaninaemia.
Gastrointestinal disorders: Diarrhoea, vomiting, abdominal pain, dyspepsia, nausea.
Nervous system disorders: Headache.
Respiratory, thoracic and mediastinal disorders: Upper respiratory tract infection, rhinorrhoea, cough, nasal congestion, pharyngolaryngeal pain.
Monitoring Parameters
Monitor serum phenylalanine and tyrosine levels at baseline, 1 week after treatment, then periodically and regularly thereafter; blood pressure, nutrient intake, psycho-motor development, signs and symptoms of gastritis, hyperactivity.
Overdosage
Symptoms: Headache and dizziness. Management: Symptomatic treatment.
Drug Interactions
Increased excitability, irritability and exacerbation of convulsion with levodopa. May increase the vasodilating effect of phosphodiesterase type-5 (PDE-5) inhibitors, glyceryl trinitrate, isosorbide dinitrate (ISDN). Decreased serum concentration with methotrexate, trimethoprim.
Food Interaction
Increased absorption with food.
Action
Description: Sapropterin is a synthetic form of tetrahydrobiopterin (BH4), an endogenous cofactor for phenylalanine hydroxylase (PAH). PAH enzyme hydroxylates phenylalanine through an oxidative reaction to form tyrosine; PAH activity is absent or deficient in patients with phenylketonuria. Sapropterin enhances the activity of residual PAH hence, improves normal phenylalanine metabolism and decreases serum phenylalanine level concentration.
Onset: Within 24 hours.
Duration: 24 hours.
Pharmacokinetics:
Absorption: Increased absorption with food. Time to peak plasma concentration: 3-4 hours.
Distribution: Distributed mainly to the kidneys, adrenal glands, spleen and liver.
Metabolism: Metabolised in the liver by dihydrofolate reductase and dihydropteridine reductase to dihydrobiopterin and dihydroxanthopterin as main metabolites.
Excretion: Mainly via faeces; urine (small amount). Elimination half-life: Approx 7 hours (range: 4-17 hours).
Chemical Structure

Chemical Structure Image
Sapropterin

Source: National Center for Biotechnology Information. PubChem Database. Sapropterin, CID=135398654, https://pubchem.ncbi.nlm.nih.gov/compound/Sapropterin (accessed on Jan. 23, 2020)

Storage
Store between 20-25°C. Protect from moisture.
Any unused portions should be disposed of in accordance with local requirements.
ATC Classification
A16AX07 - sapropterin ; Belongs to the class of various alimentary tract and metabolism products.
References
Anon. Sapropterin. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 04/06/2018.

Anon. Sapropterin. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 04/06/2018.

Buckingham R (ed). Sapropterin Hydrochloride. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 04/06/2018.

Joint Formulary Committee. Sapropterin Dihydrochloride. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 04/06/2018.

Kuvan 100 mg Soluble Tablets (BioMarin International Limited). European Medicines Agency [online]. Accessed 04/06/2018.

Kuvan Tablet (BioMarin Pharmaceutical Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 04/06/2018.

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