Sensitive Visible Spectrophotometric Methods Development for Estimation of Sapropterin Dihydrochloride in Tablet Dosage Form

The drug Sapropterin (SAP) dihydrochloride is an enzyme cofactor and oral form of a synthetic preparation of the dihydrochloride salt of naturally occurring tetrahydrobiopterin(BH₄) and used to reduce blood phenylalanine (Phe) levels in patients with hyperphenylalaninemia (HPA). Purpose: The aim of the present investigation was to see the simple and sensitive visible spectrophotometric methods for the determination of the sapropterin dihydrochloride in bulk and tablet dosage forms. Methods: Two simple, sensitive and cost effective visible spectrophotometric methods (M₁-M₂) were developed for the estimation of sapropterin dihydrochloride in bulk and dosage forms. The first method (M₁) is based on the formation of blue reduced product by treating drug with Folin Ciocalteu (FC) reagent in the presence of sodium carbonate solution with an absorption maximum of 770nm. The second method (M₂) is based on the reaction of drug with ferric chloride and potassium ferricyanide to form a dark green colored species having absorption maxima at 704nm. Results: Beer's law obeyed in the concentration range of 2-6 μg/ml and 2.5-12.5 μg/ml for method M₁ and M₂ respectively. No interference was observed from the usually existing additives in pharmaceutical formulations and the applicability of the methods was examined by analyzing kuvan tablets containing SAP. Conclusion: The reported methods HPLC for its assay involve sophisticated equipment, which are very costly and pose problems of maintenance. To overcome these problems, the use of visible spectrophotometric technique is justifiable. The statistical data proved the accuracy, reproducibility and the precision of the proposed methods.