DEVELOPMENT OF A SPECTROPHOTOMETRIC METHOD FOR THE DETERMINATION OF SILDENAFIL CITRATE PREPARATION IN THE FORM OF SMALL-BATCH POWDERS FOR PERSONALISED THERAPY

Abstract

In the current context of personalised medicine, ensuring the quality of sildenafil citrate medicinal products manufactured in small batches is of particular relevance, especially for paediatric patients and individuals requiring individually adjusted dosing. Sildenafil citrate is recommended by international clinical guidelines for the treatment of pulmonary hypertension in children; however, medicinal products with the required doses of 5 mg and 10 mg are not available on the pharmaceutical market of Ukraine. This leads to the forced use of industrially manufactured tablets outside their authorised indications (off-label), which is associated with the risk of dosing errors and reduced pharmacotherapy safety. Therefore, the extemporaneous preparation of dose-adjusted sildenafil citrate powders represents an important tool for improving accessibility and personalisation of treatment, yet it requires the implementation of reliable, rapid, and economically feasible analytical quality control methods. Within the framework of this study, a spectrophotometric method for the determination of sildenafil citrate was developed and validated, adapted specifically to the conditions of in-pharmacy quality control. Characteristic spectral parameters of the active substance in 0.1 M hydrochloric acid solution were established: an absorption maximum at 292 nm and a minimum at 267 nm, which enable simultaneous identification and quantitative determination. Validation of the method in accordance with the requirements of the State Pharmacopoeia of Ukraine confirmed its specificity, linearity (supported by a high correlation coefficient r = 0.9993), robustness, accuracy, and precision, which indicates the reproducibility of the method and its suitability for pharmaceutical analysis. To ensure product quality throughout its shelf life, the stability of the medicinal product was evaluated using the proposed method. It was established that the investigated preparation remains stable for 180 days under storage at room temperature in the manufacturer's sealed packaging. Thus, the proposed spectrophotometric method is simple, accessible, cost-effective, and fully suitable for routine analytical control of sildenafil citrate powders prepared extemporaneously in pharmacy settings. Its implementation improves the quality and safety of personalised therapy and may serve as a basis for developing draft analytical regulatory documentation and further elaboration of a monograph for inclusion in the State Pharmacopoeia of Ukraine.