Evaluation of Pharmaco-Equivalence Properties of Lisinopril Dihydrate Tablets in Saudi Arabia: A Local Comparative Study

Background: Lisinopril, a widely prescribed antihypertensive medication, is available in multiple oral tablet formulations in the Saudi market.As the quality parameters of these formulations can vary between brands, assessing the critical quality attributes of lisinopril tablets is essential for ensuring therapeutic consistency.This study aimed to evaluate various quality control parameters, chemical compatibility, and pharmaceutical equivalence criteria for three different brands (A ,B, and C) and strengths (5, 10, and 20 mg) of lisinopril dihydrate (LD) tablets available in Saudi Arabia.Methods: The tablets were analyzed for compliance with United States Pharmacopeia (USP) standards, including uniformity of dosage units, hardness, friability, disintegration, and dissolution characteristics.In vitro dissolution profiles were assessed using both model-dependent and model-independent methods, comparing each brand to the reference innovator product (brand A).Results: Data indicated that all brands met USP requirements for content uniformity, disintegration, and dissolution.All tested tablets exhibited rapid disintegration, with times under 3 minutes.Although all brands demonstrated high hardness and low friability, two products (LD5 B and LD10 C) had out-ofcompliance friability values (3.61% and 1.08%, respectively).Infrared (IR) spectroscopy confirmed the absence of chemical interactions between the active ingredient and tablet excipients.Additionally, dissolution rates for all brands met USP criteria, with at least 80% drug release within 45 minutes.Kinetic analysis revealed that no single model could fully describe the drug release profiles across the tested brands.Conclusions: All lisinopril tablets assessed were compliant with USP specifications and generally met local regulatory requirements, though minor variations in tablet characteristics suggest variances in production processes across brands.