Abstract
Purpose: To develop a first-order derivative spectrophotometric method for the determination of trimethoprim (TMP) and sulfamethoxazole (SMX) from fixed-dose combination generic products using a flow-through cell technique. Methods: Absorbance measurement was achieved at 247.8 and 257.9 nm for trimethoprim and sulfamethoxazole, respectively. USP Apparatus 4 with 22.6 mm cells, laminar flow at 16 ml/min, and 0.1 N HCl at 37 °C as dissolution medium, were used. Dissolution profiles were compared with modeldependent and independent methods. Results: All the products met the pharmacopeial dissolution criterion (Q ≥ 70 %, at 60 min), except SMX in two products (SC 400 mg and SB1 800 mg) using the flow-through cell (53.62 and 49.74 % dissolved, respectively). Using both USP apparatuses, significant differences in mean dissolution time and dissolution efficiency values were found (p < 0.05). All products were in line with Weibull’s kinetics and significant differences in derived parameters (Td) values were found (p < 0.05). Conclusion: Determination of TMP and SMX by derivative spectrophotometry can easily be employed for dissolution studies using the flow-through cell technique. However, it would be necessary to determine correlation with in-vivo test results in order to assure safe interchangeability. Keywords: Trimethoprim, Sulfamethoxazole, Flow-through cell method, First-order derivative spectrophotometry, Fixed-dose combination generic drugs
Highlights
Several authors have been worried about safe interchangeability between branded products and its generic counterpart or even among different generic products
HPLC analysis for drugs quantification is recommended
The aim of this study was to apply a first-order derivative spectrophotometric method, especially developed for dissolution studies (USP paddle method), in the determination of dissolution profiles of TMP and SMX from fixed-dose combination generic drugs obtained with the flow-through cell system
Summary
Several authors have been worried about safe interchangeability between branded products and its generic counterpart or even among different generic products. For several drugs, interesting and different results have been reported [1,2]. Importance of in-vitro dissolution test to guarantee a best quality in generic medications is widely discussed by regulatory organisms [3]. According to FDA and WHO guidelines, some generic drugs can be registered on the basis of only in-vitro data (dissolution test) without testing their in-vivo performance [4]. In Mexico, as in other parts of the world, trimethoprim-sulfamethoxazol (TMP-SMX) immediate-release oral fixed-dosage forms are marketed as generic drugs. The combination is prepared in different formulations but tablets are the most commonly used, mainly for the advantages of patient management and intake of a solid dosage form
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