Abstract
Objective: The objective of the present study was to improve the aqueous solubility and dissolution characteristics of the loop diuretic furosemide (FUR); a class IV drug in the Biopharmaceutical Classification System (BCS) using solid dispersion technique.
 Methods: Solvent evaporation and kneading methods were used to produce solid dispersions of FUR in different ratios with the hydrophilic carrier polyvinylpyrrolidone K-30 (PVP-K30). The prepared solid dispersions were evaluated in terms of solubility study, percentage yield, drug content and Fourier transform infrared spectroscopic study (FT-IR). Tablets containing the optimized formula of solid dispersions ( were formulated and their dissolution characteristics were compared with commercial furosemide tablets.
 Results: The prepared solid dispersions showed an increase in aqueous solubility, especially those formulated in a 1:2 drug: carrier ratio using solvent evaporation method ( it showed a four-fold increase in solubility compared to the parent drug. The absence of drug-carrier chemical interactions that could affect the dissolution was proved by FT-IR. Solid dispersion tablets exhibited a better dissolution profile in simulated gastric fluid pH 1.2 at 37°C ± 0.5 than the commercial FUR tablets in terms of mean dissolution time (8.44 min) and dissolution efficiency in 30 min (42.54%). Both FUR solid dispersions and commercial tablets followed Weibull and Krosmeyer models as the two best models of drug release kinetics proving that they were immediate release.
 Conclusion: According to the results obtained in this study, solid dispersion techniques could be successfully used for the enhancement of aqueous solubility and dissolution rate of FUR.
Highlights
Oral drug delivery, especially oral solid dosage forms such as tablets and capsules are the most desired administration route for many drugs, due to its several advantages over other formulations
Solubility study of FUR solid dispersions with polyethylene glycols (PEGs) and polyvinylpyrrolidone K-30 (PVP-K30) prepared by fusion and solvent evaporation method indicated that increasing the concentration of the carrier will enhance the aqueous solubility of the poorly soluble drug; this finding is reported by Patel et al, they found that the solubility of FUR-PVP K30 solid dispersions in a ratio of 1:10 was enhanced by 23-fold compared with poorly soluble FUR [21]
This study showed that solid dispersions of FUR with PVP-K30 in different ratios successfully enhanced the aqueous solubility and dissolution rate of FUR
Summary
Especially oral solid dosage forms such as tablets and capsules are the most desired administration route for many drugs, due to its several advantages over other formulations. It is the most commonly used route due to its greater stability, ease of administration, high patient compliance, the accuracy of doses, costeffectiveness, and flexibility of dosage form design [1]. The bioavailability and therapeutic effectiveness of a drug administered by oral route depend on several factors, including aqueous solubility, drug permeability, dissolution rate, systemic metabolism, and susceptibility to efflux mechanisms. Water-soluble drugs often require higher doses to reach therapeutic plasma concentrations after oral administration, they have slow drug absorption that leads to inadequate and variable bioavailability [2]. There are many approaches to increase the solubility of a poorly water-soluble drug and improve its bioavailability, such as grinding, use of surfactants, salt formation, pH adjustments, prodrugs, complexation with cyclodextrins, self-emulsifying formulations, micronization, emulsions and liposomes [4]
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