The development of potential new active substances that exhibit high pharmacological potential but are poorly water soluble has challenged pharmaceutical technology to develop new approaches that would increase their solubility and, thus, their bioavailability. Nanofibers as a delivery system that can potentially lead to supersaturation in the gastrointestinal tract are very promising. In scope of our research, we have used electrospinning to produce hydrophilic polymer nanofibers with incorporated carvedilol. In addition to the main polymers, namely poloxamer 407 and polyethylene oxide, and the active substance carvedilol, we incorporated in nanofibers also a potential precipitation inhibitor hydroxypropyl methylcellulose or Soluplus. The manufacture of nanofibers with hydroxypropyl methylcellulose required some adjustments, such as less concentrated ethanol for preparation of a polymer solution and increased distance between the needle tip and the collector. We evaluated the carvedilol release from nanofibers by the drug release test, which has shown immediate drug release from all formulations, except nanofibers with Methocel K4M. We evaluated the effectiveness of individual polymeric precipitation inhibitor to maintain the supersaturation state with the solubility test. The nanofibers with Pharmacoat 606 and Pharmacoat 615 did not significantly extend the duration of carvedilol supersaturation state compared to the nanofibers without the precipitation inhibitor. On the other hand, Soluplus incorporated in nanofibers increased the solubility of carvedilol and prolonged the duration of carvedilol supersaturation after its release from the nanofibers. This proved good solubilizing properties of Soluplus and its efficacy as precipitation inhibitor. Pre-dissolution of the polymeric precipitation inhibitors in dissolution medium did not extend the duration of the carvedilol supersaturation state, when released from nanofibers without incorporated precipitation inhibitor, except in case of pre-dissolved Soluplus in a weight ratio of 1: 1 with carvedilol. We have also revealed that nanofibers significantly increase the solubility and prolong the duration of carvedilol supersaturation compared to the polymer film, and even more when compared to the physical mixture with the same composition. This is how we proved that the dosage form is also important in addition to the formulation composition in increasing the drug solubility. However, amorphous state of carvedilol in nanofibers could not be confirmed by differential scanning calorimetry.
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