Preparation and characterization of gastro-retentive floating microballoons of acrycoat S-100 bearing carvedilol

Abstract

G astro-retentive dosage forms have potential for use as controlled/sustained release drug delivery systems. Multiple-unit systems avoid the "all-or-none" gastric emptying nature of single-unit system. The present study was to formulate and develop a gastroretentive release delivery system for carvedilol as model drug using Acrycoat S 100 as a polymer. Carvedilol is widely used for the therapeutic management of hypertension, congestive heart failure, but it has several drawbacks such as short biological half-life of about (4-7 h) and a low oral bioavailability of 25-30%. Microballoons were prepared by o/w emulsion solvent evaporation method, organic phase consist of ethanol: Dichloromethane (1:1 v/v, 10 ml) and polyvinyl alcohol (0.75% w/v, 200 ml) as aqueous phase. The effect of various formulation and process variables were studied on surface morphology, floating behavior, drug entrapment efficiency, micromeritic properties, in vitro drug release. The designed system due to its excellent floating ability and sustained drug release could possibly be advantageous for increased bioavailability and reduced dosing frequency.

6-Aminouracil: Geometries and spectra in the isolated state and in the solid state simulation. A comparison with 5-aminouracil

“…In the isolated state the IR and Raman intensities of both d(N1eH) and d(N3eH) bands appear similar, but in the tetramer form that of d(N3eH) is slightly higher than that of d(N1eH), in accordance to that found experimentally in the IR and Raman spectra. Thus, the experimental IR band observed with weak intensity at 1456 cm À1 in KBr pellet was related to d(N3eH) mode, in agreement to its scaled frequency in the tetramer form at 1452 cm À1 , whereas we have not detected and assigned a band to d(N3eH) mode, in accordance to its null IR intensity predicted, although other authors have observed bands at 1310 [25] and 1334 [27] cm À1 , that we have reassigned to this mode. The Raman intensity of the d(N3eH) mode is larger than that of the d(N1eH) mode, in agreement with the Raman band with weak intensity detected at 1414 cm À1 and assigned as d(N3eH), and to the very weak band at 1280 cm À1 related to d(N1eH).…”

“…This assignment finds further support from that reported experimentally in 5-aminoU at 418 cm À1 (IR) and 418.9 cm À1 (Raman) [62], in 5-chlorouracil at 446 cm À1 (IR) and 457 cm À1 (R) [66], in 6-chlorouracil at 451 cm À1 (IR) and 443 cm À1 (R) [12], and in 5-fluorouracil at 419 cm À1 (IR) and 413 cm À1 (R) [65]. The experimental bands reported at 430 [25], 416 [26] and 450, 430 [27] cm À1 were reassigned to this inplane bending mode, instead of its assignment by these authors and 734 (Raman) cm À1 , and it was related to the experimental band at 764 cm À1 in IR and 768 cm À1 in Raman. This assignment finds also support with that reported experimentally in uracil molecule at 769 cm À1 [51], in 5-chlorouracil at 743 (IR) and 740 cm À1 (Raman) [66], in 6-chlorouracil at 758 (IR) and 723.3 cm À1 (Raman) [58], and in 5-fluorouracil at 740 cm À1 (IR) [67].…”

“…The experimental IR bands reported at 1721 [25], 1716 [26] and 1690 cm À1 [27] are tentatively reassigned by us to this mode. In 5-aminoU it was assigned to the band at 1675 cm À1 [62], in 6-chlorouracil at 1676 cm À1 [12] and in 5-fluorouracil at 1670 cm À1 [65].…”

“…Consequently we have reassigned these experimental bands in 6-aminoU. In Raman this mode has been assigned [27] to the band found experimentally at 1800 cm À1 . However, in the present study, we have not detected any band around 1800 cm À1 , and thus the observed band at 1701 cm À1 was related to this mode.…”

“…We have performed vibrational analysis of several derivatives of nucleic acid bases and successfully accounted for compensating discrepancies between calculated and experimental results using scaling procedures [22e24]. The IR spectrum of 6-aminoU has been studied by Aruna and Shanmugam [25], and both the IR and Raman spectra by Bayrak [26] and by Jain et al without any theoretical support [27].…”