Article

Improvement of physicomechanical properties of carbamazepine by recrystallization at different pH values.

Faculty of Pharmacy and Drug, Applied Research Centre, Tabriz University of Medical Sciences, Tabriz 51664, Iran.
Acta Pharmaceutica (Impact Factor: 1.16). 07/2009; 59(2):187-97. DOI: 10.2478/v10007-009-0015-x
Source: PubMed

ABSTRACT The morphology of crystals has an appreciable impact role on the physicochemical properties of drugs. Drug properties such as flowability, dissolution, hardness and bioavailability may be affected by crystallinity behaviours of drugs. The objective of this study was to achieve an improved physicomechanical property of carbamazepine powder through recrystallization from aqueous solutions at different pH values. For this purpose, carbamazapine was recrystallized from aqueous solutions at different pH values (1, 7, 11). The morphology of crystals was investigated using scanning electron microscopy; X-ray powder diffraction (XRPD) was used to identify polymorphism; thermodynamic properties were analyzed using differential scanning calorimetery (DSC). Dissolution rate was determined using USP dissolution apparatus. Mechanical behavior of recrystallized carbamazepine powders was investigated by making tablets under different compaction pressure and measuring their hardness. SEM studies showed that the carbamazepine crystallization in different media affected the morphology and size of carbamazepine crystals. The shape of carbamazepine crystals changed from flaky or thin plate-like to needle shape. XRPD and DSC results ruled out any crystallinity changes occurring due to the temperature during recrystallization procedure or pH of crystallization media. The crushing strength of tablets indicated that all of the recrystallized carbamazepine samples had better compactiblity than the original carbamazepine powder. In vitro dissolution studies of carbamazepine samples showed a higher dissolution rate for carbamazepine crystals obtained from media with pH 11 and 1. Carbamazepine particles recrystallized from aqueous solutions of different pH values (all media) appeared to have superior mechanical properties to those of the original carbamazepine sample.

0 Bookmarks
 · 
211 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this paper, an electrospray technique followed by annealing at high temperatures was developed to produce nanocrystals of carbamazepine (CBZ), a poorly water-soluble drug, for continuous pharmaceutical manufacturing process. Electrospraying solutions of CBZ in methanol obeys the expected scaling law of current, which is I ∼ Q(1/2) (I, electrical current; Q, flow rate), for liquids with sufficiently high conductivity and viscosity. Lower flow rates during electrospraying were preferred to produce smaller diameters of monodisperse, dense CBZ nanoparticles. CBZ nanoparticles were predominantly amorphous immediately after electrospraying. Crystallization of CBZ nanoparticles was accelerated by annealing at high temperatures. CBZ nanocrystals with the most stable polymorph, form III, were obtained by annealing at 90°C, which is above the transition temperature, 78°C, for the enantiotropic CBZ form III and form I. The solubility and dissolution rates of CBZ nanocrystals increased significantly as compared with those of CBZ bulk particles. Therefore, electrospray technology has the potential to produce pharmaceutical dosage forms with enhanced bioavailability and can readily be integrated in a continuous pharmaceutical manufacturing process.
    Journal of Pharmaceutical Sciences 12/2011; 101(3):1178-88. · 3.13 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Decay rate estimation has been proposed as an effective method for landmine and unexploded ordnance (UXO) detection. The physical basis for this strategy is that every object in the target library possesses a unique set of decay rates. In theory, the characteristic decay rates can be estimated from the measured electromagnetic induction (EMI) response, and then utilized for target detection and subsequent identification. Unfortunately, decay rate estimation is notoriously difficult and this difficulty adversely impacts target identification performance. Since the basis for this approach to target detection and identification is that targets are uniquely characterized by their decay rates, discrimination performance is dependent upon decay rate estimation performance. The Cramer-Rao lower bound (CRLB) for decay rate and amplitude coefficient estimates is utilized to investigate the fundamental limitations on target identification via decay rate estimation. It is shown how both the temporal sampling strategy and the number of poles being estimated affects pole estimation and target identification performance
    Geoscience and Remote Sensing Symposium, 2000. Proceedings. IGARSS 2000. IEEE 2000 International; 02/2000
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study describes the evaluation and optimization of a crystallizing process capable of efficiently purifying vancomycin in high purity and yield. In particular, we observed how the main process parameters influenced the formation of crystals, determined their morphology, and monitored purity and yield. Acetone was shown to be more effective than alcohol solvents for the crystallization of vancomycin. The optimal distilled water/acetone ratio, storage temperature, storage time, pH, conductivity, initial vancomycin concentration and stirrer velocity were shown to be 1: 3.5 (v/v), 10 °C, 24 h, pH 2.5, 20 ms/cm, 0.1 g/mL, and 640 rpm, respectively. Temperature had a decisive influence on crystal formation; crystals were successfully produced at 10 °C, while at other temperatures, conglomeration, disintegration and cohesion occurred. Crystal growth developed over time and was complete at about 24 h. Vancomycin purity remained at about 97.0% irrespective of storage time while the yield increased over time, reaching a maximum of 95.0% at around 24 h, after which there was no substantial change. Crystallization occurred over a certain range of pH (2.5–3.0), but purity and yield were highest at pH 2.5. When the pH was outside this range, a conglomeration (gelation) phenomenon prevented the efficient production of crystals. Vancomycin crystals were produced irrespective of the stirrer velocity, which had no influence on purity; however, the highest yield of vancomycin was obtained at 640 rpm. Key wordsVancomycin-Crystallization-Purification-Optimization of Process Parameters-Identification of Morphology
    Korean Journal of Chemical Engineering 01/2010; 27(5):1538-1546. · 1.06 Impact Factor

Full-text (2 Sources)

Download
70 Downloads
Available from
May 23, 2014