Special Issue "Pharmaceutical Salts and Co-Crystals"

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A special issue of Pharmaceutics (ISSN 1999-4923).

Deadline for manuscript submissions: closed (30 June 2011)

Special Issue Editors

Guest Editor
Prof. Dr. Stephen R. Byrn

Department of Industrial and Physical Pharmacy, School of Pharmacy and Pharmaceutical Sciences, Purdue University, 575 Stadium Mall Drive, West Lafayette, IN 47906, USA
Website | E-Mail
Phone: 765-714-2808
Interests: solid state chemistry of drugs; stability; polymorphism; formulation; liquid crystals; cocrystals; amorphous materials; nanoparticles
Guest Editor
Dr. Daniel T. Smith

Department of Industrial and Physical Pharmacy, Purdue University, West Lafayette, IN 47906, USA
E-Mail

Keywords

  • salts
  • cocrystals
  • solubility
  • bioavailability
  • reformulation
  • formulation
  • stability
  • properties
  • flow
  • hygroscopicity
  • milling
  • physical transformations
  • crystallization
  • formation
  • disproportionation
  • X-ray
  • crystallography
  • synthesis
  • preparation
  • isolation
  • screening
  • particle size
  • morphology
  • analysis

Published Papers (4 papers)

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Research

Open AccessArticle Investigation of the Formation Process of Two Piracetam Cocrystals during Grinding
Pharmaceutics 2011, 3(4), 706-722; doi:10.3390/pharmaceutics3040706
Received: 1 July 2011 / Revised: 19 September 2011 / Accepted: 8 October 2011 / Published: 12 October 2011
Cited by 17 | PDF Full-text (3069 KB) | HTML Full-text | XML Full-text
Abstract
Cocrystal formation rates during dry grinding and liquid-assisted grinding were investigated by X-ray powder diffractometry and Raman spectroscopy. Two polymorphic forms of piracetam were used to prepare known piracetam cocrystals as model substances, i.e.,piracetam-citric acid and piracetam-tartaric acid cocrystals. Raman spectroscopy in
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Cocrystal formation rates during dry grinding and liquid-assisted grinding were investigated by X-ray powder diffractometry and Raman spectroscopy. Two polymorphic forms of piracetam were used to prepare known piracetam cocrystals as model substances, i.e.,piracetam-citric acid and piracetam-tartaric acid cocrystals. Raman spectroscopy in combination with principal component analysis was used to visualize the cocrystal formation pathways. During dry grinding, cocrystal formation appeared to progress via an amorphous intermediate stage, which was more evident for the piracetam-citric acid than for the piracetam-tartaric acid cocrystal. It was shown that liquid-assisted grinding led to faster cocrystal formation than dry grinding, which may be explained by the higher transformation rate due to the presence of liquid. The cocrystal formation rate did not depend on the applied polymorphic form of the piracetam and no polymorphic cocrystals were obtained. Full article
(This article belongs to the Special Issue Pharmaceutical Salts and Co-Crystals)
Open AccessArticle Application of Twin Screw Extrusion in the Manufacture of Cocrystals, Part I: Four Case Studies
Pharmaceutics 2011, 3(3), 582-600; doi:10.3390/pharmaceutics3030582
Received: 1 July 2011 / Revised: 17 August 2011 / Accepted: 24 August 2011 / Published: 31 August 2011
Cited by 20 | PDF Full-text (1566 KB) | HTML Full-text | XML Full-text
Abstract
The application of twin screw extrusion (TSE) as a scalable and green process for the manufacture of cocrystals was investigated. Four model cocrystal forming systems, Caffeine-Oxalic acid, Nicotinamide-trans cinnamic acid, Carbamazepine-Saccharin, and Theophylline-Citric acid, were selected for the study. The parameters of the
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The application of twin screw extrusion (TSE) as a scalable and green process for the manufacture of cocrystals was investigated. Four model cocrystal forming systems, Caffeine-Oxalic acid, Nicotinamide-trans cinnamic acid, Carbamazepine-Saccharin, and Theophylline-Citric acid, were selected for the study. The parameters of the extrusion process that influenced cocrystal formation were examined. TSE was found to be an effective method to make cocrystals for all four systems studied. It was demonstrated that temperature and extent of mixing in the extruder were the primary process parameters that influenced extent of conversion to the cocrystal in neat TSE experiments. In addition to neat extrusion, liquid-assisted TSE was also demonstrated for the first time as a viable process for making cocrystals. Notably, the use of catalytic amount of benign solvents led to a lowering of processing temperatures required to form the cocrystal in the extruder. TSE should be considered as an efficient, scalable, and environmentally friendly process for the manufacture of cocrystals with little to no solvent requirements. Full article
(This article belongs to the Special Issue Pharmaceutical Salts and Co-Crystals)
Open AccessArticle Co-Crystal Screening of Diclofenac
Pharmaceutics 2011, 3(3), 601-614; doi:10.3390/pharmaceutics3030601
Received: 28 June 2011 / Revised: 17 August 2011 / Accepted: 23 August 2011 / Published: 31 August 2011
Cited by 17 | PDF Full-text (477 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In the pharmaceutical industry, co-crystals are becoming increasingly valuable as crystalline solids that can offer altered/improved physical properties of an active pharmaceutical ingredient (API) without changing its chemical identity or biological activity. In order to identify new solid forms of diclofenac—an analgesic with
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In the pharmaceutical industry, co-crystals are becoming increasingly valuable as crystalline solids that can offer altered/improved physical properties of an active pharmaceutical ingredient (API) without changing its chemical identity or biological activity. In order to identify new solid forms of diclofenac—an analgesic with extremely poor aqueous solubility for which few co-crystal structures have been determined—a range of pyrazoles, pyridines, and pyrimidines were screened for co-crystal formation using solvent assisted grinding and infrared spectroscopy with an overall success rate of 50%. The crystal structures of three new diclofenac co-crystals are reported herein: (diclofenac)∙(2-aminopyrimidine), (diclofenac)∙(2-amino-4,6-dimethylpyrimidine), and (diclofenac)∙(2-amino-4-chloro-6-methylpyrimidine). Full article
(This article belongs to the Special Issue Pharmaceutical Salts and Co-Crystals)
Figures

Open AccessArticle Investigation of the Atypical Glass Transition and Recrystallization Behavior of Amorphous Prazosin Salts
Pharmaceutics 2011, 3(3), 525-537; doi:10.3390/pharmaceutics3030525
Received: 25 May 2011 / Revised: 27 July 2011 / Accepted: 24 August 2011 / Published: 25 August 2011
Cited by 5 | PDF Full-text (206 KB) | HTML Full-text | XML Full-text
Abstract
This manuscript studied the effect of counterion on the glass transition and recrystallization behavior of amorphous salts of prazosin. Three amorphous salts of prazosin, namely, prazosin hydrochloride, prazosin mesylate and prazosin tosylate were prepared by spray drying, and characterized by optical-polarized microscopy, differential
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This manuscript studied the effect of counterion on the glass transition and recrystallization behavior of amorphous salts of prazosin. Three amorphous salts of prazosin, namely, prazosin hydrochloride, prazosin mesylate and prazosin tosylate were prepared by spray drying, and characterized by optical-polarized microscopy, differential scanning calorimetry and powder X-ray diffraction. Modulated differential scanning calorimetry was used to determine the glass transition and recrystallization temperature of amorphous salts. Glass transition of amorphous salts followed the order: prazosin mesylate > prazosin tosylate ~ prazosin hydrochloride. Amorphous prazosin mesylate and prazosin tosylate showed glass transition, followed by recrystallization. In contrast, amorphous prazosin hydrochloride showed glass transition and recrystallization simultaneously. Density Functional Theory, however, suggested the expected order of glass transition as prazosin hydrochloride > prazosin mesylate > prazosin tosylate. The counterintuitive observation of amorphous prazosin hydrochloride having lower glass transition was explained in terms of its lower activation energy (206.1 kJ/mol) for molecular mobility at Tg, compared to that for amorphous prazosin mesylate (448.5 kJ/mol) and prazosin tosylate (490.7 kJ/mol), and was further correlated to a difference in hydrogen bonding strength of the amorphous and the corresponding recrystallized salts. This study has implications in selection of an optimal amorphous salt form for pharmaceutical development. Full article
(This article belongs to the Special Issue Pharmaceutical Salts and Co-Crystals)

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