Ammonio Methacrylate Copolymer (Type B)-Diltiazem Interactions in Solid Dispersions and Microsponge Drug-Delivery Systems

This paper presents a complex analytical study on the distribution, solubility, amorphization, and compatibility of diltiazem within the composition of Eudragit RS 100-based particles of microspongeous type. For this purpose, a methodology combining attenuated total reflectance Fourier transform infrared (ATR-FTIR) absorption spectroscopy, differential scanning calorimetry (DSC), scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDX), and in vitro dissolution study is proposed. The correct interpretation of the FTIR and drug-dissolution results was guaranteed by the implementation of two contrasting reference models: physical drug–polymer mixtures and casting-obtained, molecularly dispersed drug–polymer composites (solid dispersions). The spectral behavior of the drug–polymer composites in the carbonyl frequency (νCO) region was used as a quality marker for the degree of their interaction/mutual solubility. A spectral-pattern similarity between the microsponge particles and the solid dispersions indicated the molecular-type dispersion of the former. The comparative drug-desorption study and the qualitative observations over the DSC and SEM-EDX results confirmed the successful synthesis of a homogeneous coamorphous microsponge-type formulation with excellent drug-loading capacity and “controlled” dissolution profile. Among them, the drug-delivery particles with 25% diltiazem content (M-25) were recognized as the most promising, with the highest population of drug molecules in the polymer bulk and the most suitable desorption profile. Furthermore, an economical and effective analytical algorithm was developed for the comprehensive physicochemical characterization of complex delivery systems of this kind.

Carboxylic Acid Counterions in FDA-Approved Pharmaceutical Salts

Salification is one of the powerful and widely employed approaches to improve the biopharmaceutical properties of drugs. The FDA's eighty-year trajectory of new drug approvals depicts around one-third of the drugs clinically used as their pharmaceutical salts. Among various cationic and anionic counterions used in FDA-approved pharmaceutical salts, the carboxylic acids have significantly contributed. A total of 94 pharmaceutical salts discovered during 1943-2020 comprises carboxylic acids as counterions with a major contribution of acetate, maleate, tartrate, fumarate, and succinate. Hydrocodone tartrate is the first FDA-approved carboxylate salt approved in 1943. Overall, the analysis shows that fifteen carboxylic acid counterions are present in FDA-approved pharmaceutical salts with a major share of acetate (18 drugs). This review provides an account of FDA-approved carboxylate salts from 1939 to 2020. The decade-wise analysis indicates that 1991-2000 contributed a maximum number of carboxylate salts (24) and least (3) in 1939-1950. The technical advantage of carboxylate salts over free-base or other counterions is also discussed. Graphical Abstract.

Multicomponent ionic crystals of diltiazem with dicarboxylic acids toward understanding the structural aspects driving the drug-release

Diltiazem (DIL) is a calcium channel blocker antihypertensive drug commonly used in the treatment of cardiovascular disorders. Due to the high solubility and prompt dissolution of the commercial form hydrochloride (DIL-HCl) that is closely related to short elimination drug half-life, this API is known for exhibiting an unfitted pharmacokinetic profile. In an attempt to understand how engineered multicomponent ionic crystals of DIL with dicarboxylic acids can minimize these undesirable biopharmaceutical attributes, herein, we have focused on the development of less soluble and slower dissolving salt/cocrystal forms. By the traditional solvent evaporation method, two hydrated salts of DIL with succinic and oxalic acids (DIL-SUC-H₂O and DIL-OXA-H₂O), and one salt-cocrystal with fumaric acid (DIL-FUM-H₂FUM) were successfully prepared. An in-depth crystallographic description of these new solid forms was conducted through single and powder X-ray diffraction (SCXRD, PXRD), Hirshfeld surface (HS) analysis, energy framework (EF) calculations, Fourier Transform Infrared (FT-IR) spectroscopy, and thermal analysis (TG, DSC, and HSM). Structurally, the inclusion of dicarboxylic acids in the crystal structures provided the formation of 2D-sheet assemblies, where ionic pairs (DIL⁺/anion^-) are associated with each other via H-bonding. Consequently, a substantial lowering in both solubility (16.5-fold) and intrinsic dissolution rate (13.7-fold) of the API has been achieved compared to that of the hydrochloride salt. These findings demonstrate the enormous potential of these solid forms in preparing of novel modified-release pharmaceutical formulations of DIL.

Fabrication of an osmotic 3D printed solid dosage form for controlled release of active pharmaceutical ingredients

In pharmaceutical formulations, pharmacokinetic behavior of the Active Pharmaceutical Ingredients (API's) is significantly affected by their dissolution profiles. In this project, we attempted to create personalized dosage forms with osmotic properties that exhibit different API release patterns via Fused Deposition Modelling (FDM) 3D printing. Specifically, cellulose acetate was employed to create an external shell of an osmotically active core containing Diltiazem (DIL) as model drug. By removing parts of the shell (upper surface, linear lateral segments) were created dosage forms that modify their shape at specific time frames under the effect of the gradually induced osmotic pressure. Hot-Melt Extrusion (HME) was employed to fabricate two different 3DP feeding filaments, for the creation of either the shell or the osmotic core (dual-extrusion printing). Printed formulations and filaments were characterized by means of (TGA, XRD, DSC) and inspected using microscopy (optical and electron). The mechanical properties of the filaments were assessed by means of micro- and macro mechanical testing, whereas micro-Computed Tomography (μCT) was employed to investigate the volumetric changes occurring during the hydration process. XRD indicated the amorphization of DIL inside HME filaments and printed dosage forms, whereas the incorporated NaCl (osmogen) retained its crystallinity. Mechanical properties' testing confirmed the printability of produced filaments. Dissolution tests revealed that all formulations exhibited sustained release differing at the initiation time of the API dissolution (0, 120 and 360 min for the three different formulations). Finally, μCT uncovered the key structural changes associated with distinct phases of the release profile. The above results demonstrate the successful utilization of an FDM 3D printer in order to create osmotic 3D printed formulations exhibiting sustained and/or delayed release, that can be easily personalized containing API doses corresponding to each patient's specific needs.

Microbatch under-oil salt screening of organic cations: single-crystal growth of active pharmaceutical ingredients

Multicomponent solid forms of active pharmaceutical ingredients represent a modern method of tuning their physicochemical properties. Typically, salts are the most commonly used multicomponent solid form in the pharmaceutical industry. More than 38% are formulated as organic cations. Salt screening is an essential but demanding step when identifying the most appropriate formulation. The microbatch under-oil crystallization technique of proteins has been combined with the previously developed high-throughput vapour-diffusion screening for use as a novel method of primary salt screening of organic cations. The procedure allows the set up of about 100 crystallization experiments per 30 min. This requires between 17 and 564 mg of screened cationic active pharmaceutical ingredients, which were of moderate to very high water solublity. Five distinct organic salts, three of them diverse active pharmaceutical compounds or the other enantiomer thereof, in the form of chloride salts were tested. The screening was extremely successful; at least two new single-crystal structures could be obtained for each particular compound and many more salts as single crystals were formed compared with our previous vapour-diffusion method.

In vitro and ex vivo studies on diltiazem hydrochloride-loaded microsponges in rectal gels for chronic anal fissures treatment

Diltiazem hydrochloride, topically applied at 2% concentration, is considered effective for the treatment of chronic anal fissures, although it involves several side effects among which anal pruritus and postural hypotension. To test the hypothesis that a sustained delivery system of diltiazem hydrochloride may be helpful for the treatment of chronic anal fissures, in the present study we evaluated the potential of gels containing diltiazem hydrochloride entrapped in microsponges. Such microsponges were based on Eudragit RS 100 and the effect of some formulation variables was assessed by a 2³ full factorial screening design. An optimized formulation of diltiazem hydrochloride microsponges was dispersed in Methylcellulose 2% or Poloxamer 407 20% and the resulting gels (micro-l-diltiazem hydrochloride 2%) were subjected to in vitro drug release, ex vivo permeability and drug deposition after application on porcine rectal mucosa. The results showed a prolonged release up to 24 h from micro-l-diltiazem hydrochloride at 2% in the gels. The permeation tests revealed up to 18% higher drug retention on the mucosal tissue after 24 h by the micro-l-diltiazem hydrochloride 2% gels compared to conventional diltiazem hydrochloride gels at 2%. These results suggest that diltiazem hydrochloride-loaded microsponges dispersed in rectal gels may be useful to overcome some limitations of conventional local chronic anal fissure therapy.

Crystal structure of 3-(4-hy-droxy-phen-yl)-2-[(E)-2-phenyl-ethen-yl]quinazolin-4(3H)-one

The title compound, C22H16N2O2 {systematic name: 3-(4-hy-droxy-phen-yl)-2-[(E)-2-phenyl-ethen-yl]quinazolin-4(3H)-one}, consists of a substituted 2-[(E)-2-aryl-ethen-yl]-3-aryl-quinazolin-4(3H)-one skeleton. The substituents at the ethyl-ene fragment are located in trans positions. The phenyl ring is inclined to the quinazolone ring by 26.44 (19)°, while the 4-hy-droxy-phenyl ring is inclined to the quinazolone ring by 81.25 (8)°. The phenyl ring and the 4-hy-droxy-phenyl ring are inclined to one another by 78.28 (2)°. In the crystal, mol-ecules are connected via O-H⋯O hydrogen bonds, forming a helix along the a-axis direction. The helices are linked by C-H⋯π inter-actions, forming slabs parallel to (001).

Novel solid forms of oxaprozin: cocrystals and an extended release drug–drug salt of salbutamol

Novel solid forms of an anti-inflammatory drug, oxaprozin, were identified. A drug–drug salt of oxaprozin with salbutamol was proved promising for development of extended release tablet formulations of salbutamol.