Higher Intrinsic Dissolution Rate Research Articles

Unexpected Salt/Cocrystal Polymorphism of the Ketoprofen–Lysine System: Discovery of a New Ketoprofen–l-Lysine Salt Polymorph with Different Physicochemical and Pharmacokinetic Properties

Ketoprofen–l-lysine salt (KLS) is a widely used nonsteroidal anti-inflammatory drug. Here, we studied deeply the solid-state characteristics of KLS to possibly identify new polymorphic drugs. Conducting a polymorph screening study and combining conventional techniques with solid-state nuclear magnetic resonance, we identified, for the first time, a salt/cocrystal polymorphism of the ketoprofen (KET)–lysine (LYS) system, with the cocrystal, KET–LYS polymorph 1 (P1), being representative of commercial KLS, and the salt, KET–LYS polymorph 2 (P2), being a new polymorphic form of KLS. Interestingly, in vivo pharmacokinetics showed that the salt polymorph has significantly higher absorption and, thus, different pharmacokinetics compared to commercial KLS (cocrystal), laying the basis for the development of faster-release/acting KLS formulations. Moreover, intrinsic dissolution rate (IDR) and electronic tongue analyses showed that the salt has a higher IDR, a more bitter taste, and a different sensorial kinetics compared to the cocrystal, suggesting that different coating/flavoring processes should be envisioned for the new compound. Thus, the new KLS polymorphic form with its different physicochemical and pharmacokinetic characteristics can open the way to the development of a new KET–LYS polymorph drug that can emphasize the properties of commercial KLS for the treatment of acute inflammatory and painful conditions.

Influence of high pressure compaction on solubility and intrinsic dissolution of ibuprofen binary mixtures employing standard excipients

Enabling formulations often depend on functional excipients. However, the question remains whether excipients regarded as standard establish similar interactions and subsequently improvement of solubility when employed at unusual manufacturing process conditions. In this study, compaction of API under high pressure in the presence of hydrophilic excipients is proposed as a technique to improve the solubility and/or dissolution rate with an acceptable preservation of the supersaturation state. Binary mixtures of ibuprofen (IBU) with hydroxypropyl cellulose, isomalt, mannitol and sorbitol were compacted applying high pressure (500 MPa) with and without a previous co-milling step. Intrinsic dissolution rate (IDR) was selected to characterize and evaluate dissolution performance. The IDR of neat IBU increased from 5 to 88 fold and the aqueous solubility in the range of 3 to 54%. Regarding the polyols isomalt showed the highest impact on solubility and dissolution, without changing the crystallinity of IBU independent of a co-milling step. Even higher impact was achieved in combination with HPC. However, only without a previous co-milling step, ibuprofen remained crystalline, while co-milling induced an amorphous IBU-content of 38%. Based on XRPD and DSC findings, higher IDR and solubility values correlated with crystal modifications as well as IBU/excipient interactions.

Characterization and Stability of Amorphous Tadalafil and Four Crystalline Polymorphs.

Tadalafil (TD), a phosphodiesterase-5 (PDE-5) inhibitor with poor oral bioavailability. The aim of the study was to prepare and characterize three crystalline polymorphs of TD (II, III, and IV) and the tadalafil amorphous form (TD-AM). TD polymorphs and TD-AM were prepared and characterized by polarized light microscope (PLM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), X-ray powder diffractometry (XRPD), and Fourier-transform (FT)IR, followed by the dissolution testing, physical stabilities and polymorphic transformation studies. TD-I and TD-II were found to be enantiotropically related, while TD-III was monotiotropically related to TD-I with heat release. Among all studied polymorphs, TD-AM demonstrated an extremely high intrinsic dissolution rate with most prolonged higher saturated concentration during dissolution, while TD-II, TD-III, and TD-IV converted to TD-I easily by supersaturation-mediated phase transformation. Upon heating under 60°C for 3 h and storing at long-term stability condition for 3 months, no phase transformation was detected for TD-I, TD-III, and TD-AM, while TD-II and TD-IV easily transformed to TD-I and TD-III, respectively. The higher intrinsic dissolution rate, prolonged supersaturated state during dissolution and favorable physical stability of TD-AM made it to be a very promising candidate for further product development.

Effect of Crystal Habit on Intrinsic Dissolution Behavior of Celecoxib Due to Differential Wettability

Intrinsic dissolution rate (IDR) is a useful technique to differentiate the solid forms of a drug. In the present study, the impact of crystal habit and crystal size on IDR of celecoxib (CEL) in different media was assessed. The IDR of plate-shaped CEL crystals (CEL-P) (53.4 ± 6.7 μg/min/cm2) was 46.3% higher than that of acicular crystals (CEL-A) (36.5 ± 1.7 μg/min/cm2) in pH 12 phosphate buffer. Contact angle experiments and values of dispersive and polar components of surface free energy indicated better wettability of CEL-P compacts than CEL-A. Higher IDR and better wettability of CEL-P were attributed to favorable exposure of hydrophilic crystal facets on compact surface, due to preferred orientation during compaction. In contrast to native samples, milled CEL-A (MCEL-A) and milled CEL-P (MCEL-P) showed similar IDR. Interestingly, IDR of CEL-A (36.5 ± 1.7 μg/min/cm2) and MCEL-A (35.64 ± 5.09 μg/min/cm2) did not show any significant difference (p > 0.05). However, IDR of CEL-P (53.4 ± 6.7 μg/min/cm2) was significantly higher (p < 0.05) than that of MCEL-P (39.15 ± 2.48 μg/min/cm2). This was ascribed to (i) differential cleavage behavior of CEL-A and CEL-P during milling and (ii) reduced degree of preferred orientation of hydrophilic facets in MCEL-P compacts. This work provides an interesting case study of the impact of particle level properties and surface molecular environment on IDR.

Preparation of an amorphous sodium furosemide salt improves solubility and dissolution rate and leads to a faster Tmax after oral dosing to rats

Amorphous forms of furosemide sodium salt and furosemide free acid were prepared by spray drying. For the preparation of the amorphous free acid, methanol was utilised as the solvent, whereas the amorphous sodium salt was formed from a sodium hydroxide-containing aqueous solvent in equimolar amounts of NaOH and furosemide. Information about the structural differences between the two amorphous forms was obtained by Fourier Transform Infrared Spectroscopy (FTIR), and glass transition temperature (Tg) was determined using Differential Scanning Calorimetry (DSC). The stability and devitrification tendency of the two amorphous forms were investigated by X-ray Powder Diffraction (XRPD). The apparent solubility of the two amorphous forms and the crystalline free acid form of furosemide in various gastric and intestinal stimulated media was determined. Moreover, the dissolution characteristics of the two amorphous forms and of crystalline free acid were investigated.FTIR confirmed molecular differences between the amorphous free acid and salt. The amorphous salt showed a Tg of 101.2°C, whereas the Tg for the amorphous free acid was found to be 61.8°C. The amorphous free acid was physically stable for 4days at 22°C and 33% relative humidity (RH), while the amorphous salt exhibited physical stability for 291days at the same storage conditions. When storing the amorphous forms at 40°C and 75% RH both forms converted to crystalline forms after 2days.The apparent solubility of the amorphous salt form was higher than that of both amorphous and crystalline free acid in all media studied. All three forms of furosemide exhibited a greater solubility in the presence of biorelevant media as compared to buffer, however, an overall trend for a further increase in solubility in relation to an increase in media surfactant concentration was not seen. The amorphous salt demonstrated an 8- and 20-fold higher intrinsic dissolution rate (IDR) when compared to amorphous and crystalline free acid, respectively.The promising properties of the amorphous salt in vitro were further evaluated in an in vivo study, where solid dosage forms of the amorphous salt, amorphous and crystalline free acid and a solution of furosemide were administered orally to rats. The amorphous salt exhibited a significantly faster Tmax compared to the solution and amorphous and crystalline free acid. Cmax for the solution was significantly higher compared to the three furosemide forms. No significant difference was found in AUC and absolute bioavailability for the solution, crystalline free acid and the two amorphous forms of furosemide. It can be concluded that the higher IDR and higher apparent solubility of the amorphous salt resulted in a faster Tmax compared to the amorphous and crystalline free acid.

A new cocrystal and salts of itraconazole: Comparison of solid-state properties, stability and dissolution behavior

Cocrystallization and salt formation have been shown to entail substantial promise in tailoring the physicochemical properties of drug compounds, in particular, their dissolution and hygroscopicity. In this work, we report on the preparation and comparative evaluation of a new cocrystal of itraconazole and malonic acid and two new hydrochloric salts (dihydrochloride and trihydrochloride) of itraconazole. The intrinsic dissolution rate, hygroscopicity, and thermodynamic stability were determined for the obtained solid-state forms and compared to itraconazole-succinic acid (2:1) cocrystal. The results show that the solid-state forms with higher intrinsic dissolution rate are less stable. Both itraconazole salts exhibited the highest dissolution rate, but also demonstrated high hygroscopicity at relative humidity above 70%. The new cocrystal, in contrast, were found to increase the dissolution rate of the parent drug by about 5-fold without compromising the hygroscopicity and the stability. This study demonstrates that, for dissolution rate enhancement of poorly water-soluble weak bases, cocrystallization is a more suitable approach than hydrochloric salt formation.

A comparative assessment of solubility advantage from glassy and crystalline forms of a water-insoluble drug

The objective of the present study was to generate and characterize the glassy state of Irbesartan (IBS), with a view to exploit the solubility advantage from disordered high energy system. The major reason for limited solubility benefit from amorphous systems is their devitrification, on exposure to primarily aqueous dissolution medium. IBS is a lipophilic molecule and exhibits poor aqueous solubility and incomplete dissolution. IBS was found to be a good glass former (with glass transition/melting temperature >0.7), non-hygroscopic in nature and showed reasonable solid-state stability. The present work places particular emphasis on studying the influence of various dissolution environments on the devitrification of amorphous system. It was noted that IBS forms a relatively ‘stable’ glassy system with a 2.5-fold increase in aqueous solubility and a higher intrinsic dissolution rate (IDR). The dissolution behavior showed pH dependency and about eight-fold solubility advantage was obtained from amorphous system at pH 3. Both the crystalline and amorphous forms exhibited appreciably high solubility in HCl and HCl strength was found to significantly influence the solubility of crystalline form. Amorphous IBS showed reduced devitrification in HCl, as against water, thus highlighting the effect of dissolution environment on devitrification kinetics. Statistical and mathematical analyses were performed to compare the solubility advantage obtained using amorphous IBS vis-à-vis the crystalline counterpart.

Modification of acetaminophen crystals. II. Influence of stirring rate during solution-phase growth on crystal properties in the presence and absence of p-acetoxyacetanilide

Acetaminophen (P) crystals have been grown from pure aqueous solutions containing 0 and 500 mg · dm −3 p-acetoxyacetanilide (A) at various stirring speeds (200–400 rpm) and the physical properties examined. When A is omitted from the solutions, an increase of the stirring rate has no significant effects on the crystal habit (polyhedral prisms), but markedly raises the water content (by a factor of 10), lowers the enthalpy of fusion, ΔH f, melting point, ( igT m) and entropy of fusion, ΔS f, (by 8–18%, 0 respectively) and decreases and then increases the intrinsic dissolution rate ( IDR) of the P crystals. However, in the presence of A, the crystals assume an acicular morphology, independent of the agitation rate of the solutions. Whilst eliciting no further changes in the habit of these crystals, application of more vigorous stirring to the solutions leads to a moderate decrease in the uptake of A, a slight increase in water content, a slight decrease in the ΔH f, T m and ΔS f as well as an initial reduction and a su IDR. Compared with the polyhedral prisms crystallized in the absence of A, these crystals invariably demonstrate a considerably higher IDR, consistent with their needle-like habit and much lower water content. These observations demonstrate the pharmaceutical significance of agitation during crystallization in modulating the physical properties and aqueous dissolution rate of the P crystals.