Thermal Analysis Investigation of Dapoxetine and Vardenafil Hydrochlorides using Molecular Orbital Calculations

Application of Simultaneous and Coupled Thermal Analysis Techniques in Studies on the Melting Process, Course of Pyrolysis and Oxidative Decomposition of Fused Triazinylacetohydrazides

The effect of the structure of promising antioxidant agents with prospective medical use, i.e., unsubstituted and para-substituted annelated triazinylacetic acid hydrazides, on their melting points, thermal stabilities, pyrolysis and oxidative decomposition stages and the type of volatiles emitted under heating with the use of DSC and TG/DTG/FTIR/QMS methods was evaluated and discussed. The melting point of the investigated compounds increased with an enhanced number of electrons (directly correlated with their molecular weight). Melting enthalpy values were determined and presented for all the studied compounds. The pyrolysis and oxidative decomposition processes of the analysed molecules consisted of several poorly separated stages, which indicated a multi-step course of the decomposition reactions. It was found that the thermal stability of the tested compounds depended on the type of substituent at the para position of the phenyl moiety or its absence. In both atmospheres used (air and helium), the thermal stability increased in relation to R as follows: -CH3 ≤ -OCH3 < -H < -OC2H5. In an inert atmosphere, it was higher by approx. 8-18 °C than in an oxidative atmosphere. The pyrolysis was connected with the emission of NH3, HCN, HNCO, HCONH2, HCHO, CO2, CO and H2O in the case of all the tested compounds, regardless of the substituent attached. In the case of the derivative containing the para-CH3 group, para-toluidine was an additional emitted aromatic product. In turn, emissions of aniline and alcohol (methanol or ethanol) for compounds with the para-OCH3 and para-OC2H5 groups, respectively, were confirmed. In oxidative conditions, the release of NH3, NO, HCN, HNCO, HCONH2, CO2, H2O and cyanogen (for all the compounds) and para-toluidine (for the para-CH3 derivative), aniline (for para-OCH3, para-OC2H5 and unsubstituted derivatives) and acetaldehyde (for the para-OC2H5 derivative) were clearly observed. No alcohol emissions were recorded for either compound containing the para-OCH3- or para-OC2H5-substitututed phenyl ring. These results confirmed that the pyrolysis and oxidative decomposition of the investigated annelated triazinylacetohydrazides occurred according to the radical mechanism. Moreover, in the presence of oxygen, the reactions of volatiles and residues with oxygen (oxidation) and the combustion process additionally proceeded.

Experimental Studies on the Thermal Properties and Decomposition Course of a Novel Class of Heterocyclic Anticancer Drug Candidates

The experimental studies on the thermal properties and decomposition course of a novel class of potential anticancer drugs (1–5) containing in their heterobicyclic structures the asymmetrical triazine template were performed with the use of differential scanning calorimetry (DSC) and simultaneous thermogravimetry/differential scanning calorimetry (TG/DTG/DSC) coupled online with Fourier transform infrared spectroscopy (FTIR) and quadrupole mass spectrometry (QMS) in inert and oxidizing conditions. All the compounds were thermally characterized in detail for the first time in this article. The DSC studies proved that the melting points of the tested compounds depended on the position and type of the substituent at the phenyl moiety, whereas they did not depend on the furnace atmosphere. All the tested polynitrogenated heterocycles proved to be molecules with high thermal stability in both atmospheres, and most of them (1, 3–5) were more stable in oxidizing conditions, which indicated the formation of a more thermally stable form of the compounds when interacting with oxygen. The simultaneous TG/FTIR/QMS analyses confirmed that their pyrolysis process occurred in one main stage resulting in the emission of volatiles such as NH3, HNCO, HCN, CO, CO2, H2O, NO2, aromatic amine derivatives, alkenes (for compounds 1–5), and HCl (for the compound 5). On the other hand, the oxidative decomposition process was more complicated and proceeded in two main stages leading to the emission of NH3, CO2, CO, HCN, HNCO, H2O, some aromatics (for compounds 1–5), HCl (for compounds 3–5) as well as the additional volatiles such as N2, NO2, NH2OH, and (CN)2. The type of the formed volatiles indicated that the decomposition process of the studied heterocycles under the influence of heating was initiated by the radical mechanism. Their decomposition was related to the symmetric cleavage of C–N and C–C bonds (inert conditions) and additional reaction of the volatiles and residues with oxygen (oxidizing conditions).

Combinations of Freeze-Dried Amorphous Vardenafil Hydrochloride with Saccharides as a Way to Enhance Dissolution Rate and Permeability

To improve physicochemical properties of vardenafil hydrochloride (VAR), its amorphous form and combinations with excipients-hydroxypropyl methylcellulose (HPMC) and β-cyclodextrin (β-CD)-were prepared. The impact of the modification on physicochemical properties was estimated by comparing amorphous mixtures of VAR to their crystalline form. The amorphous form of VAR was obtained as a result of the freeze-drying process. Confirmation of the identity of the amorphous dispersion of VAR was obtained through the use of comprehensive analysis techniques-X-ray powder diffraction (PXRD) and differential scanning calorimetry (DSC), supported by FT-IR (Fourier-transform infrared spectroscopy) coupled with density functional theory (DFT) calculations. The amorphous mixtures of VAR increased its apparent solubility compared to the crystalline form. Moreover, a nearly 1.3-fold increase of amorphous VAR permeability through membranes simulating gastrointestinal epithelium as a consequence of the changes of apparent solubility (P_{app crystalline VAR} = 6.83 × 10^-6 cm/s vs. P_{app amorphous VAR} = 8.75 × 10^-6 cm/s) was observed, especially for its combinations with β-CD in the ratio of 1:5-more than 1.5-fold increase (P_{app amorphous VAR} = 8.75 × 10^-6 cm/s vs. P_{app amorphous VAR:β-CD 1:5} = 13.43 × 10^-6 cm/s). The stability of the amorphous VAR was confirmed for 7 months. The HPMC and β-CD are effective modifiers of its apparent solubility and permeation through membranes simulating gastrointestinal epithelium, suggesting a possibility of a stronger pharmacological effect.

Two-Step Optimization to Develop a Transdermal Film Loaded With Dapoxetine Nanoparticles: A Promising Technique to Improve Drug Skin Permeation

Dapoxetine (DPX) is an orally administered drug for the treatment of premature ejaculation (PE). One of the challenges of administering DPX orally as a tablet is its poor bioavailability (ie, 42%) due to extensive first-pass metabolism. Thus, it is vital to develop a new formulation and mode of delivery to achieve the unmet needs of PE treatment. In this study, an optimized DPX polymeric nanoparticle (PNP) was developed and subsequently loaded into a transdermal film. The Box–Behnken design was utilized to optimize 3 formulation factors affecting the particle size and entrapment efficiency (EE) of chitosan (CS)-alginate (ALG) PNPs. A 3-level factorial design was used to study the effect of 2 variables affecting DPX cumulative percent released and percent elongation from transdermal films loaded with DPX-PNPs. Permeation parameters were calculated following ex vivo permeation study through rat skin. Transport of the PNPs across the skin layers was investigated using a fluorescence laser microscope. Results revealed that an optimized PNPs formulation was developed with a particle size 415.94 nm and EE 37.31%. Dapoxetine was successfully entrapped in the polymeric matrix. Chitosan and ALG interacted electrostatically with the studied cross-linking agents to form a polyelectrolyte complex. The ex vivo study illustrated a sustained release profile of DPX with enhanced skin permeation from the film loaded PNPs. Moreover, the PNPs was able to penetrate deeper into skin layers. Therefore, DPX transdermal film developed in this work could be considered as a successful drug delivery with better patient compliance for the treatment of PE.

Novel Enhanced Therapeutic Efficacy of Dapoxetine HCl by Nano-Vesicle Transdermal Gel for Treatment of Carrageenan-Induced Rat Paw Edema

The aim of this was to develop a well-balanced, replaceable, and patient non-infringing innovative transdermal drug delivery system "nano-vesicle transdermal gel" (NVTG) approaches for inhibiting inflammation. To consummate this objective, we developed a skin permeation nanogel system containing surface active agent along with ethanol. Carbopol 971p, hydroxypropyl methyl cellulose (HPMC K15M), and chitosan were used to fabricate the nanogels. The nanogel system was evaluated for pH, content uniformity, spreadability, rheological studies, in vitro skin permeation, and drug release. Carbapol 971p with the desired in vitro skin permeation was utilized to investigate skin irritation test and effects on inflammation using acute inflammatory paw edema models. Moreover, in vivo pharmacokinetic study was assessed. pH of this nanogels was found within the range of 6.1-7.2, whereas the viscosity was found 310.13 to 6361 cps. The ex vivo skin permeation gels showed permeation flux range, 5.9 ± 0.80 to 17.92 ± 1.13 μg/cm² h. The highest permeation flux (17.92 ± 1.13 μg/cm² h) was observed, which was 3.14-folds higher than that of the plain DH gel (10.72 ± 0.84 μg/cm² h. Additionally, from toxicological study, no obvious signs of toxicity such as skin irritation (of laboratory rats) were identified. The in vivo anti-inflammatory behavior in carrageenan-induced rats showed comparatively higher inhibition of rat paw edema swelling by the prepared nanogel compared to that of the plain DH gel and marketed ibuprofen over 6 h. The amount of drug accumulated in the skin after topical application was much higher than oral application. In conclusion, developed NVTG formulation loaded with dapoxetine HCl (DH) offers new opportunities for creating novel therapeutic modality for inflammation patients with fewer adverse effects.

Mitigation of Rheumatic Arthritis in a Rat Model via Transdermal Delivery of Dapoxetine HCl Amalgamated as a Nanoplatform: In vitro and in vivo Assessment

Purpose

Dapoxetine HCl (DH), a selective serotonin reuptake inhibitor, may be useful for the treatment of rheumatic arthritis (RA). The purpose of this study was to investigate the therapeutic efficacy of transdermal delivery of DH in transethosome nanovesicles (TENVs). This novel delivery of DH may overcome the drawbacks associated with orally administered DH and improve patient compliance.

Methods

DH-TENV formulations were prepared using an injection- sonication method and optimized using a 3³ Box-Behnken-design with Design Expert^® software. The TENV formulations were assessed for entrapment efficiency (EE-%), vesicle size, zeta potential, in vitro DH release, and skin permeation. The tolerability of the optimized DH-TENV gel was investigated using a rat skin irritation test. A pharmacokinetic analysis of the optimized DH-TENV gel was also conducted in rats. Moreover, the anti-RA activity of the optimized DH-TENV gel was assessed based on the RA-specific marker anti-cyclic cirtullinated peptide antibody (anti-CCP), the cartilage destruction marker cartilage oligomeric matrix protein (COMP) and the inflammatory marker interleukin-6 (IL-6). Level of tissue receptor activator of nuclear factor kappa-Β ligand (RANKL) were also assessed.

Results

The optimized DH-TENV formulation involved spherical nanovesicles that had an appropriate EE- % and skin permeation characteristic. The DH-TENV gel was well tolerated by rats. The pharmacokinetics analysis showed that the optimized DH-TENV gel boosted the bioavailability of the DH by 2.42- and 4.16-fold compared to the oral DH solution and the control DH gel, respectively. Moreover, it significantly reduced the serum anti-CCP, COMP and IL-6 levels and decreased the RANKL levels. Furthermore, the DH-TENV gel attenuated histopathological changes by almost normalizing the articular surface and synovial fluid.

Conclusion

The results indicate that DH-TENVs can improve transdermal delivery of DH and thereby alleviate RA.

Study of Thermal Analysis Behavior of Fenbendazole and Rafoxanide

Purpose: Thermal analysis techniques have been applied to study the thermal behavior of fenbendazole (Fen) and rafoxanide (Raf). Semi-empirical molecular orbital calculations were used to confirm these results. Methods: Thermogravimetric analysis, derivative thermogravimetry, differential thermal analysis and differential scanning calorimetry were used to determine the thermal behavior and purity of the drugs under investigation. Results: Thermal behavior of Fen and Raf were augmented using semi-empirical molecular orbital calculations. The purity values were found to be 99.17% and 99.60% for Fen and Raf, respectively. Conclusion: Thermal analysis techniques gave satisfactory results to obtain quality control parameters such as melting point and degree of purity at low cost, furthermore, its simplicity and sensitivity justifies its application in quality control laboratories.

Spectroscopic and Spectrometric Methods Used for the Screening of Certain Herbal Food Supplements Suspected of Adulteration

Purpose: This study was carried out in order to find a reliable method for the fast detection of adulterated herbal food supplements with sexual enhancement claims. As some herbal products are advertised as "all natural", their "efficiency" is often increased by addition of active pharmaceutical ingredients such as PDE-5 inhibitors, which can be a real health threat for the consumer.

Methodes: Adulterants, potentially present in 50 herbal food supplements with sexual improvement claims, were detected using 2 spectroscopic methods - Raman and Fourier Transform Infrared - known for reliability, reproductibility, and an easy sample preparation. GC-MS technique was used to confirm the potential adulterants spectra.

Results: About 22% (11 out of 50 samples) of herbal food supplements with sexual enhancement claims analyzed by spectroscopic and spectrometric methods proved to be "enriched" with active pharmaceutical compounds such as: sildenafil and two of its analogues, tadalafil and phenolphthalein. The occurence of phenolphthalein could be the reason for the non-relevant results obtained by FTIR method in some samples. 91% of the adulterated herbal food supplements were originating from China.

Conclusion: The results of this screening highlighted the necessity for an accurate analysis of all alleged herbal aphrodisiacs on the Romanian market. This is a first such a screening analysis carried out on herbal food supplements with sexual enhancement claims.

Thermal analyses of some fluoroquinolone pharmaceutical compounds in comparison with molecular orbital calculations

The thermal behavior and stability of some drugs, such as SPAR, BESI and GEM, were investigated.