Identification of Sildenafil Compound in Selected Drugs Using X-ray Study and Thermal Analysis.

Twelve drugs containing sildenafil compounds (sildenafil citrate and sildenafil base) were examined using X-ray studies and thermal analysis. According to the manufacturer's information, the presence of sildenafil was confirmed in all investigated drugs. The positions of diffraction lines (value of 2θ angle) agree with the patterns presented in the ICDD database, Release 2018 (ICDD-International Centre of Diffraction Data). The difference expresses the agreement in the position of the diffraction line between the tested substance and the standard. A good agreement is when this difference is less than 0.2°. The values of interplanar distances dhkl are also compatible with the ICDD database. It indicated that the drug examined was genuine. Because all drugs are mixtures of different substances (API and excipients), the various diffraction line intensities were detected in all observed X-ray images for the tested drugs. The intensity of the diffraction line depends on many factors, like the amount of substance, coexisting phases, and mass absorption coefficient of the mixture. The thermal analysis confirmed the results obtained by the X-ray study. On DSC curves, the endothermic peaks for sildenafil compounds were observed. The determined melting points of sildenafil compounds corresponded to the values available in the literature. The results gathered by connecting two methods, X-ray study and thermal analysis, can help identify irregularities that may exist in pharmaceutical specimens, e.g., distinguishing genuine from counterfeit products, the presence of a correct polymorph, a lack of active substance, an inaccurate amount of the active substance, or excipients in the tested drug.

Fast and semiquantitative screening for sildenafil in herbal over-the-counter formulations with atmospheric pressure solid analysis probe (ASAP) to prevent medicinal adulteration.

Herbal medicines are commonly used in many countries all around the world. In Western countries they are now gaining more and more popularity, whereas in countries like China and India they have been entrenched for millenniums. Some of these perceived herbal medicines claim to help when suffering from erectile dysfunction. Nevertheless, many of these products are adulterated with PDE5 inhibitors like sildenafil or α-blockers. Patients who suffer from high blood pressure sometimes resort to herbal products, as they are not allowed to take sildenafil because of negative drug-drug interactions with nitrates (often utilized as treatment for coronary diseases). Products which are then adulterated with PDE5 inhibitors, can seriously harm patients. Therefore, this study reports the instant screening of alleged herbal products by employing atmospheric pressure solids analysis probe and high-resolution mass spectrometry to determine adulterants. Three out of 12 investigated products contained sildenafil in ranges from 0.5% to 18%. Multivariate analysis of ambient mass spectrometry measurements revealed encouraging outcomes for distinguishing non-sildenafil and sildenafil adulterated samples. Atmospheric pressure solids analysis probe is therefore a promising method for the rapid determination of sildenafil in herbal products with possible downstream semiquantitative analysis.

Synthesis and properties of sildenafil isostere.

A series of novel pyrazolo[3,4-d]pyrimidin-4-one derivatives were synthesized and evaluated for their anti-phosphodiesterase-5 (PDE-5) activity. A total of 28 compounds, containing alkyl and aryl groups at the 1-N and 3-C positions on the pyrazole ring, and also bearing different alkyl substituents on the piperazine ring were synthesized. Four compounds (4d, 5d, 6d, and 5o) were found to have better inhibitory activity against PDE-5 (IC50 < 10 nM). All four of the most active compounds contain a phenyl ring at the N1 position. Compounds containing a 3,5-dimethylpiperazinyl group show better activity than others. These results suggest that compound 5o can be used as a lead structure for developing new inhibitors of PDE-5.

Detection Method of Falsified Medicines by Using a Low-Cost Raman Scattering Spectrometer Combined with Soft Independent Modeling of Class Analogy and Partial Least Squares Discriminant Analysis.

There are many reports of falsified medicines that may cause harm to patients. A rapid and simple method of identifying falsified medicines that could be used in the field is required. Although Raman scattering spectroscopy has become popular as a non-destructive analysis, few validation experiments on falsified medicines that are actually distributed on the market have been conducted. In this study, we validated a discriminant analysis using an ultra-compact, portable, and low-cost Raman scattering spectrometer combined with multivariate analysis. The medicines were three types of erectile dysfunction therapeutic tablet and one type of antifungal tablet: tadalafil (Cialis), vardenafil hydrochloride (Levitra), sildenafil citrate (Viagra), and fluconazole (Diflucan), which is sometimes advertised as female Viagra. For each medicine, the authentic standard product and products obtained by personal import via the internet (genuine or falsified) were used. Discriminant analyses were performed on the Raman spectra combined with soft independent modeling of class analogy (SIMCA) and partial least squares discriminant analysis (PLS-DA). It was possible to identify all falsified samples by SIMCA using the standard product model for all four products. Using the PLS-DA using the PLS models of the four standard products, falsified Levitra and Diflucan samples were classified correctly, although some falsified Cialis and all Viagra samples also belonged to the standard class. In this study, SIMCA might be more suitable than PLS-DA for identifying falsified medicines. A spectroscopic module that combines the low-cost Raman scattering spectroscopy with SIMCA might contribute to the rapid identification of falsified medicines in the field.

Development of a group-specific antibody-based immunoassay method for simultaneously detecting sildenafil-like adulterants in herbal spirit drinks.

Phosphodiesterase type 5 (PDE-5) inhibitors are commonly used to treat erectile dysfunction. There is a problem with synthesis and illegal use of a wide range of analogues of the licenced drugs and a simple class-wide analytical method is required. In this work, based on structural modelling, we developed an immunological method using norneovardenafil as a hapten as it contains only the general sub-structure and the common features of sildenafil-like adulterants, such as hydrophobic centres, hydrogen-bond donor atoms and hydrogen-bond acceptor atoms. Thus theoretically it could induce production of antibody which could recognise multiple sildenafil-like adulterants. By immunising rabbits, a group-specific polyclonal antibody was obtained with the desired broad-spectrum molecular recognition performance against sildenafil-like adulterants. Then, an indirect competitive enzyme-linked immunosorbent assay (icELISA) was developed for the detection of sildenafil-like adulterants in herbal spirit drinks. Under the optimised conditions, the icELISA method showed broad linear ranges for acetildenafil, sildenafil and vardenafil respectively of 0.7 to 27.7 µg/kg, 1.0 to 70.7 µg/kg and 1.5 to 22.7 µg/kg, with half-maximal inhibition concentration (IC50) values of 4.5 µg/kg, 8.3 µg/kg and 5.7 µg/kg, respectively. For eleven herbal spirit drinks, there was good agreement between total levels of sildenafil-like adulterants measured by icELISA and levels of each of four individual adulterants determined by LC-MS/MS. In short, the developed icELISA can be employed for rapid and simple screening for adulteration of herbal spirit drinks with sildenafil-like compounds.

Structural Determination, Biological Function, and Molecular Modelling Studies of Sulfoaildenafil Adulterated in Herbal Dietary Supplement.

Unapproved ingredients included in herbal medicines and dietary supplements have been detected as adulterated synthetic drugs used for erectile dysfunction. Extraction from a dietary supplement was performed to isolate the compounds by HPLC analysis. The structural characterization was confirmed using mass spectrometry (ESI-TOF/MS and LC-MS/MS), 1H NMR, and 13C NMR spectroscopy techniques. Results identified the thus-obtained compound to be sulfoaildenafil, a thioketone analogue of sildenafil. The biological activities of this active compound have been focused for the first time by the experimental point of view performance in vitro. The results revealed that sulfoaildenafil can affect the therapeutic level of nitric oxide through the upregulation of nitric oxide synthase and phosphodiesterase type 5 (PDE5) gene expressions. This bulk material, which displays structural similarity to sildenafil, was analyzed for the presence of a PDE5 inhibitor using a theoretical calculation. These unique features of the potential activity of PDE5 protein and its inhibitors, sildenafil and sulfoaildenafil, may play a key consideration for understanding the mode of actions and predicting the biological activities of PDE5 inhibitors.

Studies on metal-organic framework (MOF) nanomedicine preparations of sildenafil for the future treatment of pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is an incurable disease, although symptoms are treated with a range of dilator drugs. Despite their clinical benefits, these drugs are limited by systemic side-effects. It is, therefore, increasingly recognised that using controlled drug-release nanoformulation, with future modifications for targeted drug delivery, may overcome these limitations. This study presents the first evaluation of a promising nanoformulation (highly porous iron-based metal-organic framework (MOF); nanoMIL-89) as a carrier for the PAH-drug sildenafil, which we have previously shown to be relatively non-toxic in vitro and well-tolerated in vivo. In this study, nanoMIL-89 was prepared and charged with a payload of sildenafil (generating Sil@nanoMIL-89). Sildenafil release was measured by Enzyme-Linked Immunosorbent Assay (ELISA), and its effect on cell viability and dilator function in mouse aorta were assessed. Results showed that Sil@nanoMIL-89 released sildenafil over 6 h, followed by a more sustained release over 72 h. Sil@nanoMIL-89 showed no significant toxicity in human blood outgrowth endothelial cells for concentrations up to100µg/ml; however, it reduced the viability of the human pulmonary artery smooth muscle cells (HPASMCs) at concentrations > 3 µg/ml without inducing cellular cytotoxicity. Finally, Sil@nanoMIL-89 induced vasodilation of mouse aorta after a lag phase of 2-4 h. To our knowledge, this study represents the first demonstration of a novel nanoformulation displaying delayed drug release corresponding to vasodilator activity. Further pharmacological assessment of our nanoformulation, including in PAH models, is required and constitutes the subject of ongoing investigations.

Discovery of two novel hetero-tricyclic lead scaffolds as PDE5A inhibitor: virtual screening, molecular docking and pharmacophore modeling approach.

Phosphodiesterase 5A enzyme has been the upcoming and promising target in hypertension management. In this research, reported 270 bioactive natural products having antihypertensive potential were selected and docked against PDE5A using vLife MDS 4.6 software. Based on docking score, π-stacking, H-bond and ionic interactions with PDE5A, 82 tricyclic compounds were selected for further study. Protein residue Gln817A was associated in H-boding, Leu804A in ionic interaction whereas Val782A and Phe820A were associated in π-stacking interaction with ligand. In silico docking studies resulted in discovery of oxygen containing naphthofuran and nitrogen and oxygen containing pyrano quinolizine tricyclic lead scaffolds as novel PDE5A inhibitors. Additionally, developed pharmacophore model suggested that one centre of hydrogen bond acceptor, one aromatic centre and two aliphatic centres are minimum pharmacophoric features required in the molecule so as to show sildenafil like activity. The identified lead scaffolds would provide novel platform for drug discovery of bioactive natural products.

UHPLC for quality evaluation of genuine and illegal medicines containing sildenafil citrate and tadalafil.

One of the highest incidences of illegal drug products is related to phosphodiesterase-5 inhibitors, used in treatment of erectile dysfunction, including those containing sildenafil citrate and tadalafil. In this context, comprehensive evaluation of the quality of genuine and illegal medicines was performed. A simple and rapid ultra-high performance liquid chromatography (UHPLC-UV) method to quantify sildenafil and tadalafil in the presence of six degradation products was developed and validated. Sildenafil and tadalafil were submitted to forced degradation. The separation was carried out on a Kinetex C18 (50 × 2.1 mm; 1.7 µm) column with mobile phase composed of acetonitrile and aqueous triethylamine solution. The calibration curves were linear in the range of 14-126 µg mL-1 for sildenafil citrate and 4-36 µg mL-1 for tadalafil and the method proved to be selective, precise, accurate and robust. Sildenafil degraded in oxidative media, whereas tadalafil degraded in acidic, alkaline and oxidative environment. The chemical structures and the mechanisms for the formation of the main degradation products were proposed by UHPLC coupled to tandem mass spectrometry. The UHPLC-UV method was applied in the pharmaceutical analysis of genuine and seized medicines. Some of them did not meet quality standards, mainly due to contents below specifications and the large variation on contents between units within a batch.

Oleosomes Encapsulating Sildenafil Citrate as Potential Topical Nanotherapy for Palmar Plantar Erythrodysesthesia with High Ex vivo Permeation and Deposition.

Palmar plantar erythrodysesthesia (PPE) is a commonly reported skin toxicity of chemotherapeutic agents that significantly affects patients' quality of life. PPE is described as inflammation, swelling, and even cracks and ulcers in the skin of palms and soles of the feet. Conventional treatment includes topical creams, analgesics, or corticosteroids. However, serious cases are not responding to these medications. PPE has been reported to cause drug cessation or dose reduction if not properly treated. Sildenafil citrate (SC) has a well-documented activity in wound healing through improving blood supply to the affected area. However, SC has poor physicochemical properties limiting its transdermal permeation and deposition. This research endeavored to elaborate novel vesicular system with natural components, phospholipids and oleic acid, loaded with sildenafil citrate for topical management of PPE. Sildenafil-loaded oleosomes were prepared using modified ethanol injection method. Optimized oleosomes had nanometric particle size (157.6 nm), negative zeta potential (- 85.2 mv), and high entrapment efficiency (95.56%). Ex vivo studies on human skin revealed that oleosomes displayed 2.3-folds higher permeation and 4.5-folds more deposition through the human skin compared to drug suspension. Results endorsed SC oleosomes as suitable topical treatment of PPE providing ameliorated sildenafil permeability in addition to acting as a reservoir for gradual release of the drug. Graphical abstract.

Orphan Formulations for Pediatric Use: Development and Stability Control of Two Sildenafil Citrate Solutions for the Treatment of Pulmonary Hypertension.

Sildenafil citrate causes vasodilatation, relaxation of the smooth muscle, and reduction of pulmonary arterial pressure. The latter property makes sildenafil citrate efficient for the treatment of cardiovascular diseases, including pulmonary arterial hypertension. Pediatric patients with pulmonary arterial hypertension are more susceptible to errors in drug administration than adults because of a lack of suitable drug dosages. Thus, the purpose of this study was to develop stable (chemically and microbiologically) sildenafil citrate drop liquid formulation, suitable for pediatric patients (including diabetics), ensuring safety during preparation and storing and improving palatability by using milk as a carrier for administration. The significant factors that affect the sildenafil solubility were evaluated by applying a Plackett-Burman design using two levels with six variables. The experiment showed that the type of buffer and glycerin content influenced the sildenafil solubility. The developed formulations proved to be stable for 6 months at all three assayed conditions (40± 2°C, 75 ± 5% RH; 25± 2°C, 60 ± 5% RH; and 4 ± 2°C). The microbiological tests fit with the requirement of the pharmacopeia at day 0 and 90 and even more at day 180. Finally, the palatability assay showed that 0.82 mL of the formulation containing buffer phosphate, 20% glycerin, and 4 mg mL-1 of sildenafil citrate diluted in 4.8 mL milk (which fits the medium pediatric dose) presented similar palatability to milk alone, and no precipitate or turbidity was observed. Graphical abstract.

Enhanced nanoparticle accumulation by tumor-acidity-activatable release of sildenafil to induce vasodilation.

Inefficient nanoparticle accumulation in solid tumors hinders the clinical translation of cancer nanomedicines. Herein, we proposed that sildenafil, a vasodilator ampholyte, could be used to promote nanoparticle accumulation by inducing vasodilation after its tumor acidity-triggered release from the nanocarriers. To confirm this, sildenafil was first encapsulated in a cisplatin-incorporated polymeric micelle. The dense PEG shell of the micelle reduced its endocytosis by cancer cells, which in return resulted in accumulative extracellular release of protonated sildenafil in the acidic tumor microenvironment. The released sildenafil was found to be more effective in enlarging the tumor blood vessels than could be achieved without sildenafil. As a result, we demonstrated considerable improvement in the intratumoral accumulation of the sildenafil-cisplatin co-loaded nanoparticle and its enhanced cancer therapeutic efficacy over the control group. Given the generality of a dense PEG shell and a hydrophobic part in most clinically developed nanomedicines, this work implies the great potential of sildenafil as a simple and universal adjuvant to selectively promote the intratumoral accumulation of nanomedicines, thus improving their clinical translation.

Simultaneous analysis of 31 anti-impotence compounds potentially illegally added to herbal-based dietary supplements by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry.

In this paper, an ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF HRMS) method was developed and validated for screening, confirmation and quantitation of 31 anti-impotence compounds potentially illegally added to herbal-based dietary supplements. The analytes were well separated by the mobile phase consisted of 0.1% formic acid solution and acetonitrile with gradient elution at a flow rate of 0.3 mL/min. The MS analysis was operated in positive mode and the mass error of the 31 compounds were below 2.9 ppm. The method validation showed good linearity with coefficients of determination (r2) higher than 0.9973 for all analytes. LODs and LLOQs ranged from 0.005 to 0.50 µg/g or µg /mL and from 0.02 to 1.24 µg /g or µg/mL, respectively. The accuracy was in the range of 86.6% to 113.7%, while the intra-and inter-day precision were in the ranges of 0.9-7.6% and 0.9-11.4%, respectively. The absolute and relative matrix effect were in the range of 65.8-115.6% and 0.6-13.3%. The mean recoveries were in the range of 80.5-116.9%. The stability ranged from 0.4% to 8.5%. Among 200 batches of herbal-based dietary supplements, sildenafil and/or tadalafil were found to be added illegally in two samples, while not very high concentration of icariin was detected in one sample. The Q-TOF mass spectrometry has been proved to be a very powerful and efficient tool for rapid screening of 31 anti-impotence compounds potentially illegally added to herbal-based dietary supplements, ensuring food safety and public health.

Differentiation of human neuroblastoma cell line IMR-32 by sildenafil and its newly discovered analogue IS00384.

Sildenafil, a phosphodiesterase-5 inhibitor is FDA approved drug against erectile dysfunction. It is currently undergoing many clinical trials, alone or in combinations against different diseases. Treatment of neural progenitor cells with sildenafil is known to regulate their basal cGMP levels and enhance neurogenesis and differentiation. cGMP as well as cAMP are known to play a central role in the maintenance, repair and remodelling of the nervous system. In the present study, we report the neurodifferentiation property of sildenafil in neuroblastoma cancer cell line IMR-32. Sildenafil was found to induce the formation of neurite outgrowths that were found expressing neuronal markers, such as NeuN, NF-H and ßIII tubulin. IS00384, a recently discovered PDE5 inhibitor by our laboratory, was also found to induce neurodifferentiation of IMR-32 cells. The effect of IS00384 on differentiation was even more profound than sildenafil. Both the compounds were found to elevate and activate the Guanine nucleotide exchange factor C3G, which is a regulator of differentiation in IMR-32 cells. They were also found to elevate the levels of cGMP and activate the AMPK-ACC and PI3K-Akt signalling pathways. These pathways are known to play important role in cytoskeletal rearrangements necessary for differentiation. This study highlights the role of phosphodiesterases-5 in neurodifferentiation and use of sildenafil and IS00384 as small molecule tools to study the process of cellular differentiation.

A Multi-Biochemical and In Silico Study on Anti-Enzymatic Actions of Pyroglutamic Acid against PDE-5, ACE, and Urease Using Various Analytical Techniques: Unexplored Pharmacological Properties and Cytotoxicity Evaluation.

In the current study, pyroglutamic acid (pGlu), a natural amino acid derivative, has efficiently inhibited the catalytic activities of three important enzymes, namely: Human recombinant phosphodiesterase-5A1 (PDE5A1), human angiotensin-converting enzyme (ACE), and urease. These enzymes were reported to be associated with several important clinical conditions in humans. Radioactivity-based assay, spectrophotometric-based assay, and an Electrospray Ionization-Mass Spectrometry-based method were employed to ascertain the inhibitory actions of pGlu against PDE5A1, ACE, and urease, respectively. The results unveiled that pGlu potently suppressed the activity of PDE5A1 (half-maximal inhibitory concentration; IC50 = 5.23 µM) compared with that of standard drug sildenafil citrate (IC50 = 7.14 µM). Moreover, pGlu at a concentration of 20 µg/mL was found to efficiently inhibit human ACE with 98.2% inhibition compared with that of standard captopril (99.6%; 20 µg/mL). The urease-catalyzed reaction was also remarkably inactivated by pGlu and standard acetohydroxamic acid with IC50 values of 1.8 and 3.9 µM, respectively. Remarkably, the outcome of in vitro cytotoxicity assay did not reveal any significant cytotoxic properties of pGlu against human cervical carcinoma cells and normal human fetal lung fibroblast cells. In addition to in vitro assays, molecular docking analyses were performed to corroborate the outcomes of in vitro results with predicted structure-activity relationships. In conclusion, pGlu could be presented as a natural and multifunctional agent with promising applications in the treatment of some ailments connected with the above-mentioned anti-enzymatic properties.

Development of nanodispersion-based sildenafil metered-dose inhalers stabilized by poloxamer 188: a potential candidate for the treatment of pulmonary arterial hypertension.

Objectives: This study aims to formulate nanodispersion-based sildenafil metered-dose inhalers (MDIs) by using poloxamer 188 (P188) as a stabilizer; to evaluate their stability, aerosol characteristics, cytotoxicity, and inflammatory effects; and to investigate the effects of P188 on stability and aerosol characteristics of the MDIs. Methods: The stability and uniformity of the formulations were evaluated by high-performance liquid chromatography method. The aerosol characteristics were evaluated by the Next Generation Impactor. The cytotoxicity and inflammatory effects on respiratory epithelial cells and alveolar macrophages were evaluated by MTT assay and TNF-α, IL-1ß, and NO assay, respectively. Results: The optimal formulation was stable and well-uniform after 6 months. The fine particle fraction and mass median aerodynamic diameter (MMAD) of the formulation were 61.9% ± 2.5% and 1.69 ± 0.06 µm, respectively. The formulation was found to be nontoxic to respiratory epithelial cells and did not induce the inflammatory responses of alveolar macrophages. A positive correlation between P188 concentration and MMAD of the MDIs was observed. P188 possesses an ability to prevent the growth of sildenafil citrate monohydrate crystals in the formulations. Conclusions: The findings provided a basis for the development of sildenafil MDI as a potential candidate for the treatment of pulmonary arterial hypertension.

Phenytoin/sildenafil loaded poly(lactic acid) bilayer nanofibrous scaffolds for efficient orthopedics regeneration.

Autologous and synthetic bone grafts showed some limitations during their usage in bone tissue regeneration. This is attributed to several drawbacks such as difficulty of finding a donor in addition to the autoimmune rejection. This study aims to fabricate a well-designed biocompatible double-layered structure of highly porous poly(lactic acid)-based electrospun nanofibers (NFs) as scaffolds for bone tissue regeneration. Poly(lactic acid) was chosen to fabricate the main matrix of the NFs scaffold as it is one of the FDA approved and highly recommended biopolymers for biomedical applications owing to its high biodegradability and biocompatibility Each layer is loaded with a different drug (Phenytoin and Sildenafil) to stimulate bone healing process. The solvents and the parameters of electrospinning were manipulated to produce highly porous structures in order to enhance the in-situ biodegradability of the NFs mats as well as the drug release rate. The produced NFs mats were fully characterized morphologically (SEM), chemically (FTIR), physically (DSC) and physicochemically (biodegradability, swellability, porosity and water vapor permeability) as well as studying the drug release profiles of both drugs. Cytotoxicity of the fabricated NFs was tested using fibroblast cells to detect their biocompatibility. Cell adhesion and proliferation were examined using SEM before using the NFs as scaffolds in mice animal model. The efficiency of the developed NFs scaffolds in healing bone fractures was assessed after 14 and 28 days through visual inspection, SEM investigation and bone mineral density assessment. Finally, sections from the bone fracture sites were isolated for histopathological examination. The study revealed the efficiency of the drugs-loaded NFs in enhancing cell adherence, cell proliferation, angiogenesis formation and finally tissue restoration of bone fractures.

Analysis of Sildenafil in Liquor and Health Wine Using Surface Enhanced Raman Spectroscopy.

The illegal adulteration of sildenafil in herbal food supplements and alcoholic drinks immensely threatens human health due to its harmful side-effects. Therefore, it is important to accurately detect and identify the presence of sildenafil in alcoholic drinks. In this study, Opto Trace Raman 202 (OTR 202) was used as surface enhanced Raman spectroscopy (SERS) active colloids to detect sildenafil. The results demonstrated that the Raman enhancement factor (EF) of OTR 202 colloids reached 1.84 × 107 and the limits of detection (LODs) of sildenafil in health wine and liquor were found to be as low as 0.1 mg/L. Moreover, the SERS peaks of 645, 814, 1235, 1401, 1530 and 1584 cm-1 could be qualitatively determined as sildenafil characteristic peaks and the relationship between Raman peak intensity and sildenafil concentration in health wine and liquor were different. There was a good linear correlation between Raman peak intensity, and sildenafil concentration in health wine ranged 0.1-1 mg/L (0.9687< R2 < 0.9891) and 1-10 mg/L (0.9701 < R2 < 0.9840), and in liquor ranged 0.1-1 mg/L (0.9662 < R2 < 0.9944) and 1-20 mg/L (0.9625 < R2 < 0.9922). The relative standard deviations (RSD) were less than 5.90% (sildenafil in health wine) and 9.16% (sildenafil in liquor). The recovery ranged 88.92-104.42% (sildenafil in health wine) and 90.09-104.55% (sildenafil in liquor). In general, the sildenafil in health wine and liquor could be rapidly and quantitatively determined using SERS technique, which offered a simple and accurate alternative for the determination of sildenafil in alcoholic drinks.

Rapid and Quantitative Determination of Sildenafil in Cocktail Based on Surface Enhanced Raman Spectroscopy.

Sildenafil (SD) and its related compounds are the most common adulterants found in herbal preparations used as sexual enhancer or man's virility products. However, the abuse of SD threatens human health such as through headache, back pain, rhinitis, etc. Therefore, it is important to accurately detect the presence of SD in alcoholic beverages. In this study, the Opto Trace Raman 202 (OTR 202) was used as a surface-enhanced Raman spectroscopy (SERS) active colloids to detect SD. The results demonstrated that the limit of detection (LOD) of SD was found to be as low as 0.1 mg/L. Moreover, 1235, 1401, 1530, and 1584 cm-1 could be qualitatively determined as SD characteristic peaks. In a practical application, SD in cocktail could be easily detected using SERS based on OTR 202. Also, there was a good linear correlation between the intensity of Raman peaks at 1235, 1401, 1530, and 1584 cm-1 and the logarithm of SD concentration in cocktail was in the range of 0.1-10 mg/L (0.9822 < R2 < 0.9860). The relative standard deviation (RSD) was less than 12.7% and the recovery ranged from 93.0%-105.8%. Moreover, the original 500-1700 cm-1 SERS spectra were pretreated and the partial least squares (PLS) was applied to establish the prediction model between SERS spectra and SD content in cocktail and the highest determination coefficient (Rp2) reached 0.9856. In summary, the SD in cocktail could be rapidly and quantitatively determined by SERS, which was beneficial to provide a rapid and accurate scheme for the detection of SD in alcoholic beverages.

Design and evaluation of novel inhalable sildenafil citrate spray-dried microparticles for pulmonary arterial hypertension.

Pulmonary delivery of vasodilators is a promising alternative for the intravenous and oral treatment of pulmonary arterial hypertension (PAH). The aim of this study was to design and evaluate hydrogel microparticles as a carrier for sustained pulmonary delivery of sildenafil citrate. Spray dried hydrogel microparticles containing biodegradable sodium carboxymethyl cellulose, sodium alginate, and sodium hyaluronate polymers at variable concentrations were prepared. A design of experiment using the "Extreme Vertices Mixture" design was executed. The design was used to study the influence of polymer concentration and their interactions on the physicochemical properties of the formulations in terms of particle size, particle size distribution, product yield, entrapment efficiency, and in-vitro drug release. Selected formulations were also evaluated for swelling, biodegradation, moisture content, in-vitro aerodynamic performance, and cytotoxicity. In addition, a lung deposition and pharmacokinetic study was conducted in rats to study drug accumulation in lungs and blood after intratracheal administration of the spray dried inhalable hydrogel microparticles in comparison to orally administered Viagra®. The results demonstrated that formulated microparticles had a mean geometric particle size between 2 and 5 µm, entrapment efficiency of >80%, and yield ranging between 47 and 66% w/w. The in-vitro drug release profiles showed a sustained drug release of sildenafil citrate for over 24 h. The statistical design showed a significant influence of the microparticulate composition on the physicochemical properties. Furthermore, selected formulations were evaluated for their aerodynamic properties. The aerodynamic properties included fine particle fraction ranging between 24 and 30%, dose recovery percent of 68-8 5%, and average mass median aerodynamic diameter of 4.6-4.8 µm. The in-vivo pharmacokinetic study showed that inhaled spray dried hydrogel microparticles (M6) formulation had significantly higher lung/blood Cmax, AUC, extended half-life, and mean residence time in comparison to orally administered sildenafil citrate of the same dose. In conclusion, the formulated drug-loaded spray dried hydrogel microparticles showed promising in-vitro and in-vivo results for the pulmonary delivery of sildenafil citrate. The spray dried hydrogel microparticles formulation can be considered as a potential alternative of oral sildenafil citrate for treatment of PAH.