Exploration on the drug solubility enhancement in aqueous medium with the help of endo-functionalized molecular tubes: a computational approach.

One major problem in the pharmaceutical industry is the aqueous solubility of newly developed orally administered drug candidates. More than 50% of newly developed drug molecules suffer from low aqueous solubility. The therapeutic effects of drug molecules are majorly dependent on the bioavailability and, in essence, on the solubility of the used drug molecules. Thus, enhancement of drug solubility of sparingly soluble drug molecules is a need of modern times. Considering the high importance of drug solubility, we have computationally shown the enhancement of drug solubility for seven class II (poorly water-soluble) drug molecules in a water medium. The uses of supramolecular macrocycles have immense importance in the same field. Thus, we have used two synthetic supramolecular receptors named host-1a and host-1b to enhance the water solubility of fluorouracil, albendazole, camptothecin, clopidogrel, indomethacin, melphalan, and tolfenamic acid drug molecules. Biomedical engagements of a supramolecular receptor commence with the formation of stable host-drug complexes. These complexations enhance the water solubility of drug molecules and sustain the release rate and bioavailability of drug molecules. Thus, in this work, we focus on the formation of stable host-drug complexes in water medium. Molecular dynamics simulation is applied to analyze the structural features and the energetics involved in the host-drug complexation process. The information obtained at the atomistic level helps us gain better insights into the key interactions that operate to produce such highly stable complexes. Thus, we can propose that these two supramolecular receptors may be used as drug solubilizing agents, and patients will benefit from this theragnostic application shortly.

Selective Oxidation of Clopidogrel by Peroxymonosulfate (PMS) and Sodium Halide (NaX) System: An NMR Study.

A selective transformation of clopidogrel hydrogen sulfate (CLP) by reactive halogen species (HOX) generated from peroxymonosulfate (PMS) and sodium halide (NaX) is described. Other sustainable oxidants as well as different solvents have also been investigated. As result of this study, for each sodium salt the reaction conditions were optimized, and four different degradation products were formed. Three products were halogenated at C-2 on the thiophene ring and have concomitant functional transformation, such as N-oxide in the piperidine group. A halogenated endo-iminium product was also observed. With this condition, a fast preparation of known endo-iminium clopidogrel impurity (new counterion) was reported as well. The progress of the reaction was monitored using nuclear magnetic resonance spectroscopy as an analytical tool and all the products were characterized by 1D-, 2D-NMR and HRMS.

Evaluation of the effect of carrier material on modification of release characteristics of poor water soluble drug from liquisolid compacts.

Liquisolid compact is a novel dosage form in which a liquid medication (liquid drug, drug solution/dispersion in non-volatile solvent/solvent system) is converted to a dry, free flowing powder and compressed. Objective of the study was to elucidate the effect of carrier material on release characteristics of clopidogrel from liquisolid compacts. Different formulations of liquisolid compacts were developed using microcrystalline cellulose, starch maize, polyvinyl pyrollidone and hydroxypropyl methylcellulose as carrier material in three concentrations (40, 30 and 20%, w/w). Liquid vehicle was selected on the basis of solubility of clopidogrel. Colloidal silicondioxide was used as coating material and ratio of carrier to coating material was kept 10. A control formulation comprised of microcrystalline cellulose (diluents), tabletose-80 (diluents), primojel (disintegrant) and magnesium stearate (lubricant) was prepared by direct compression technique and was used for comparison. All the formulations were evaluated at pre and post compression level. Acid solubility profile showed higher solubility in HCl buffer pH2 (296.89±3.49 µg/mL). Mixture of propylene glycol and water (2:1, v/v) was selected as liquid vehicle. Drug content was in the range of 99-101% of the claimed quantity. All the formulations showed better mechanical strength and their friability was within the official limits (<1%). Microcrystalline cellulose and starch maize resulted in faster drug release while polyvinyl pyrollidone and HPMC resulted in sustaining drug release by gel formation. It is concluded from results that both fast release and sustained release of clopidogrel can be achieved by proper selection of carrier material.

Homochiral Covalent Organic Framework for Catalytic Asymmetric Synthesis of a Drug Intermediate.

(S)-2-(2-Chlorophenyl)-2-(6,7-dihydrothieno[3,2-c]pyridin-5(4H)-yl)acetonitrile ((S)-CIK) is a key intermediate in the synthesis of (S)-clopidogrel, which is one of the most saleable worldwide antiplatelet and antithrombotic drugs. We show herein a facile method for the direct synthesis of (S)-CIK via Strecker reaction using a homochiral covalent framework catalyst in a heterogeneous way. The asymmetric synthesis involves a photothermal-conversion-triggered, thermally driven reaction which affords (S)-CIK in 98% yield with 94% enantiomeric excess under visible-light irradiation. Furthermore, the above approach is readily extended to a gram-scale level on a fixed-bed continuous-flow model reactor. The potential utility of this strategy is highlighted by the preparation of many more other types of chiral drugs and drug intermediates in a green and facile way.

Stability of Azathioprine, Clonidine Hydrochloride, Clopidogrel Bisulfate, Ethambutol Hydrochloride, Griseofulvin, Hydralazine Hydrochloride, Nitrofurantoin, and Thioguanine Oral Suspensions Compounded with SyrSpend SF pH4.

To allow for tailored dosing and overcome swallowing difficulties, compounded liquid medication is often required in pediatric patients. The objective of this study was to evaluate the stability of oral suspensions compounded with SyrSpend SF PH4 and the commonly used active pharmaceutical ingredients azathioprine (powder) 50 mg/mL, azathioprine (from tablets) 50 mg/mL, clonidine hydrochloride (powder) 0.1 mg/mL, clopidogrel bisulfate (from tablets) 5 mg/mL, ethambutol hydrochloride (powder) 50 mg/mL, ethambutol hydrochloride (from tablets) 50 mg/mL, ethambutol hydrochloride (powder) 100 mg/mL, griseofulvin (powder) 25 mg/mL, hydralazine hydrochloride (powder) 4 mg/mL, nitrofurantoin (powder) 10 mg/mL, and thioguanine (powder) 2.5 mg/mL. Suspensions were compounded at the concentrations listed above and stored at controlled room and refrigerated temperatures. Stability was assessed by measuring the percentage recovery at 0 day (baseline), and at 7 days, 14 days, 30 days, 60 days, and 90 days. Active pharmaceutical ingredients quantification was performed by high-performance liquid chromatography, via a stability-indicating method. The following oral suspensions compounded using SyrSpend SF PH4 as the vehicle showed a beyond-use date of 90 days when stored both at room or refrigerated temperatures: clonidine hydrochloride 0.1 mg/mL, ethambutol hydrochloride 50 mg/mL and 100 mg/mL, griseofulvin 25 mg/mL, nitrofurantoin 10 mg/mL, and thioguanine 2.5 mg/mL, all compounded from the active pharmaceutical ingredients in powder form. Suspensions compounded using the active pharmaceutical ingredients from tablets presented a lower beyond-use date: 30 days for ethambutol hydrochloride 50 mg/mL and hydralazine hydrochloride 4 mg/mL, stored at both temperatures, and for clopidogrel bisulfate 5 mg/mL when stored only at refrigerated temperature. Azathioprine suspensions showed a beyond-use date of 14 days when compounded using active pharmaceutical ingredients in powder form at both temperatures. This suggests that SyrSpend SF PH4 is suitable for compounding active pharmaceutical ingredients from different pharmacological classes.

Freeze-Dried Clopidogrel Loaded Lyotropic Liquid Crystal: Box-Behnken Optimization, In-Vitro and In-Vivo Evaluation.

BACKGROUND: Clopidogrel (CLP) suffers from extensive first pass metabolism results in a negative impact on its oral systemic bioavailability. Cubosomes are Lyotropic Liquid Crystalline (LLC) nano-systems comprising monoolein, a steric stabilizer and an aqueous system, it considered a promising carrier for different pharmaceutical compounds. Box-Behnken Design (BBD) is an efficient tool for process analysis and optimization skipping forceful treatment combinations. OBJECTIVE: The study was designed to develop freeze-dried clopidogrel loaded LLC (cubosomes) for enhancement of its oral bioavailability. METHODS: A 33 BBD was adopted, the studied independent factors were glyceryl monooleate (GMO lipid phase), Pluronic F127 (PL F127steric stabilizer) and polyvinyl alcohol powder (stabilizer). Particle Size (PS), Polydispersity Index (PDI) and Zeta Potential (ZP) were set as independent response variables. Seventeen formulae were prepared in accordance with the bottom up approach and in-vitro evaluated regarding PS, PDI and ZP. Statistical analysis and optimization were achieved using design expert software®, then the optimum suggested formula was prepared, in-vitro revaluated, freeze-dried with 3% mannitol (cryoprotectant), solid state characterized and finally packed in hard gelatin capsule for comparative in-vitro release and in-vivo evaluation to Plavix®. RESULTS: Results of statistical analysis of each individual response revealed a quadratic model for PS and PDI where a linear model for ZP. The optimum suggested formula with desirability factor equal 0.990 consisting of (200 mg GMO, 78.15 mg PL F127 and 2% PVA). LC/MS/MS study confirmed significant higher Cmax, AUC0-24h and AUC0-∞ than that of Plavix®. CONCLUSION: The results confirm the capability of developed carrier to overcome the low oral bioavailability.

DT-678 inhibits platelet activation with lower tendency for bleeding compared to existing P2Y12 antagonists.

The novel clopidogrel conjugate, DT-678, is an effective inhibitor of platelets and thrombosis in preclinical studies. However, a comparison of the bleeding risk with DT-678 and currently approved P2Y12 antagonists has yet to be determined. The objective of this study was to evaluate the bleeding tendency of animals treated with clopidogrel, ticagrelor, and DT-678. Ninety-one New Zealand white rabbits were randomized to one of 13 treatment groups (n = 7). Platelet activation was assessed by flow cytometry and light transmission aggregometry before and after the administration of various doses of DT-678, clopidogrel, and ticagrelor. Tongue template bleeding times were also measured before and after drug treatment. Treatment with P2Y12 receptor antagonists caused a dose-dependent reduction in markers of platelet activation (P-selectin and integrin αIIbß3) and aggregation in response to adenosine diphosphate stimulation. At the same doses required for platelet inhibition, clopidogrel and ticagrelor significantly prolonged bleeding times, while DT-678 did not. DT-678 and the FDA-approved P2Y12 antagonists clopidogrel and ticagrelor are effective inhibitors of platelet activation and aggregation. However, unlike clopidogrel and ticagrelor, DT-678 did not prolong bleeding times at equally effective antiplatelet doses. The results suggest a more favorable benefit/risk ratio for DT-678 and potential utility as part of a dual antiplatelet therapy regimen.

Box-Behnken design directed optimization for sensitivity assessment of anti-platelet drugs.

Optimization of electrospray ionization (ESI) parameters is routinely carried out by one factor at a time (OFAT) or auto-tune software (ATS). Design of experiments (DOE) approach has been reported to be an excellent alternative to OFAT or ATS. Box-Behnken Design (BBD) was successfully used to optimize ESI parameters like nebulizing gas flow rate, desolvation line temperature, heat block temperature, and drying gas flow rate for [M + H]+ intensity of Clopidogrel bisulfate (CLP) and Ticlopidine (TLP). BBD model was found to be significant with p < .0001 for both CLP and TLP. The predicted and optimized (OL) ESI parameters were used for chromatographic analysis and were compared against three levels of ESI parameters, i.e. low level (LL), medium level (ML), and high level (HL). The OL ESI parameters were subjected to chromatographic analysis and its mean peak area was significantly higher than mean peak area for LL, ML, and HL ESI in case of CLP and TLP (p < .001). However, no significant difference was observed between the mean peak area for ML and OL of TLP. Thus, BBD can be considered with 29 trials to optimize four mass spectrometric parameters. The liquid chromatographic parameters percentage of methanol, percentage of formic acid and flow rate were also optimized using BBD. However, the optimized method did not significantly influence the peak response over the non-optimized method.

Stabilizing excipients for engineered clopidogrel bisulfate procubosome derived in situ cubosomes for enhanced intestinal dissolution: Stability and bioavailability considerations.

Clopidogrel bisulfate (CB) is a golden antiplatelet treatment, yet its benefits are limited by its low bioavailability (<50%) caused by poor intestinal solubility and absorption. The present study aims to improve CB intestinal solubility and absorption through developing a novel stable dry CB procubosomes tablets ready to disintegrate and re-disperse upon dilution in the GIT forming in situ CB cubosome nanoparticles while simultaneously overcome the poor stability of conventional cubosome dispersion at room temperature. Glyceryl monooleate based CB cubosome dispersion was prepared using Poloxamer 407 as surfactant, freeze dried using different stabilizing excipients (dextrose, mannitol and avicel) then compressed into procubosome tablets. The effect of excipient's physicochemical properties on the flowability, in vitro dissolution and stability at accelerated conditions (40 ±â€¯2 °C/75 ±â€¯5% RH) were evaluated. The prepared procubosomes exhibited an excipient type dependent dissolution profile where Avicel based procubosome tablet CF2 showed the highest in vitro dissolution profile among other excipients used during the freeze drying process. Upon transition to intestinal pH of 6.8 to mimic the drug absorption site, CF2 procubosome Avicel tablet, was able to preserve the enhanced CB release profile (99.6 ±â€¯6.92%) compared to commercial Plavix® where, CB dissolved % dropped dramatically to 79.1 ±â€¯2.45%. After storage for six months, CF2 retained the fresh tablet drug content of 98.5 ±â€¯5.82% and dissolution properties. Moreover, following oral administration in rabbits, CF2 showed higher relative bioavailability (153%) compared to commercial Plavix® with significant higher Cmax,shorter tmax, as well as enhanced antiplatelet activity.

Probing the effect of various lipids and polymer blends on clopidogrel encapsulated floating microcarriers.

BACKGROUND: Clopidogrel (CLOP) is an antiplatelet drug with poor solubility in intestinal fluid, which limits its bioavailability after oral administration. OBJECTIVES: Current study focuses on developing site-specific floating microcarriers of CLOP using solvent diffusion evaporation method (SDEM) for retaining the drug in the stomach, thus improving the solubility of drug for better absorption. METHODS: SDEM was employed to formulate floating microcarriers using lipidic excipients, namely Gelucires (GL) to impart floating properties, in combination with ethyl cellulose as release retarding polymer. RESULTS: Prepared particles were 169 ± 6 µm to 375 ± 13 µm in size, whilst encapsulation efficiency was ranged from 39.6 ± 0.60% to 96.50 ± 3.50%. Electron micrographs depicted discrete spherical microcarriers with porous structure, which amplified with increasing HLB value of GL and concentration of Eudragit E100. FTIR study confirmed absence of major drug polymer interactions while DSC and XRD studies revealed the presence of non-crystalline nature of drug in all formulations. Drug release at pH 1.2 enhanced more than 2-folds with increasing HLB value with 32% cumulative drug release for GL 43/01 and 69% for GL 50/13. More interestingly, adding various proportions of Eudragit E100 to GL 43/01 based formulations resulted in increased drug release as high as 71%. In all formulations, the drug release followed diffusion dependent process. CONCLUSION: It is envisaged that this formulation strategy for CLOP is promising and could possibly be tested in future for its in vivo performance. Graphical abstract Lipid based floating microcarriers of clopidogrel.

Comparison of Active Substance Losses and Total Weight Losses of Tablets Administered Via Feeding Tube.

BACKGROUND/AIMS: Administration of tablets via feeding tube (FT) is often associated with significant drug losses, as was confirmed by weighing. The aim of this study was to measure the proportion of active substance losses (ASLs) in an in vitro model. METHODS: A film-coated tablet (FilmCT) containing clopidogrel (Trombex®) and a tablet with enteric coating (EntericCT) containing pantoprazole (Controloc®) were crushed in a mortar and transferred by method A (tablet powder was transferred into the beaker, poured into the syringe and water added) and method B (water was added into the mortar, suspension drawn into the syringe) and administered via FT in an in vitro model. Total losses were measured with analytical balance and, simultaneously, ASL were analyzed with high-performance liquid chromatography UV-detection (HPLC-UV). RESULTS: ASL was different to weighing only in the case of EntericCT prepared by method B (2.0 ± 4.2 and 10.7 ± 0.8% for HPLC-UV and weighing, respectively; p = 0.004). HPLC-UV confirmed significantly lower ASL when method B was used for either EntericCT (34.3 ± 7.2 vs. 2.0 ± 4.2%; p < 0.001) or FilmCT (14.1 ± 2.2 vs. 7.7 ± 4.1%; p < 0.01). CONCLUSION: Drug loss analysis with analytical balance may overestimate ASL, as was proved for EntericCT in this study. ASL were significantly lower when method B was used.

Development of stability-indicating HPLC method and accelerated stability studies for osmotic and pulsatile tablet formulations of Clopidogrel Bisulfate.

The purpose of the present study is to develop a simple, rapid and sensitive stability-indicating high-performance liquid chromatography (HPLC) method for Clopidogrel Bisulfate (CBS) and further extending it for assessment of CBS stability in osmotic and pulsatile tablet formulations tested under accelerated conditions. A stability-indicating HPLC method for quantitative determination of CBS in gastro-retentive formulations is developed by using a C18 HPLC column, acetonitrile and 0.1% formic acid (60:40 v/v) as mobile phase, with a flow rate of 0.9 mL/min, UV detection at 222 nm and subsequently validated. The key objective was to analyze the stability profile of formulations under accelerated conditions. The retention time (Rt) of CBS was observed as 5.9 min with the linearity range between 0.06-1.95 µg/mL. Forced degradation studies were performed on bulk samples of CBS using acidic, basic, oxidative, thermal (80 °C) and photolytic (under sunlight) conditions. The resulting method was validated as per ICH Q2(R1) guidelines. Moreover, an attempt has been made to identify the degradation products by Liquid chromatography-mass spectrometry (LC-MS) analysis. The proposed method was successfully applied to novel gastro-retentive tablet formulations (osmotic tablet and pulsatile tablet) for assessment of stability under accelerated conditions.

Electrolysis promoted reductive amination of electron-deficient aldehydes/ketones: a green route to the racemic clopidogrel.

An electrocatalytic reductive amination of electron-deficient aldehydes/ketones was developed, which could be used in the synthesis of functionalized tertiary amines and large scale preparation of racemic clopidogrel. A plausible mechanism involving an iminium cation intermediate was proposed.

Clopidogrel as a donor probe and thioenol derivatives as flexible promoieties for enabling H2S biomedicine.

Hydrogen sulfide has emerged as a critical endogenous signaling transmitter and a potentially versatile therapeutic agent. The key challenges in this field include the lack of approved hydrogen sulfide-releasing probes for in human exploration and the lack of controllable hydrogen sulfide promoieties that can be flexibly installed for therapeutics development. Here we report the identification of the widely used antithrombotic drug clopidogrel as a clinical hydrogen sulfide donor. Clopidogrel is metabolized in patients to form a circulating metabolite that contains a thioenol substructure, which is found to undergo spontaneous degradation to release hydrogen sulfide. Model studies demonstrate that thioenol derivatives are a class of controllable promoieties that can be conveniently installed on a minimal structure of ketone with an α-hydrogen. These results can provide chemical tools for advancing hydrogen sulfide biomedical research as well as developing hydrogen sulfide-releasing drugs.

Interaction study between antiplatelet agents, anticoagulants, thyroid replacement therapy and a bioavailable formulation of curcumin (Meriva®).

OBJECTIVE: The objective of this clinical study is to evaluate possible interactions between antiplatelet agents, anticoagulants, thyroid hormone replacement therapy and a formulation of curcumin (Meriva®) that resulted effective for the complementary treatment of osteoarthritis. PATIENTS AND METHODS: Interaction between antiplatelet agents and Meriva® was evaluated by measuring anti-platelet activity with the in-vivo bleeding-time (BT) in patients assuming acetylsalicylic acid or ticlopidine or clopidogrel from at least 2 years. The BT was evaluated before and after 10 days of supplementation with Meriva®. The interaction between anticoagulants and Meriva® was evaluated in patients using warfarin or dabigatran for previous venous thrombosis. The INR level was evaluated before and after 10 days of supplementation with the curcumin formulation. Thyroid function tests in hypothyroid patients using LT4 replacement therapy (Eutirox®) were evaluated before and after 15 days of supplementation with Meriva®. Similarly, levels of glycemia and glycated hemoglobin were evaluated in diabetic patients in treatment with metformin, before and after 10 days of supplementation with the studied product. RESULTS: After 10 days of supplementation with Meriva® the average BT value was not significantly different for patients assuming acetylsalicylic acid, ticlopidine or clopidogrel at standard dosages. Similarly, after 10 days of Meriva® treatment, the INR level in the two groups of patients assuming warfarin or dabigatran was not statistically different from that observed at baseline. In the analyzed patients assuming LT4 or metformin, no interactions between the therapy and Meriva® were observed. CONCLUSIONS: Results from this non-interaction clinical study suggest that Meriva® does not interfere with the antiplatelet activity of the most common antiplatelet agents nor alters the INR values in stable patients assuming warfarin or dabigatran. Similarly, dosages of LT4 or metformin do not need to be adjusted in case of complementary treatment with Meriva®.

Comparative Oral Drug Classification Systems: Acetazolamide, Azithromycin, Clopidogrel, and Efavirenz Case Studies.

Biopharmaceutics classification systems based on the properties of solubility and permeability or the extension of metabolism are very important tools in the early stages of the development and regulatory stages of new products. However, until now, there was no clear understanding between the interplay among these classification systems. Therefore, the main objective of this work was to make a comparison of concepts of BCS and BDDCS to understand what are the key factors that allow for the integration of these biopharmaceutics classification systems. Also, the suitability of an in situ single-pass intestinal perfusion assay in rats (SPIP) development was assessed by us to determine the limit between high and low permeability following what the FDA BCS guidance suggests. An excellent correlation was found between the values of permeability obtained by applying SPIP assays and the extensions of the metabolism of the set of compounds studied in this work, with the exception of three compounds that showed disparity between their permeability coefficients ( Peff), obtained herein by SPIP, and their metabolism (acetazolamide, azithromycin, and efavirenz). Discrepancies allowed us to elucidate the interrelationship between BCS and BDDCS.