Synthesis and in vitro/in vivo evaluation of novel oral N-alkyl- and N,N-dialkyl-carbamate esters of entacapone

Entacapone has a relatively low oral bioavailability which may, in part, be due to its low aqueous solubility at low pH and/or its hydrophilic character at neutral pH. Various novel N-alkyl and N,N-dialkyl carbamate esters of entacapone were synthesized as possible prodrugs of entacapone in order to increase its aqueous solubility at an acidic pH and to increase its lipophilicity at neutral pH. Oral bioavailability of entacapone and selected carbamate esters were investigated in rats. Both N-alkyl and N,N-dialkyl carbamate esters were relatively stable against chemical hydrolysis at pH 7.4 (t1/2 = 14.9-20.7 h), but hydrolyzed rapidly (t1/2 = 0.8-2.7 h) in human serum. However, in contrast to N-alkyl carbamates, N,N-dialkyl carbamates did not release entacapone in in vitro enzymatic hydrolysis (human serum) studies. N-Alkyl carbamates, 2a-c, showed increased aqueous solubility at pH 7.4, of which 2a and 2c also show increased aqueous solubility at pH 5.0, compared to entacapone. In addition to increased aqueous solubility, 2c showed increased lipophilicity at pH 7.4. However, two N-alkyl carbamates of entacapone did not increase the oral bioavailability of the parent drug in rats. Thus, it can be concluded that the relatively low lipophilicity of entacapone is not the cause of its low bioavailability.     

Oral formulation of a novel antiviral agent,PG301029, in a mixture of Gelucire 44/14 and DMA (2∶1, wt/wt)

To develop an oral formulation for PG301029, a novel potent agent for the treatment of Hepatitis C virus infection, that not only has very low aqueous solubility but also degrades rapidly in water. The solubility of PG301029 was determined in water, various aqueous media, and several neat organic solvents. The stability of PG301029 was monitored at room temperature in buffess for 4 days, and in several neat organic solvents for up to 8 mo. Drug concentrations were measured by high-performance liquid chromatography (HPLC). Based on solubility and stability data, Gelucire 44/14 and DMA (N,N-dimethylacetamide) at a weight ratio of 2 to 1 were chosen as the formulation vehicle. After the vehicle was prepared, it was maintained in liquid form at ∼40°C until the PG301029 was dissolved. The final formulation product was a semisolid at room temperature. The bioavailability of the formulation was tested on 4 female BALB/c mice. PG301029 is insoluble in all tested aqueous media, while its solubility is promising in DMA. This compound is unstable in aqueous media and some organic solvents; however, it is stable in DMA. This proposed formulation is able to hold up to 10 mg/mL of drug and is stable at 4°C. The shelf life for this formulation stored at 4°C is extrapolated to be greater than 4 years. This formulation dramatically increases the bioavailability of PG301029. This nonaqueous formulation solves the stability, solubility, and bioavailability problems for PG301029. This semisolid formulation can easily be incorporated into soft elastic capsules.     

Elevating bioavailability of cyclosporine a via encapsulation in artificial oil bodies stabilized by caleosin

To elevate its bioavailability via oral administration, cyclosporine A (CsA), a hydrophobic drug, was either incorporated into olive oil directly or encapsulated in artificial oil bodies (AOBs) constituted with olive oil and phospholipid in the presence or absence of recombinant caleosin purified from Escherichia coli. The bioavailabilities of CsA in these formulations were assessed in Wistar rats in comparison with the commercial formulation, Sandimmun Neoral. Among these tests, CsA-loaded AOBs stabilized by the recombinant caleosin exhibited better bioavailability than the commercial formulation and possessed the highest maximum whole blood concentration (C(max)), 1247.4 +/- 106.8 ng/mL, in the experimental animals 4.3 +/- 0.7 h (t(max)) after oral administration. C(max) and the area under the plasma concentration-time curve (AUC(0-24)) were individually increased by 50.8% and 71.3% in the rats fed with caleosin-stabilized AOBs when compared with those fed with the reference Sandimmun Neoral. The results suggest that constitution of AOBs stabilized by caleosin may be a suitable technique to encapsulate hydrophobic drugs for oral administration.     

Highly sensitive determination of saquinavir in biological samples using liquid chromatography-tandem mass spectrometry

A selective and sensitive method for the determination of the HIV protease inhibitor saquinavir in human plasma, saliva, and urine using liquid-liquid extraction and LC-MS-MS has been developed, validated, and applied to samples of a healthy individual. After extraction with ethyl acetate, sample extracts were chromatographed isocratically within 5 min on Kromasil RP-18. The drug was detected with tandem mass spectrometry in the selected reaction monitoring mode using an electrospray ion source and 2H(5)-saquinavir as internal standard. The limit of quantification was 0.05 ng/mL. The accuracy of the method varied between -1 and +10% (SD within-batch) and the precision ranged from +4 to +10% (SD batch-to-batch). The method is linear at least within 0.05 and 87.6 ng/mL. After a regular oral dose (600 mg) saquinavir concentrations were detectable for 48 h in plasma and were well correlated with saliva concentrations (r(2)=0.9348, mean saliva/plasma ratio 1:15.1). The method is well suited for low saquinavir concentrations in different matrices.     

Oral Bioavailability Enhancement of Exemestane from Self-Microemulsifying Drug Delivery System (SMEDDS)

Limited aqueous solubility of exemestane leads to high variability in absorption after oral administration. To improve the solubility and bioavailability of exemestane, the self-microemulsifying drug delivery system (SMEDDS) was developed. SMEDDS comprises of isotropic mixture of natural or synthetic oil, surfactant, and cosurfactant, which, upon dilution with aqueous media, spontaneously form fine o/w microemulsion with less than 100 nm in droplet size. Solubility of exemestane were determined in various vehicles. Ternary phase diagrams were plotted to identify the efficient self-emulsification region. Dilution studies, droplet size, and zeta potential of the formulations were investigated. The release of exemestane from SMEDDS capsules was studied using USP dissolution apparatus in different dissolution media and compared the release of exemestane from a conventional tablet. Oral pharmacokinetic study was performed in female Wistar rats (n = 8) at the dose of 30 mg kg⁻¹. The absorption of exemestane from SMEDDS form resulted in about 2.9-fold increase in bioavailability compared with the suspension. Our studies illustrated the potential use of SMEDDS for the delivery of hydrophobic compounds, such as exemestane by the oral route.Key words: bioavailability enhancement, exemestane, microemulsion, SMEDDS     

Novel Self-Nanoemulsifying Drug Delivery Systems (SNEDDS) for Oral Delivery of Cinnarizine: Design, Optimization, and In-Vitro Assessment

Due to its extreme lipophilicity, the oral delivery of cinnarizine (CN) encounters several problems such as poor aqueous solubility and pH-dependent dissolution, which result in low and erratic bioavailability. The current study aims to design self-nanoemulsifying drug delivery systems (SNEDDS) of CN that circumvent such obstacles. Equilibrium solubility of CN was determined in a range of anhydrous and diluted lipid-based formulations. Dynamic dispersion tests were carried out to investigate the efficiency of drug release and magnitude of precipitation that could occur upon aqueous dilution. Droplet sizes of selected formulations, upon (1:1,000) aqueous dilution, were presented. The optimal formulations were enrolled in subsequent dissolution studies. The results showed that increasing lipid chain length and surfactant lipophilicity raised the formulation solvent capacity, while adding co-solvents provoked a negative influence. The inclusion of mixed glycerides and/or hydrophilic surfactants improved the drug release efficiency. Generally, no significant precipitation was observed upon aqueous dilution of the formulations. Five formulations were optimal in terms of their superior self-emulsifying efficiency, drug solubility, dispersion characteristics, and lower droplet size. Furthermore, the optimal formulations showed superior dissolution profile compared to the marketed (Stugeron®) tablet. Most importantly, they could resist the intensive precipitation observed with the marketed tablet upon shifting from acidic to alkaline media. However, SNEDDS containing medium-chain mixed glycerides showed the highest drug release rate and provide great potential to enhance the oral CN delivery. Accordingly, the lipid portion seems to be the most vital component in designing CN self-nanoemulsifying systems.     

Absorption and enterohepatic circulation of baicalin in rats

Pharmacokinetics of baicalin, in form of its parent drug (BG) and conjugated metabolites (BGM), were studied following intravenous and oral administration of baicalin to intact rats. The enterohepatic circulation of BG and BGM was also assessed in a linked-rat model. Multiple plasma and urine samples were collected, and concentrations of BG and BGM were determined using a liquid chromatography/tandem mass spectrometry method. The concentration of BGM was assayed in the form of baicalein after treatment with beta-glucuronidase/sulfatase. After i.v. administration, plasma concentration of BG rapidly declined with the elimination half-life (T1/2) of 0.1 till 4 h post dose, followed by slight increase from 4-8 h in plasma concentrations after drug administration. These plasma concentrations resulted in a significant prolongation of the terminal elimination half-life of BG (T1/2 TER, 9.7 h). BG also displayed slight increase in plasma concentrations (12-24 h) after oral administration, with T1/2 TER of 12.1 h. Based on the AUC of BG and BGM, the absolute bioavailability of baicalin was 2.2+/-0.2% and 27.8+/-5.6%, respectively. The exposure of baicalin to the systemic circulation was approximately 118-fold lower than that of BGM after oral administration (AUC0-t, 4.43 versus 523.97 nmol.h/mL). The high extent of glucuronidation suggested the possible presence of enterohepatic circulation, which was confirmed in the linked-rat model since plasma concentrations of BG and BGM were observed in bile-recipient rats at 4 to 36 h. The extent of enterohepatic circulation after intravenous administration of baicalin was 4.8% and 13.3% for BG and BGM, respectively. It was determined that 18.7% and 19.3% of the administered baicalin were subjected to enterohepatic circulation for BG and BGM, respectively, after oral administration. These results confirm that BG undergoes extensive first-pass glucuronidation and that enterohepatic circulation contributes significantly to the exposure of BG and BGM in rats.     

Improved Oral Bioavalability of Mebudipine Upon Administration in PhytoSolve and Phosal-Based Formulation (PBF)

The aim of this investigation was to examine the efficacy of PhytoSolve and Phosal-based formulation (PBF) to enhance the oral bioavailability of mebudipine, which is a poorly water-soluble calcium channel blocker. The solubility of mebudipine in various oils was determined. PhytoSolve was prepared with a medium-chain triglyceride (MCT) oil (20%), soybean phospholipids (5%), and a 70% fructose solution (75%). The influence of the weight ratio of Phosal 50PG to glycerol in PBF on the mean globule size was studied with dynamic light scattering. The optimized formulation was evaluated for robustness toward dilution, transparency, droplet size, and zeta potential. The in vivo oral absorption of different mebudipine formulations (PhytoSolve, PBF, oily solution, and suspension) were evaluated in rats. The optimized PBF contained Phosal 50PG/glycerol in a 6:4 ratio (w/w). The PBF and PhytoSolve formulations were miscible with water in any ratio and did not demonstrate any phase separation or drug precipitation over 1 month of storage. The mean particle size of PhytoSolve and PBF were 138.5 ± 9.0 and 74.4 ± 2.5 nm, respectively. The in vivo study demonstrated that the oral bioavailability of PhytoSolve and PBF in rats was significantly higher than that of the other formulations. The PhytoSolve and PBF formulations of mebudipine are found to be more bioavailable compared with suspension and oily solutions during an in vivo study in rats. These formulations might be new alternative carriers that increase the oral bioavailability of poorly water-soluble molecules, such as mebudipine.KEY WORDS: mebudipine, oral bioavailability, Phosal 50PG, PhytoSolve     

Ultra Rapidly Dissolving Repaglinide Nanosized Crystals Prepared via Bottom-Up and Top-Down Approach: Influence of Food on Pharmacokinetics Behavior

The present work was undertaken with the objectives of improving the dissolution velocity, related oral bioavailability, and minimizing the fasted/fed state variability of repaglinide, a poorly water-soluble anti-diabetic active by exploring the principles of nanotechnology. Nanocrystal formulations were prepared by both top-down and bottom-up approaches. These approaches were compared in light of their ability to provide the formulation stability in terms of particle size. Soluplus® was used as a stabilizer and Kolliphor™ E-TPGS was used as an oral absorption enhancer. In vitro dissolution profiles were investigated in distilled water, fasted and fed state simulated gastric fluid, and compared with the pure repaglinide. In vivo pharmacokinetics was performed in both the fasted and fed state using Wistar rats. Oral hypoglycemic activity was also assessed in streptozotocin-induced diabetic rats. Nanocrystals TD-A and TD-B showed 19.86 and 25.67-fold increase in saturation solubility, respectively, when compared with pure repaglinide. Almost 10 (TD-A) and 15 (TD-B)-fold enhancement in the oral bioavailability of nanocrystals was observed regardless of the fasted/fed state compared to pure repaglinide. Nanocrystal formulations also demonstrated significant (p < 0.001) hypoglycemic activity with faster onset (less than 30 min) and prolonged duration (up to 8 h) compared to pure repaglinide (after 60 min; up to 4 h, respectively).KEY WORDS: diabetes mellitus, fasted and fed state variability, nanocrystal, oral hypoglycemic activity, repaglinide     

Prodrugs of 3-(3,4-dichlorobenzyloxy)-2-amino-6-fluorobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (MGS0039): a potent and orally active group II mGluR antagonist with antidepressant-like potential

3-(3,4-Dichlorobenzyloxy)-2-amino-6-fluorobicyclo[3.1.0]hexane-2,6-dicarboxylic acid 5 (MGS0039) is a highly selective and potent group II metabotropic glutamate receptor (mGluR) antagonist (antagonist activities for mGluR2; IC50=20.0 nM, mGluR3; IC50=24.0 nM) and is detected in both plasma (492 ng/mL) and brain (13.2 ng/g) at oral administration of 10 ng/mL [J. Med. Chem.2004, 47, 4750], but the oral bioavailability of 5 was 10.9%. In order to improve the oral bioavailability of 5, prodrugs of 5 were discovered by esterification of carboxyl group on C6-position of bicyclo[3.1.0]hexane ring. Among these compounds, 6-alkyl esters exhibited approximately 10-fold higher concentrations of 5 in the plasma and brain of rats after oral administration (e.g., ethyl ester of 5; plasma, Cmax=20.7+/-1.3 microM) compared to oral administration of 5 (plasma, Cmax=2.46+/-0.62 microM). 3-(3,4-Dichlorobenzyloxy)-2-amino-6-fluorobicyclo[3.1.0]hexane-2,6-dicarboxylic acid 6-heptyl ester (7ao), a prodrug of MGS0039, showed antidepressant-like effects in rat forced swimming test and mouse tail suspension test following oral administration. Moreover, following oral administration of 7ao in mice, high concentrations of MGS0039 were detected in both the brain and plasma, while 7ao was barely detected. In this paper, we report the synthesis, in vitro metabolic stabilities, and pharmacokinetic profiles of the prodrugs of 5, and the antidepressant-like effects of 7ao.     

Oral fast-dissolving films containing lutein nanocrystals for improved bioavailability: formulation development, <Emphasis Type="Italic">in vitro</Emphasis> and <Emphasis Type="Italic">in vivo</Emphasis> evaluation

Lutein is widely used as diet supplement for prevention of age-related macular degeneration. However, the application and efficacy of lutein in food and nutritional products has been hampered due to its poor solubility and low oral bioavailability. This study aimed to develop and evaluate the formulation of oral fast-dissolving film (OFDF) containing lutein nanocrystals for enhanced bioavailability and compliance. Lutein nanocrystals were prepared by anti-solvent precipitation method and then encapsulated into the films by solvent casting method. The formulation of OFDF was optimized by Box-Behnken Design (BBD) as follows: HPMC 2.05% (w/v), PEG 400 1.03% (w/v), Cremophor EL 0.43% (w/v). The obtained films exhibited uniform thickness of 35.64 ± 1.64 μm and drug content of 0.230 ± 0.003 mg/cm² and disintegrated rapidly in 29 ± 8 s. The nanocrystal-loaded films with reconstituted particle size of 377.9 nm showed better folding endurance and faster release rate in vitro than the conventional OFDFs with raw lutein. The microscope images, thermograms, and diffractograms indicated that lutein nanocrystals were highly dispersed into the films. After administrated to SD rats, t _max was decreased from 3 h for oral solution formulation to less than 0.8 h for OFDF formulations, and C _max increased from 150 ng/mL for solution to 350 ng/mL for conventional OFDF or 830 ng/mL for nanocrystal OFDF. The AUC _0-24h of conventional or nanocrystal OFDF was 1.37 or 2.08-fold higher than that of the oral solution, respectively. These results suggested that drug nanocrystal-loaded OFDF can be applied as a promising approach for enhanced bioavailability of poor soluble drugs like lutein.     

Preparation and Evaluation of Diosgenin Nanocrystals to Improve Oral Bioavailability

Diosgenin (DSG), a well-known steroid sapogenin derived from Dioscorea nipponica Makino and Dioscorea zingiberensis Wright, has a variety of bioactivities. However, it shows low oral bioavailability due to poor aqueous solubility and strong hydrophobicity. The present study aimed to develop DSG nanocrystals to increase the dissolution and then improve the oral bioavailability and biopharmaceutical properties of DSG. DSG nanocrystals were prepared by the media milling method using a combination of pluronic F127 and sodium dodecyl sulfate as surface stabilizers. The physicochemical properties of the optimal DSG nanocrystals were characterized using their particle size distribution, morphology, differential scanning calorimetry, powder X-ray diffraction, Fourier transform infrared spectroscopy data, and solubility and dissolution test results. Pharmacokinetic studies of the DSG coarse suspension and its nanocrystals were performed in rats. The particle size and polydispersity index of DSG nanocrystals were 229.0?±?3.7 nm and 0.163?±?0.064, respectively. DSG retained its original crystalline state during the manufacturing process, and its chemical structure was not compromised by the nanonizing process. The dissolution rate of the freeze-dried DSG nanocrystals was significantly improved in comparison with the original DSG. The pharmacokinetic studies showed that the AUC_0–72h and C _max of DSG nanocrystals increased markedly (p?<?0.01) in comparison with the DSG coarse suspension by about 2.55- and 2.01-fold, respectively. The use of optimized nanocrystals is a good and efficient strategy for oral administration of DSG due to the increased dissolution rate and oral bioavailability of DSG nanocrystals.     

Development and Evaluation of Avanafil Self-nanoemulsifying Drug Delivery System with Rapid Onset of Action and Enhanced Bioavailability

Utilization of lipid-based drug delivery systems has recently gained focus for drugs characterized by poor aqueous solubility. The improved aqueous solubility overcomes one of the main barriers that limit their bioavailability. The objective of this work was to improve the solubility and oral bioavailability of Avanafil (AVA), a recently approved second generation type 5 phospodiesterase inhibitor used for erectile dysfunction.AVA was formulated as self-nanoemulsifying drug delivery system (SNEDDS) utilizing various oils, surfactants, and cosurfactants. The solubility of AVA in various oils, surfactants, and cosurfactants was determined. Ternary phase diagram was constructed to identify stable nanoemulsion region. The prepared AVA loaded SNEDDS were assessed for optical clarity, droplet size, conductivity, and stability studies. In vitro drug release and in vivo pharmacokinetic parameters using animal model were also investigated. Results revealed that stable AVA (SNEDDS) were successfully developed with a droplet size range of 65 to 190 nm. SNEDDS composed of 25% dill oil, 55% Tween 80, and 20% propylene glycol successfully improved solubilization of AVA (over 80% within 30 min) vis-a-vis the powder AVA (35% within 30 min). In vivo pharmacokinetic showed a significant (P < 0.05) increase in C_max, reduction in T_max, and SNEDDS enhanced the bioavailability in the rats by 1.4-fold when compared with pure drug.Key words: avanafil, erectile dysfunction, dill oil, self-nanoemulsifying, SNEDDS     

Self-Assembling Raloxifene Loaded Mixed Micelles: Formulation Optimization, <Emphasis Type="Italic">In Vitro</Emphasis> Cytotoxicity and <Emphasis Type="Italic">In Vivo</Emphasis> Pharmacokinetics

Raloxifene (RLX) has been strongly recommended for postmenopausal women at high risk of invasive breast cancer and for prevention of osteoporosis. However, low aqueous solubility and reduced bioavailability hinder its clinical application. The objective of this study was to explore the potential of RLX loaded mixed micelles (RLX-MM) using Pluronic F68 and Gelucire 44/14 for enhanced bioavailability and improved anticancer activity on human breast cancer cell line (MCF-7). RLX-MM were prepared by solvent evaporation method and optimized using 3² factorial design. The average size, entrapment efficiency and zeta potential of the optimized formulation were found to be 190?±?3.3 nm, 79?±?1.3%, 13?±?0.8 mV, respectively. In vitro study demonstrated 74.68% drug release from RLX-MM in comparison to 42.49% drug release from RLX dispersion. According to the in vitro cytotoxicity assay, GI₅₀ values on MCF-7 breast cancer cell line for RLX-MM and free RLX were found to be 22.5 and 94.71 μg/mL, respectively. Significant improvement (P?<?0.05) in the anticancer activity on MCF-7 cell line was observed in RLX-MM over RLX pure drug. Additionally, oral bioavailability of RLX-MM was improved by 1.5-fold over free RLX when administered in female Wistar rats. Incorporation of RLX in the hydrophobic core and improved solubility of the drug due to hydrophilic shell attributed to the enhanced cytotoxicity and bioavailability of RLX-MM. This research establishes the potential of RLX loaded mixed micelles of Pluronic F68 and Gelucire 44/14 for improved bioavailability and anticancer activity on MCF-7 cell line.     

The rifampicin drug delivery system based on phospholipid nanoparticles

Low bioavailability of rifampicin, one of the main antituberculous agents, stimulates searches of its new optimized formulations. The present study has shown a possibility of rifampicin incorporation into nanoparticles from plant phosphatidylcholine (diameter of 20–30 nm). Addition of sodium oleate to the phospholipid system caused a 2-fold increase in the percent of rifampicin incorporation. The maximal concentration of rifampicin assayed in plasma samples by LC/MS was observed 1 h after oral administration to rats (6 mg/kg) and represented 0.5 and 4.2 μg/mL for free rifampicin and rifampicin incorporated in the phospholipids-oleate nanoparticles, respectively. These levels were maintained for more than 2 h of the experiment. High rifampicin bioavailability in the oleate containing phospholipid nanosystem suggests its prospects for practical use.     

Potent antimalarial 4-pyridones with improved physico-chemical properties

Antimalarial 4-pyridones are a novel class of inhibitors of the plasmodial mitochondrial electron transport chain targeting Cytochrome bc1 (complex III). In general, the most potent 4-pyridones are lipophilic molecules with poor solubility in aqueous media and low oral bioavailability in pre-clinical species from the solid dosage form. The strategy of introducing polar hydroxymethyl groups has enabled us to maintain the high levels of antimalarial potency observed for other more lipophilic analogues whilst improving the solubility and the oral bioavailability in pre-clinical species.     

A Self-microemulsifying Drug Delivery System (SMEDDS) for a Novel Medicative Compound Against Depression: a Preparation and Bioavailability Study in Rats

AJS is the code name of an untitled novel medicative compound synthesized by the Tasly Holding Group Company (Tianjin, China) based on the structure of cinnamamide, which is one of the Biopharmaceutics Classification System (BCS) class II drugs. The drug has better antidepressant effect, achieved by acting on the 5-hydroxytryptamine receptor. However, the therapeutic effects of the drug are compromised due to its poor water solubility and lower bioavailability. Herein, a self-microemulsifying drug delivery system (SMEDDS) was developed to improve its solubility and oral bioavailability. AJS-SMEDDS formulation was optimized in terms of drug solubility in the excipients, droplet size, stability, and drug precipitation using a pseudo-ternary diagram. The pharmacokinetic study was performed in rats, and the drug concentration in plasma samples was assayed using the high-performance liquid chromatography-electrospray tandem mass spectrometry (HPLC-MS/MS) method. The optimized formulation for SMEDDS has a composition of castor oil 24.5%, Labrasol 28.6%, Cremphor EL 40.8%, and Transcutol HP 2.7% (co-surfactant). No drug precipitation or phase separation was observed from the optimized formulation after 3 months of storing at 25°C. The droplet size of microemulsion formed by the optimized formulation was 26.08 ± 1.68 nm, and the zeta potential was −2.76 mV. The oral bioavailability of AJS-SMEDDS was increased by 3.4- and 35.9-fold, respectively, compared with the solid dispersion and cyclodextrin inclusion; meanwhile, the C_max of AJS-SMEDDS was about 2- and 40-fold as great as the two controls, respectively. In summary, the present SMEDDS enhanced oral bioavailability of AJS and was a promising strategy to orally deliver the drug.KEY WORDS: bioavailability, HPLC-MS/MS, self-microemulsifying drug delivery system, solubilization, stability     

Determination of saquinavir in human plasma by high-performance liquid chromatography

We developed and characterized a high-performance liquid chromatography (HPLC) assay for the determination of saquinavir, an HIV protease inhibitor, in human plasma samples. Extraction of plasma samples with diethyl ether resulted in quantitative recovery of both saquinavir and its stereoisomer Ro 31-8533 which was used as an internal standard. The assay was performed isocratically using 5 mM H₂SO₄ (pH 3.5) and acetonitrile (75.5:24.5, v/v) containing 10 mM tetrabutylammonium hydrogen sulfate (TBA) as a mobile phase, a Nucleosil 3C8 column kept at 45°C and UV detection at 240 nm. Using this method, saquinavir and Ro 31-8533 can be separated from endogenous substances, and in the concentration range of 5–110 ng/ml the relative standard deviations for the determination of saquinavir were below 5%. The detection limit of saquinavir in human plasma was 1 ng/ml. The usefulness of the method was demonstrated by quantification of saquinavir in plasma of human subjects treated with 600 mg of saquinavir per os or 12 mg intravenously.     

Design of a liquid nano-sized drug delivery system with enhanced solubility of rivaroxaban for venous thromboembolism management in paediatric patients and emergency cases

Abstract

The increasing incidence of venous thromboembolism (VTE) in paediatric population has stimulated the development of liquid anticoagulant formulations. Thus our goal is to formulate a liquid formulation of poorly-water soluble anticoagulant, rivaroxaban (RIVA), for paediatric use and to assess the possibility of its intravenous administration in emergencies. Self-nanoemulsifying drug delivery systems (SNEDDSs) were developed and characterized. SNEDDS constituents were estimated from the saturated solubility study followed by plotting the corresponding ternary phase diagrams to determine the best self-emulsified systems. Thermodynamic stability, emulsification, dispersibility, robustness to dilution tests, in vitro dissolution, particle size, and zeta potential were executed to optimize the formulations. The optimized formulation, that composed of Capryol 90:Tween 20:PEG 300 (5:45:50), increased RIVA solubility (285.7-fold than water), it formed nanoemulsion with a particle size of 16.15?nm, PDI of 0.25 and zeta potential of ?21.8. It released 100.83?±?2.78% of RIVA after 5?min. SNEDDS was robust to dilution with oral and parenteral fluids and showed safety to human RBCs. SNEDDS showed enhanced bioavailability after oral and intravenous administration than the oral drug suspension (by 1.25 and 1.26-fold, respectively). Moreover, it exhibited enhanced anticoagulant efficacy in the prevention and treatment of carrageenan-induced thrombosis rat model.