Formulation study of a patch containing propranolol by design of experiments

Objective: To evaluate the feasibility of a transdermal patch containing propranolol (PR).

Method: Skin penetration enhancers (SPEs) able to improve the skin permeability of PR were selected and a quality by design approach was applied to the development of the patch by a 2⁴ full factorial design. The permeation profile of PR from the formulations was assessed in in vitro permeation studies performed by using Franz diffusion cells and human epidermis as membrane. Finally, skin irritation was evaluated by the Draize test.

Results: N-methyl pyrrolidone (NMP) resulted as the best SPE: in addition, the critical factors influencing the PR diffusion through the human epidermis when loaded in the patch resulted in the matrix thickness (X₁, p?=?0.0957) and PR content (X₃, p?=?0.0004) which improved the flux; conversely, NMP lacked its enhancement effect when loaded in the patch and the increase in its concentration (X₄, p?=?0.006) affected the drug permeation through human epidermis. The flux of optimal formulation was 12.7?μg/cm²/h. On the basis of the steady-state concentration and clearance of PR, the estimated patch surface was 100–120 cm², since the activity of PR is related to its Senantiomer and no in vivo bioconversion occurs.

Conclusion: A patch containing (S)-PR was prepared and the (S)-PR flux (13.3?μg/cm²/h) permitted to confirm the suitability of a transdermal administration of PR. In particular, the use of a 50?μm thick methacrylic matrix containing 8% (S)-PR and 15% NMP can allow to develop a patch non-irritating to the skin, in order to ensure a constant permeation flux of PR over 48?h.     

Characterization of an antioxidant surfactant-free topical formulation containing Castanea sativa leaf extract

Context: Inclusion of antioxidants in topical formulations can contribute to minimize oxidative stress in the skin, which has been associated with photoaging, several dermatosis and cancer.

Objective: A Castanea sativa leaf extract with established antioxidant activity was incorporated into a semisolid surfactant-free formulation. The objective of this study was to perform a comprehensive characterization of this formulation.

Materials and methods: Physical, microbiological and functional stability were evaluated during 6?months storage at 20?°C and 40?°C. Microstructure elucidation (cryo-SEM), in vitro release and in vivo moisturizing effect (Corneometer® CM 825) were also assessed.

Results and discussion: Minor changes were observed in the textural and rheological properties of the formulation when stored at 20?°C for 6?months and the antioxidant activity of the plant extract remained constant throughout the storage period. Microbiological quality was confirmed at the end of the study. Under accelerated conditions, higher modifications of the evaluated parameters were observed. Cryo-SEM analysis revealed the presence of oil droplets dispersed into a gelified external phase. The release rate of the antioxidant compounds (610?±?70?µgh^?0.5) followed Higuchi model. A significant in vivo moisturizing effect was demonstrated, that lasted at least 4?h after product’s application.

Conclusion: The physical, functional and microbiological stability of the antioxidant formulation was established. Specific storage conditions should be recommended considering the influence of temperature on the stability. A skin hydration effect and good skin tolerance were also found which suggests that this preparation can be useful in the prevention or treatment of oxidative stress-mediated dysfunctions.     

In vitro models to estimate drug penetration through the compromised stratum corneum barrier

Objectives: The phospholipid vesicle-based permeation assay (PVPA) is a recently established in vitro stratum corneum model to estimate the permeability of intact and healthy skin. The aim here was to further evolve this model to mimic the stratum corneum in a compromised skin barrier by reducing the barrier functions in a controlled manner. Methods: To mimic compromised skin barriers, PVPA barriers were prepared with explicitly defined reduced barrier function and compared with literature data from both human and animal skin with compromised barrier properties. Caffeine, diclofenac sodium, chloramphenicol and the hydrophilic marker calcein were tested to compare the PVPA models with established models. Results and discussions: The established PVPA models mimicking the stratum corneum in healthy skin showed good correlation with biological barriers by ranking drugs similar to those ranked by the pig ear skin model and were comparable to literature data on permeation through healthy human skin. The PVPA models provided reproducible and consistent results with a distinction between the barriers mimicking compromised and healthy skin. The trends in increasing drug permeation with an increasing degree of compromised barriers for the model drugs were similar to the literature data from other in vivo and in vitro models. Conclusions: The PVPA models have the potential to provide permeation predictions when investigating drugs or cosmeceuticals intended for various compromised skin conditions and can thus possibly reduce the time and cost of testing as well as the use of animal testing in the early development of drug candidates, drugs and cosmeceuticals.     

In-vitro and in-vivo evaluation of ciprofloxacin liposomes for pulmonary administration

Objective: The aim of this study was to investigate the ciprofloxacin liposome of high encapsulation efficiency with optimal physical properties for pulmonary administration and to test its in-vivo potential in rats.

Methods: Ciprofloxacin-loaded liposome was prepared by gradient of ammonium sulfate method. The particle size and morphology were determined using a NANOPHOX particle size analyzer and a transmission electron microscope, respectively. Encapsulation efficiency was calculated by UV spectrophotometry. Ciprofloxacin liposome released in vitro was performed using simulated lung fluid. In-vivo studies, pharmacokinetics and pulmonary distribution, HPLC method was established to determine the concentration of ciprofloxacin in rat plasma and lung tissue. The pulmonary pathological section was used to observe the change of pulmonary pathology.

Results: The optimized ciprofloxacin liposome, which had a high encapsulation efficiency of 93.96%, and an average particle size of 349.6?nm with a span of 0.42, showed sustained in-vitro release. The optimized ciprofloxacin liposome was further examined in the in-vivo study in rats. The concentration of ciprofloxacin in lung and blood was simultaneously determined in each rat. The ratio of the AUC_lung value between ciprofloxacin liposome and ciprofloxacin solution was 288.33, whereas the relative bioavailability was 72.42%, and the drug targeting efficiency of ciprofloxacin liposome and ciprofloxacin solution by intratracheal administration were 799.71 and 2.01, respectively.

Conclusion: Ciprofloxacin liposome for pulmonary administration offered an attractive alternative that was able to deliver high concentrations of antibiotic directly to the chosen target site while minimizing the local irritation.     

Formulation and characterization of liquid crystal systems containing azelaic acid for topical delivery

Purpose: The aim of this study is to prepare and characterize azelaic acid (AzA) containing liquid crystal (LC) drug delivery systems for topical use.

Methods: Two ternary phase diagrams, containing liquid paraffin as the oil component and a mixture of two nonionic surfactants (Brij 721P and Brij 72), were constructed. Formulations chosen from the phase diagrams were characterized by polarized light microscopy, rheological analyses, differential scanning calorimetry (DSC), and small angle x-ray scattering spectroscopy.

Results: Polarized light microscopy proved that except the oil/water emulsion (O/W E), other formulations showed lamellar LC structure. In vitro release studies indicated that the fastest release was achieved by the Lamellar LC (LLC) and O/W E systems, whereas slower release was obtained from the emulsion containing lamellar LC (E-LLC) and distorted lamellar LC (D-LLC) systems. Results of rheological measurements both supported the results of in vitro release studies and showed that the emulsion containing the LC (E-LLC) system had the most stable structure. The formulations and their effect on stratum corneum (SC) were evaluated by DSC studies. The lamellar LC (LLC), emulsion containing lamellar liquid crystal (E-LLC), and O/W E formulations had an effect on both lipid and protein components of SC, whereas distorted lamellar liquid crystal (D-LLC) system had an effect on only the lipid components of SC.

Conclusions: LLC systems could be considered promising for the topical delivery of AzA.     

Preparing of aspirin sustained-release granules by hot-melt granulation and micro-crystal coating

In this work, aspirin (ASP) sustained granules were prepared using micro-crystal coating and hot-melt granulation, respectively. In the process of micro-crystal coating, PVP was used to form the isolation layer and then coated with either Eudragit RS/RL30D or ethyl cellulose (EC) as sustained-release layers to prepare sustained granules (the granules from this method were denoted m-cG). And in the process of hot-melt granulation, the granules were obtained with stearyl alcohol as a binder and EC as matrix material to prepare sustained granules (the granules were denoted h-mG). The in vitro release of ASP sustained-release granules was investigated by dissolution apparatus and the stability of the granules was studied. Since both methods effectively prevented the hydrolysis of ASP, the sustained granules by micro-crystal coating and hot-melt granulation were stable. However, there was a clear difference in the in vitro release of h-mG and m-cG. The h-mG was completely released in 4?h, while the m-cG with EC as sustained-release layer released 80% in 24?h and the m-cG with the Eudragit RS/RL 30?D as sustained-release layer released completely in 5?h. The results showed that micro-crystal coating was more suitable for the preparation of ASP sustained granules, and the granules with EC as sustained layer could achieve a better sustained-release effect.     

Development and characterization of stabilized double loaded mPEG-PDLLA micelles for simultaneous delivery of paclitaxel and docetaxel

Objective: Double loaded micelles (DLM) in which paclitaxel (PTX) and docetaxel (DTX) were co-solubilized with monomethoxy poly(ethylene glycol)-block-poly(d,l-lactide) (mPEG-PLA) copolymer were prepared and evaluated in an aim to investigate the effect of a combination of PTX and DTX on the stability of mPEG-PLA micelles compared to single drug-loaded micelles (SDM), especially that recent clinical anticancer formulations are limited by the existence of toxic excipients and stability issues.

Materials and methods: The SDM and DLM of PTX and DTX were prepared by a solvent evaporation method. Micellar size, size distribution, drug loading content and drug release were investigated. Transmission electron microscopy was used to investigate the stabilization mechanism.

Results: The drug loading efficiency of both PTX and DTX in DLM and SDM were 25% and 10%, respectively. ¹H NMR showed a successful encapsulation of both drugs in the polymeric micelle. DLM showed better physical stability at drug concentrations higher than 1?mg/mL compared to SDM. Moreover, DLM, SDM-PTX and SDM-DTX were stable for 24, 9 and 1?h, respectively. The stabilization mechanism of DLM was investigated, a network structure of DLM was observed in TEM graphs. Furthermore, DLM showed complete and faster drug release compared to SDM. mPEG-PLA double loaded micelles can deliver two poorly water soluble anticancer drugs at clinically relevant doses. The obtained results offer a promising alternative for double drug therapy without any formulation associated undesirable effects and encourage further in vivo development and optimization of the DLM as a drug delivery system for anticancer drugs.     

In vitro stability and compatibility of tenecteplase in central venous access devices

Central venous access devices (CVADs) aid in the delivery of nutritional support, infusion therapy, and hemodialysis. Maintaining continuous flow through these devices is challenging, because they are susceptible to complications such as thrombi occlusion. Therefore, CVADs may require treatment with anticoagulant or thrombolytic agents. Using these agents as locking solutions has been widely investigated; however, few publications have described the compatibility of the therapeutic with the CVAD itself. The objective of this investigation was to evaluate the in vitro stability and compatibility of a thrombolytic biologic agent, tenecteplase, with various CVAD materials. Tenecteplase was reconstituted to 1 mg/mL with either sterile water for injection or bacteriostatic water for injection (0.9% benzyl alcohol) then incubated in glass vials, polysulfone/silicone vascular access ports, and polyurethane or silicone catheters for up to 96 hours. Biochemical assays including protein monomer, protein one-chain, and in vitro bioactivity were used to assess tenecteplase's compatibility with the investigated diluents and materials every 24 hours. Antimicrobial testing was also performed for up to 28 days on bacteriostatic water for injection-reconstituted samples only. Our results showed tenecteplase to be compatible with both types of diluents (in glass vials) and catheters for up to 72 hours. Furthermore, tenecteplase was compatible with the polysulfone/silicone vascular access ports for up to 24 hours. Finally, bacteriostatic water for injection-reconstituted tenecteplase effectively met USP criteria for the inhibition of growth of micro-organisms. This study serves as an example of a best practice to evaluate the in vitro stability and compatibility of a biologic agent with CVAD materials.     

The effect of lipid and aqueous solubilities on flux of nicotinic acid esters from water through silicone membrane

Objective: The maximum fluxes (J_M) of nicotinic acid esters (NAE) across silicone membranes from water (J_MPAQ) have been measured to determine how well they correlate with J_M of NAE across human skin from water in vitro (J_MHAQ) and in vivo (J_MHAQ1) and with J_M of NAE across hairless mouse skin from water (J_MMAQ).

Materials and methods: The NAE were all commercially available. Solubilities in water (S_AQ), isopropyl myristate (S_IPM) and octanol (S_OCT) were obtained from literature sources. J_MPAQ were measured at saturation for all the esters except the methyl ester. In that case, flux was measured at a concentration (C) less than saturation (J_PAQ) and converted to J_MPAQ = (J_PAQ)(S_AQ/C_AQ).

Results and discussion: J_MPAQ values predicted from the previously reported coefficients to the parameters in the Roberts-Sloan (RS) equation (PRE J_MPAQ) were substantially lower than the experimental J_MPAQ values (EXP J_MPAQ) values obtained here. The EXP J_MPAQ were incorporated into the previous J_MPAQ database and new coefficients were obtained: x = ?1.837; y = 0.742; z = 0.00435; r² = 0.86. Correlation of J_MPAQ values with J_MHAQ, J_MHAQ1, and J_MMAQ values show the same trend as the J_MPAQ values.

Conclusions: The inclusion of the NAE n = 6 data into the previous n = 32 database for the permeation of the prodrugs through a silicone membrane from water (J_MPAQ) greatly improved the fit of the n = 38 database to the RS equation: r² = 0.86 vs r² = 0.77. The correlation between log J_MHAQ and log J_MPAQ gave r² = 0.98. This suggests that J_MPAQ values are good predictors of J_MHAQ values.     

Preparation,characterization, sterility validation,and in vitro cell toxicity studies of microemulsions possessing potential parenteral applications

Context: Water-in-oil microemulsions (w/o ME) are ideal for parenteral drug delivery. However, no such formulations have been tested for biocompatibility in in vitro cell cultures. Furthermore, sterilization of w/o MEs is a challenging process that has not been previously developed and validated.

Purpose: To formulate pharmaceutically relevant water-in-oil (w/o) microemulsion’s systems suitable for use as a parenteral formulation.

Methods: w/o MEs were prepared using dioctyl sodium sulfosuccinate (DOSS), ethyl oleate (EO), and water. Formulations were characterized using polarized light microscopy, electrical conductivity, rheology, and dynamic light scattering. An aseptic filtration method for sterilization was developed using membrane filtration. The biocompatibility of selected MEs were evaluated in NIH3T3 cell cultures. Dissolution studies were performed on microemulsions containing methylene blue to evaluate the drug release profile.

Results: The maximum amount of water incorporated in the formulations was 14% w/w. DOSS/EO/water microemulsions exhibited Newtonian flow. Particle sizes for these MEs were less than 30 nm in size. Formulations filtered aseptically were free of bacteria when gram-stained and visualized under a microscope. All MEs showed no toxicity to NIH 3T3 cells.

Discussion: The absence of birefringence and low conductivity values indicated that the formulations were w/o microemulsions. The filtration method of sterilization was validated by the absence of microbial growth on blood agar plates over a 14-day period. In vitro dye release studies demonstrate sustained release of the model drug over a 72-h time period.

Conclusion: Characteristics delineated in this study demonstrate the potential for these formulations to be used as parenteral preparations.