The Role of Excipients in the Stability of Triamcinolone Acetonide in Ointments.

Degradation of triamcinolone acetonide (TCA) in an ointment was investigated. TCA appeared to be concentrated in propylene glycol (PG) which in turn is dispersed in a lanolin-petrolatum mixture. Two predominant degradation products were identified: a 21-aldehyde and a 17-carboxylic acid. The 21-aldehyde is formed after TCA is oxidized by O2, a reaction that is catalyzed by trace metals. Logically, the content of trace metals has a profound effect on the degradation rate. It was shown that trace metals are extracted from lanolin and petrolatum by PG, increasing the concentration in PG. In accordance with these findings, TCA degrades faster in PG that is present in the ointment formulation than in regular PG. The 21-aldehyde was confirmed to be a primary degradation product, while the 17-carboxylic acid was identified as a secondary degradation product. Based on the mechanism of degradation, the ointment can be stabilized by the addition of sodium metabisulfite which was shown to reside also in the PG phase within the ointment.

Development of a compounded propofol nanoemulsion using multiple non-invasive process analytical technologies.

Propofol is the preferred anaesthetic for induction and maintenance of sedation in critically ill mechanically ventilated COVID-19 patients. However, during the outbreak of the COVID-19 pandemic, regular supply chains could not keep up with the sudden increase in global demand, causing drug shortages. Propofol is formulated as an oil-in-water emulsion which is administered intravenously. This study explores the extemporaneous preparation of a propofol emulsion without specialized manufacturing equipment to temporally alleviate such shortages. A commercially available lipid emulsion (IVLE, SMOFlipid 20 %), intended for parenteral nutrition, was used to create a propofol loaded nanoemulsion via addition of liquid propofol drug substance and subsequent mixing. Critical quality attributes such as mean droplet size and the volume-weighted percentage of large-diameter (>5µm) droplets were studied. The evolution of droplet size and propofol distribution was monitored in situ and non-destructively, maintaining sterility, using Spatially Resolved Dynamic Light Scattering and Near Infrared Spectroscopy, respectively. Using response surface methodology, an optimum was found for a 4 % w/v propofol formulation with a ∼15 min mixing time in a flask shaker at a 40° shaking angle. This study shows that extemporaneous compounding is a viable option for emergency supply of propofol drug product during global drug shortages.

Development and application of a process window for achieving high-quality coating in a fluidized bed coating process.

Next to the coating formulation, process conditions play important roles in determining coating quality. This study aims to develop an operational window that separates layering from agglomeration regimes and, furthermore, the one that leads to the best coating quality in a fluidized bed coater. The bed relative humidity and the droplet size of the coating aerosol were predicted using a set of engineering models. The coating quality was characterized using a quantitative image analysis method, which measures the coating thickness distribution, the total porosity, and the pore size in the coating. The layering regime can be achieved by performing the coating process at a certain excess of the viscous Stokes number (DeltaSt(v)). This excess is dependent on the given bed relative humidity and droplet size. The higher the bed relative humidity, the higher is the DeltaSt(v) required to keep the process in the layering regime. Further, it is shown that using bed relative humidity and droplet size alone is not enough to obtain constant coating quality. The changes in bed relative humidity and droplet size have been identified to correlate to the fractional area of particles sprayed per unit of time. This parameter can effectively serve as an additional parameter to be considered for a better control on the coating quality. High coating quality is shown to be achieved by performing the process close to saturation and spraying droplets small enough to obtain high spraying rate, but not too small to cause incomplete coverage of the core particles.

Study of petrolatum structure: Explaining its variable rheological behavior.

The rheological properties of petrolatum are dependent on both temperature and thermal history. How this thermal dependency can be explained is unclear. In the past it has been suggested that the structure of petrolatum consists of a three-dimensional crystalline network. This has been established using old microscopic techniques only. Therefore a study on the microstructure of petrolatum was conducted using rheometry, DSC, pulsed NMR, polarized light microscopy and synchrotron X-ray. The combination of these techniques show that petrolatum is composed of 21% solid material at room temperature. This consists of partly crystalline lamellar sheets which are packed in stacks. The occurrence of these lamellar sheets is temperature dependent and the number of lamellar stacks is dependent on thermal history. It was shown that rheological differences in petrolatum can be explained by the number of lamellar stacks present, where more lamellar stacks result in more rigid petrolatum.

Development and validation of a stability-indicating HPLC-UV method for the determination of triamcinolone acetonide and its degradation products in an ointment formulation.

A stability indicating high performance liquid chromatography method has been developed for the determination of triamcinolone acetonide (TCA) and its main degradation products in ointment formulations. The method, based on extensive stress testing using metal salts, azobisisobutyronitrile, acid, base and peroxide, showed that TCA undergoes oxidative degradation. All degradation products were identified using HPLC mass spectrometry. Separation and quantification was achieved using an Altima C18 RP18 HP column (250×4.6mm2, with 5µm particles) using a mobile phase consisting of acetonitrile and water buffered at pH 7 using 10mM phosphate buffer. A gradient mode was operated at a flow rate of 1.5ml/min and detection was at 241nm. The method showed linearity for TCA and Impurity C in 0.02-125% of the workload, both square roots of the correlation coefficients were larger than 0.9999. Repeatability and intermediate precision were performed by six consecutive injections of both 1.25% and 125% of the work load for both TCA and Impurity C divided equally over two days. RSD were 0.6% and 0.7% for TCA and 0.5% and 0.1% for Impurity C respectively. Accuracy was determined as well, the average recoveries were 99.5% (±0.1%, n=3) for TCA and 96.9% (±1.3%, n=3) for impurity C respectively from spiked ointment samples. The robustness was also evaluated by variations of column (old vs new), mobile phase pH and filter retention. The applicability of the method was evaluated by analysis of a commercial ointment formulation. Interestingly, the extensive stress tests were able to predict all degradation products of TCA in a long term stability ointment sample.

Topically used corticosteroids: What is the big picture of drug product degradation?

Corticosteroids are widely used in topical formulations such as creams (aqueous) and ointments (non-aqueous). The generally used corticosteroids show large molecular resemblance, where especially the 20-keto-21-hydroxyl group bound to the 17 carbon is important for their chemical stability. Oxidation in both aqueous and non-aqueous environment occurs for triamcinolone acetonide (TCA), hydrocortisone (HC) and desoximethasone (DS). Besides the 20-keto-21-hydroxyl group, TCA, HC and DS have different other moieties attached to the same C17. These moieties are shown to influence not only the type of degradation product formed but also the degradation kinetics. Seven degradation products are found in total and a degradation mechanism is proposed. Furthermore the transesterfication of betamethasone-17-valerate to betamethasone-21-valerate is shown to occur both in aqueous and non-aqueous environment. Finally, a comprehensive scheme of degradation pathways is presented that is applicable for both aqueous and non-aqueous formulations.

The contribution of the in-vivo fate of an oil depot to drug absorption.

Sustained release of lipophilic compounds can be achieved with oil depots. These parenteral formulations are generally injected in the vastus lateralis and deltoid muscle. It is known that the absorption rate differs between these two muscles. The reason for this is not fully understood. The aim of the current study was to investigate the fate of an oil depot in different tissues to elucidate whether the disappearance rate of oil is the cause of observed differences in absorption rate. A study with healthy volunteers was conducted to determine 1.0mL oil depots in the vastus lateralis and deltoid muscle for two weeks. The spatial distribution of the oil depots was determined using MRI. Additionally, a study in rats was conducted to microscopically examine the oil immediately and after 31days of injection. All rats were injected with a 0.1mL oil depot with and without benzyl alcohol (BOH), a commonly used excipient in oil depots. In humans, it was shown that all oil depots were equal in volume and surface area directly after injection. Moreover, the disappearance rate for all oil depots was similar; within one week there was no depot visible anymore by MRI. This in contrast to the depots in rats, which were still microscopically visible after 31days. It is concluded from these observations that the oil is dispersed to small droplets in the course of time. The resulting increase in surface area does not lead to an increase in absorption rate however. The results of this paper show that the variation in drug absorption as found for the two muscles is not caused by a distinction in surface areas or disappearance rates of the oil depots. Therefore, it is argued that the local tissue drainage (e.g. lymph flow) plays a considerable role in drug absorption from oil depots, whereby the lymph flow differs between the muscles.

The influence of cetomacrogol ointment processing on structure: A definitive screening design.

Batch-to-batch variability is a challenge for the industrial scale production of ointments. Therefore the current investigation focussed on identifying and understanding critical process parameters (CPPs) for cetomacrogol ointment. This was evaluated using a definitive screening design (DSD) approach in which fourteen batches were produced under predefined and controlled conditions using the following variables: addition of SiO2 nanoparticles, mixing speed, cooling rate, heating temperature, container filling temperature and isothermal mixing at the filling temperature. Ointment structure was evaluated using a number of rheological parameters. One of these parameters, yield stress was found to be strongly influenced by filling temperature and mixing speed (p=0.0065 and p=0.0013 respectively). Both significantly affect ointment structure and they also have a significant interaction (p<0.05). Understanding the ointment production process can help in defining a processing window to produce ointment of constant quality.

Where does hydrolysis of nandrolone decanoate occur in the human body after release from an oil depot?

Long-term therapy of nandrolone (N) is recommended to increase mineral density and muscle strength. Using a parenteral sustained release drug formulation with nandrolone decanoate (ND), therapeutic N levels can be achieved and maintained. Until now, it is unknown if hydrolysis of ND into N occurs in tissue at the injection site or after systemic absorption. Therefore, hydrolysis studies were conducted to investigate the location and rate of ND hydrolysis after its release from the oil depot. ND hydrolysis was studied in porcine tissues, to mimic the human muscular and subcutaneous tissues. Additionally, the ND hydrolysis was studied in human whole blood, plasma and serum at a concentration range of 23.3-233.3µM. ND hydrolysis only occurred in human whole blood. The hydrolysis did not start immediately, but after a lag time. The mean lag time for all studied concentrations was 34.9±2.5min. Because of a slow penetration into tissue, hydrolysis of ND is found to be very low in surrounding tissue. Therefore the local generation of the active compound is clinically irrelevant. It is argued that after injection of the oil depot, ND molecules will be transported via the lymphatic system towards lymph nodes. From here, it will enter the central circulation and within half an hour it will hydrolyse to the active N compound.

Spatial distribution of oil depots monitored in human muscle using MRI.

Oil depots are parenteral drug formulations meant for sustained release of lipophilic compounds. According to mass transport models, the drug-release rate from these injections is determined by the surface area of the oil depot. Until now, the size of the surface area of injected depots has not been assessed, however. MRI provides an excellent possibility to distinguish between water and adipose tissue. The aim of this study was to investigate whether MRI can be used to determine the shape and hence the surface area of oil depots in muscle tissue. The developed MRI-scan protocol is demonstrated to be suitable for visualising oil depots. It was applied to determine the surface area of 0.5mL oil, i.m. injected in healthy volunteers. The mean (±RSD) surface area and volume of the depots recovered after injection was 755.4mm(2) (±26.5) and 520.1mm(3) (±24.6). It is shown that the depot disappearance from the injection site is very variable between volunteers. It is suggested that the oil is first solubilized and subsequently distributed. In all cases, the oil was not detectable after 14days. These factors are relevant for the understanding of the mechanism by which compounds are released out of oil depots.

Effect of supersaturation and crystallization phenomena on the release properties of a controlled release device based on EVA copolymer.

This study describes the influence of steroid concentration, manufacturing and storage on the release properties of etonogestrel from polyethylene vinylacetate (EVA) based coaxial fibers. Coaxial fibers were manufactured by extrusion technology. As a consequence of the high extrusion temperatures large amounts of etonogestrel dissolve in the polymeric melt. Since the release from the coaxial fibers is directly proportional to the concentration gradient over the membrane, the amount of dissolved drug that recrystallizes upon cooling is of crucial importance. Therefore crystallization kinetics were studied using thermal analysis and hot stage microscopy. It was found that if the amount of etonogestrel is below a critical nucleation concentration at room temperature, the dissolved steroid remains in a supersaturated state. If on the other hand the amount of dissolved steroid is just above the critical nucleation concentration, the supersaturated steroid recrystallizes very slowly. It is concluded that the release of etonogestrel from an extruded coaxial fiber is a result of a complicated set of parameters, where, respectively process conditions, concentration of etonogestrel and both time and temperature of storage are of importance.

Relationship between inhomogeneity phenomena and granule growth mechanisms in a high-shear mixer.

A poorly understood phenomenon observed during high-shear granulation is the poor distribution of a drug in the granulate. To investigate the causes of this inhomogeneity, lactose of three different particle sizes was granulated with 0.1% micronized estradiol (5 microm) in a 10 l high-shear mixer. An aqueous solution of HPC was used as binder. Granulation with the largest lactose particles (141 microm) yielded a homogeneous granulate. However, at a prolonged process time demixing was observed. Contrary to the largest particles, granulation with the smaller lactose particles (50 and 23 microm) already leads to demixing in the first minute, although to a lesser extent. It was concluded that granulation with the largest particles resulted in breakage behavior of the granulate, thereby preventing demixing. However, once granules are strong enough (smaller particle size and prolonged process time) to survive the shear forces demixing is observed. Theoretical calculations of dynamic and static granule strength were used to explain the influence of lactose particle size and process time on breakage behavior. It was argued that once granules survive, preferential growth of the small estradiol particles in favor of the larger lactose particles causes the demixing. The extent of demixing depends on the particle size difference.

In vitro release properties of etonogestrel and ethinyl estradiol from a contraceptive vaginal ring.

The release properties of steroids from a combined contraceptive vaginal ring have been investigated. The product design is based on a coaxial fiber consisting of two types of polyethylene vinylacetate copolymers. Inside the core of the fiber, two steroids are present in a molecularly dissolved state. In order to design a controlled release system with specified release characteristics, values of diffusion coefficient and solubility are required. These data can either be determined during pre-formulation studies on e.g. polymeric flat films or from in-vitro release measurements of the actual coaxial fibers. It can be concluded from this study that polyethylene vinylacetate copolymers exhibit suitable properties to develop a controlled release system with the two steroids etonogestrel and ethinyl estradiol. It has been found that the permeability data obtained in the pre-formulation studies are useful in semi-quantitative terms, but deviate from the permeability data found from the in-vitro release of coaxial fibers. This is most likely due to differences in the polymeric structure of films and coaxial fibers. As a consequence, further studies should be initiated to evaluate the relationship between the manufacturing process and the resulting polymeric structure. It has also been found that the solubility and release of etonogestrel are influenced by the concentration of ethinyl estradiol. By investigating this phenomenon by thermoanalysis, it was shown that the steroids form an eutectic. The lower melting point of the steroids results in an increase in solubility and hence in altered permeability properties.

Quantitative image analysis for evaluating the coating thickness and pore distribution in coated small particles.

PURPOSE: This study aims to develop a characterization method for coating structure based on image analysis, which is particularly promising for the rational design of coated particles in the pharmaceutical industry. METHODS: The method applies the MATLAB image processing toolbox to images of coated particles taken with Confocal Laser Scanning Microscopy (CSLM). The coating thicknesses have been determined along the particle perimeter, from which a statistical analysis could be performed to obtain relevant thickness properties, e.g. the minimum coating thickness and the span of the thickness distribution. The characterization of the pore structure involved a proper segmentation of pores from the coating and a granulometry operation. RESULTS: The presented method facilitates the quantification of porosity, thickness and pore size distribution of a coating. These parameters are considered the important coating properties, which are critical to coating functionality. Additionally, the effect of the coating process variations on coating quality can straight-forwardly be assessed. CONCLUSIONS: Enabling a good characterization of the coating qualities, the presented method can be used as a fast and effective tool to predict coating functionality. This approach also enables the influence of different process conditions on coating properties to be effectively monitored, which latterly leads to process tailoring.

Influence of enzymes and surfactants on the disintegration behavior of cross-linked hard gelatin capsules during dissolution.

Gelatin exhibits cross-linking upon storage at stress conditions. Capsules stored at these conditions fail to show appropriate in vitro dissolution. The aim of this study is to show the effect of surfactants in the medium on the disintegration of the gelatin capsule. This is demonstrated in the presence and absence of the enzymes pancreatin and pepsin, the function of which is to improve the dissolution. Sodium lauryl sulfate (SLS) and Tween 80 are tested as surfactants. When SLS is used in the medium, dissolution is significantly hampered due to the formation of a less soluble precipitate of gelatin. Compared to SLS, Tween 80 shows far better disintegration and solubility results in dissolution media with neutral or low pH. Therefore, it is concluded in this study that Tween 80 is preferred when a surfactant is necessary to comply with sink condition requirements.

Effects of high-shear granulation on granulate homogeneity.

This study considers the effects of particle size of the powder constituents, and of impeller speed on the homogeneity of drug distribution on granulations produced in high-speed mixers. When a micronized low-dose steroid hormone was granulated together with unmicronized lactose in a Vactron 75 high-shear granulator at 250 rpm, strong inhomogeneities of the drug distribution arose. The coarse particle size fractions of the granules were found to be superpotent up to 150% of the mean drug content, whereas the fine size fraction showed a corresponding subpotency of 50%. Both particle size and impeller speed attributed to this phenomenon. At an impeller speed of 75 rpm, a significantly better drug distribution was obtained. Results show that the inhomogeneities found are mainly a consequence of the balance between the impact pressure as exerted by the impeller on the one hand and the shear resistance of the nuclei on the other hand. At a speed of 250 rpm, the tensile strength of 3 x 10(3) N/m2 of the initially formed nuclei is too weak to resist an impact pressure of 30 x 10(3) N/m2. For that reason, particle rearrangement takes place, which results in inhomogeneity. Because an impeller speed of 75 rpm is equal to an impact pressure of 2.6 x 10(3) N/m2, significantly less demixing occurs. Similar results can be obtained when the particle size of all constituents is reduced, which increases the tensile strength of the nuclei.

Rectal absorption of metronidazole from polyethylene glycol suppositories.

The rectal absorption of metronidazole from an aqueous suspension, a fatty suppository and three different polyethylene glycol suppositories was studied in healthy volunteers and compared with absorption from an oral solution. Rectal absorption was found to be rather slow for all suppositories. Of all rectal dosage forms, the polyethylene glycol suppositories gave the highest peak plasma levels and the highest relative bioavailability. Compared with oral administration, a relative bioavailability of 80% could be obtained.

Citrate increases glass transition temperature of vitrified sucrose preparations.

The aim of this study was to investigate the effect of sodium citrate on the properties of dried amorphous sucrose glasses. Addition of sodium citrate to a sucrose solution followed by freeze-drying or convective drying resulted in a glass transition temperature (Tg) that was higher than the well-studied sucrose Tg. This result was obtained either at reduced water content of the analysed sample or by removal of water during Modulated DSC analysis. After removal of the remaining water ( < 3.5% w/w), a Tg of approximately 105 degrees C was obtained at a mass ratio of sodium citrate to sucrose of 0.3. FTIR analysis showed a similar increase in Tg as was found with Modulated DSC analysis. The Tg values were derived from breaks in the vibrational frequency vs. temperature plots in the OH stretching and bending regions. Elevated average strength of hydrogen bonding in the sucrose/citrate glass was concluded from the downshift of the OH stretching band of 25 cm(-1) and from the reduced wavenumber temperature coefficient (WTC). The antisymmetric carboxylate stretch of citrate sensed the glass transition of the mixture, from which we conclude that citrate interacts with the sucrose OH via its carboxylate groups.

Vial lyophilization: calculations on rate limitation during primary drying.

PURPOSE: The aim of this study was to assess the rate limiting factors in the sublimation phase of freeze drying and to propose a simple model on the basis of these rate limitations. METHODS: A programmable freeze dryer was used. The load consisted of vials of varying size and various contents. To increase heat transfer, conductive paste was applied while the resistance toward mass transport was varied by using different restrictive capillaries. RESULTS: It was found that heat transfer limits the rate of sublimation. Presence of the commonly used excipient mannitol did not have a consequence on the rate of sublimation. The same applied for the restrictions towards mass transport. It was found that there exists not only a barrier against heat transport under the vial, but also between the glass wall and the frozen solution. CONCLUSIONS: From the results, a set of equations is proposed that enables to predict optimum sublimation conditions. For the pharmaceutical technologist this can serve as a simple and useful tool to derive a suitable freeze drying program.

Identity-by-descent mapping of recessive traits in livestock: application to map the bovine syndactyly locus to chromosome 15.

Twelve animals affected with syndactyly or mulefoot were sampled in the Dutch black-and-white cattle population. Analysis of the pedigree data reveal that all of these individuals traced back to a single acknowledged carrier founder individual. Between seven and nine generations separated the founder from its 12 affected descendents. The 12 affected offspring were genotyped for a battery of 213 microsatellites spanning the 29 bovine autosomes. The resulting genotypes were analyzed using a maximum likelihood approach searching for shared homozygous haplotypes among affected individuals. Three candidate regions for the syndactyly locus emerged from this initial screening. syndactyly was shown to map to one of these candidate regions on chromosome 15 by genotyping 29 additional individuals linking founder and affected offspring and performing a conventional linkage analysis with the LINKAGE programs. This study illustrates the potential of identity-by-descent mapping in livestock populations.