Limitations and Challenges in the Stability of Cysteamine Eye Drop Compounded Formulations

Accumulation of cystine crystals in the cornea of patients suffering from cystinosis is considered pathognomonic and can lead to severe ocular complications. Cysteamine eye drop compounded formulations, commonly prepared by hospital pharmacy services, are meant to diminish the build-up of corneal cystine crystals. The objective of this work was to analyze whether the shelf life proposed for six formulations prepared following different protocols used in hospital pharmacies is adequate to guarantee the quality and efficacy of cysteamine eye drops. The long-term and in-use stabilities of these preparations were studied using different parameters: content of cysteamine and its main degradation product cystamine; appearance, color and odor; pH and viscosity; and microbiological analysis. The results obtained show that degradation of cysteamine was between 20% and 50% after one month of storage in the long-term stability study and between 35% and 60% in the in-use study. These data confirm that cysteamine is a very unstable molecule in aqueous solution, the presence of oxygen being the main degradation factor. Saturation with nitrogen gas of the solutions offers a means of reducing cysteamine degradation. Overall, all the formulae studied presented high instability at the end of their shelf life, suggesting that their clinical efficacy might be dramatically compromised.

Development and Validation of an HPLC Method for the Quantification of Morin Flavonoid Encapsulated within PLGA Nanoparticles

Background:

Morin flavonoid exerts neuroprotective effects with potential interest in neurodegenerative disorders. For this, the use of surface-modified polymeric nanoparticles loaded with morin is an interesting approach.

Objective:

To develop and validate an HPLC method for the quantification of morin released from a new delivery system consisting of poly lactic-co-glycolic (PLGA) nanoparticles functionalized with the dipeptide phe-phe (phenylalanine-phenylalanine) used to facilitate their access to the CNS.

Method:

The HPLC procedure was developed and validated with morin hydrate dissolved either in methanol (method A) or in methanol: 0.1N HCl (50:50, v/v, method B). Two new nanoparticle formulations were developed and characterized: morin-loaded PLGA nanoparticles (formulation F1), and morin-loaded PLGA phe-phe nanoparticles (formulation F2).

Results:

Method A was linear within the concentration range of 5-30 μg.mL-1 and, 1-30 μg mL-1 for method B. LOD and LOQ with method A were 1.23 μg.mL-1 and 3.90 μg.mL-1, respectively, and 0.481 μg.mL-1 and 1.458 μg.mL-1, respectively for method B. The average amount of phe-phe bound to formulation F2 (50 mg of NPs) was 431.33 μg. The encapsulation efficiency of morin within PLGA nanoparticles was around 80%. After functionalization, this value decreased significantly.

Conclusion:

Method B showed better sensitivity, accuracy and precision for the quantification of morin. The procedure used to functionalize the nanoparticles was adequate for linking the dipeptide to their surfaces, but this procedure is not adequate when encapsulating water-soluble compounds.

In vivo toxicity of the ribosome-inactivating lectin ebulin f in elderly mice

Ebulin f is a ribosome-inactivating protein (RIP) present in green fruits of the dwarf elder (Sambucus ebulus L). Since dwarf elder fruits are used for food and as a medicine, we assessed the study of toxicological effects and safety of ebulin f in elderly mice, comparing these results with those reported in young animals and with other RIPs. Female Swiss mice aged 6 and 12 months of age were intraperitoneally injected with a single dose from 1.4 to 4.5 mg/kg ebulin f. Heart, stomach, intestines, lung, kidney, liver, spleen, pancreas, adrenal gland, uterus, ovary and brain were studied. Histology analysis was carried out by staining with hematoxylin and eosin and Masson's trichrome observed with a light microscope, or apoptosis detection by TUNEL method observed with a confocal laser microscope. Treated animals injected with the lower dose could recover their weights, but after 14 days half of them died. The higher dose caused a progressive loss of body weight leading to death. In the animals of the experimental groups it was found atrophy of Lieberkühn's crypts, pneumonia, nephronal degeneration, myocardial atrophy, centrolobular hepatic necrosis, splenic white pulp necrosis foci and increased rate of apoptosis in the intestines and liver, in which apoptoses were mainly located in the vicinity of the lobular central vein. We conclude that ebulin f affects vital organs in elderly mice.

Paneth cells are also target of the ribotoxic lectin nigrin b

Ribosome-inactivating lectins (RILs) are A-B type toxins like ricin whose molecular target is the large rRNA of eukaryotic ribosome. Administration of lethal doses of the RIL nigrin b isolated from elderberry (Sambucus nigra L.) bark triggers specific intestinal derangement. The aim of the present research was to explore the early effects of a lethal dose of nigrin b (16 mg/kg body weight) on the small intestine using light and electron microscopy to ascertain intestinal epithelium changes. 6 h after nigrin administration, the small intestine crypts began to show signs of damage with cells appearing at different stages of apoptosis. 16 h after injection crypts appeared more impaired, including the derangement of Paneth cells. The novelty of our results is that the Paneth cells in the small intestine in addition to stem cells are the early cellular targets for nigrin b.

Transient injury-dependent up-regulation of CD105 and its specific targeting with an anti-vascular anti-mouse endoglin-nigrin b immunotoxin

Endoglin (CD105), a cell-surface co-receptor for transforming growth factor-beta (TGF-β) superfamily members, is over-expressed in tumor neovasculature and can be targeted with anti-endoglin antibodies, thus becoming an important tool for anti-tumoral therapy. Injury of the mouse tail induced the transient expression of endoglin, this peaking at three days after injury and disappearing six days later. An immunotoxin containing the anti-mouse endoglin rat monoclonal antibody MJ7/18 and the non-toxic ribosome-inactivating protein nigrin b (Ngb) was found to be very active in targeting mouse endoglin in the L929 fibroblast cell line (IC(50) of 4 x 10(-11) M). At that concentration, the immunotoxin lacked unspecific activity. Upon induction of endoglin after injury, the MJ7-Ngb immunotoxin strongly attacked and deranged the injured tail, inducing tissue damage. Such effects were dependent on the age of the animals and were evident in six-week-old mice, but not in eight-month-old mice. Our results indicate that endoglin is up-regulated in newly formed vessels upon injury and can be targeted by the MJ7-Ngb immunotoxin; thus, it could be a useful tool for tumor ablation research.

In vitro and in vivo effects of an anti-mouse endoglin (CD105)-immunotoxin on the early stages of mouse B16MEL4A5 melanoma tumours

TGF-beta superfamily co-receptors are emerging as targets for cancer therapy, acting both directly on cells and indirectly on the tumour neovasculature. Endoglin (CD105), an accessory component of the TGF-beta receptor complex, is expressed in certain melanoma cell lines and the endothelial cells of tumour neovessels. Targeting endoglin with immunotoxins is an attractive approach for actively suppressing the blood supply to tumours. Here, we report evidence indicating that endoglin is expressed in mouse melanoma B16MEL4A5 and mouse fibroblast L929 cell lines. We prepared an immunotoxin to target endoglin by coupling the rat anti-mouse MJ7/18 (IgG2a) monoclonal antibody (mAb) to the non-toxic type 2 ribosome-inactivating protein nigrin b (Ngb) with N-succinimidyl 3-(2-pyridyldithio)-propionate (SPDP) as a linker with a molar nigrin b at a MJ7/18 stoichiometry of 2:1. The MJ7-Ngb immunotoxin generated killed both cell lines, with IC50 values of 4.2 × 10(-9) M for B16MEL4A5 and 7.7 × 10(-11) M for L929 cells. For in vivo assays of the immunotoxin, B16MEL4A5 cells were injected subcutaneously into the right flanks of 6-week-old C57BL/6 J mice. When the animals developed palpable solid tumours, they were subjected to treatment with the immunotoxin. While treatment with either MJ7/18 mAb or Ngb did not affect tumour development, treatment with the immunotoxin completely and steadily blocked tumour growth up to 7 days, after which some tumours re-grew. Thus, vascular-targeting therapy with this anti-vascular immunotoxin could promote the destruction of newly created tumour vessels at early stages of B16MEL4A5 tumour development and readily accessible CD105+ B16MEL4A5 melanoma cells.

Elastic vesicles of sumatriptan succinate for transdermal administration: characterization and in vitro permeation studies

Elastic liposomes, including sumatriptan succinate, were prepared for their transdermal administration. Lipid vesicles containing 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or l-α-phosphatidylcholine dilauroyl (DLPC) phospholipids were characterized for various parameters, including size, particle-size distribution (i.e., polydispersity index), and elasticity. In vitro transdermal experiments for the study of the skin penetration of sumatriptan succinate contained in liposomes were performed by using flow-through diffusion cells. The diameter of sumatriptan liposomes with different lipid compositions varied between 279 and 282 nm, and the polydispersity index value for the size distribution of liposomal formulations was <0.5. DLPC vesicles proved to be more elastic and provided a higher sumatriptan transdermal flux than vesicles formulated with DOPC phospolipid.

A stability study of tetracycline and tetracycline cyclodextrins in tablets using a new HPLC method

A sensitive, rapid, reproducible, easy and precise reverse-phase high-performance liquid chromatographic assay for stability studies of tetracycline hydrochloride (TC.HCl) formulated with different excipients and techniques without using gradient elution, extraction methods, and at ambient temperature has been developed and validated. The method was especially developed for the analysis of TC.HCl and its main degradation product, 4-epi-anhydrotetracycline, due to its toxicity, in samples obtained from stability studies of solid dosage forms (tablets). The influence of the excipients used for the pharmaceutical design of the different tablet formulations and the use of hydroxypropyl-beta-cyclodextrin on the stability were evaluated. A significant improvement of the stability of TC.HCl was found in some tablet formulations. The precision and accuracy of the method was also studied for the encapsulated TC.HCl, and no significant interferences were found. The results obtained suggested that the developed HPLC method is selective and specific for the analysis of TC.HCl samples, and that it can be applied for long-term and accelerated protocols for stability studies.

Effect of pharmacotechnical design on the in vitro interaction of ketoconazole tablets with non-systemic antacids

In certain polytherapy programs, ketoconazole can be administered with some antacids that could modify its dissolution rate and reduce its absorption leading to therapeutic failures. The aim of this work was to evaluate the influence of some excipients on this interaction in vitro. In this way, six formulations of directly compressible ketoconazole tablets were developed. The results confirmed that the dissolution rate of ketoconazole tablets was significantly reduced in the presence of antacids. Nevertheless this interaction was remarkably avoided in some of the formulations checked and in some conditions. In this way, the inclusion of a disintegrant (sodium starch glycolate) not only increased the dissolution rate of ketoconazole in the tablets, as expected, but it also modified the degree in which the dissolution rate was decreased in the presence of antacids. It was proved that a suitable selection of the excipients and therefore the modification in the rate in which the drug was released, could play an important role to modify a pharmacokinetic interaction based on a reduction of the solubility of the drug as a function of the pH value of the medium.

Validation protocol of an automated in-line flow-through diffusion equipment for in vitro permeation studies

Transdermal drug delivery experiments are often tedious and time consuming in terms of sampling, labor, etc. In this way, the automation of such experiments has increased in the last few years. A protocol suitable to validate an automated diffusion equipment with seven in-line flow-through cells is described. The proposed protocol was divided into two parts. First, validation of each component which makes up the whole equipment, including the study of the statistical variability of the internal volumes between the cells, the temperature into the different chambers, the time and sample volumes, etc. In the second part, a series of permeation studies were carried out comparing the performance of the system against a classical Franz-type diffusion cell. Ketoprofen was used as a model drug. It was proved the low variability of the replicates obtained with the automated flow-through diffusion cells. The best work conditions as flow rate into the receptor chamber, temperature, etc., as well as the best mathematical approach for the diffusion data, were determined. The advantages in terms of time saved and easiness of validation of the flow-through cell design in comparison to the Franz-type cell were evidenced.

Influence of pharmacotechnical design on the interaction and availability of norfloxacin in directly compressed tablets with certain antacids

Norfloxacin is a fluorquinolone that can interfere with antacids that contain aluminum and magnesium salts by complexation and modification of its solubility, which reduces its absorption and may lead to therapeutic failures. The purpose of this work was to evaluate the effect of the pharmaceutical design on this interaction and to develop a formulation of norfloxacin tablets in which this process could be avoided. Norfloxacin tablets were designed in 28 formulations. The interaction was studied in terms of in vitro dissolution behavior (USP 23, apparatus 2) in simulated gastric fluid with different doses of four commercially available antacid preparations. It was observed that dissolution rates were markedly reduced in the presence of all antacids studied. This phenomenon was practically avoided with some formulations of norfloxacin tablets in which a disintegrant (sodium starch glycolate or crospovidone) was included. These results indicated that the chelation among metal ions and norfloxacin could be affected by the delivering ability of the drug in the tablet. It was demonstrated that the pharmacotechnical design could modify an interaction process. Some formulations of tablets, in which the reduced dissolution rates in the presence of nonsystemic antacids in vitro was practically avoided, were developed by direct compression.

Validation of a high-performance liquid chromatographic method for the determination of norfloxacin and its application to stability studies (photo-stability study of norfloxacin)

The development and validation study of a sensitive, rapid, reproducible, easy and precise reversed-phase high-performance liquid chromatographic assay for norfloxacin (NFLX) samples from photo-stability of solid dosage forms, without using gradient elution, extraction methods and without using counter-ion has been carried out. The method showed excellent linearity (r2> or =0.999) in the range 1-20 microg ml(-1) using a Lichrosorb-RP-8 column (10 microm, 20 cm x 4.6 mm) and UV-detection (278 nm) at ambient temperature. This method showed good efficiency for the analysis of photodegraded NFLX samples, and was applied to study the photo-stability of NFLX tablets under different conditions (direct sun light, ultraviolet light and fluorescent light). It was proven that the use of a disintegrant can increase the photo-stability of the NFLX in the tablets. This effect was studied in directly compressible tablets with microcrystalline cellulose (MCC) and mannitol for direct compression.

Modification of fluorescent properties of norfloxacin in the presence of certain antacids

Modification of the fluorescent properties of norfloxacin samples in the presence of different antacids in terms of dissolution rates has been reported in a previous paper. The formation of chelates with Al3+ and Mg2+ ions has been previously suggested as a mechanism of interaction. In the present paper, the chelation was studied with different types and amounts of antacids and the stability of the non-absorbable chelates with each antacid was studied. Six dose fractions of each antacid were used in samples with the same norfloxacin concentration (9 microg ml(-1)). All samples were measured using both UV/Vis-spectrophotometry and spectrofluorimetry, and compared to a standard solution of norfloxacin (10 microg ml(-1)) without antacids, used as a reference in the calibration of the spectrofluorimeter. The results showed that the fluorescence signal features remarkable differences depending on the kind and the concentration of antacid, as well as on the time of contact. It was found that increasing amounts of antacids increased the fluorescence signal of norfloxacin samples. The evolution of the fluorescence signal in function of the antacid concentration showed a maximum and a posterior decrease. It was observed that, for a higher concentration of antacid in the medium, a higher signal was obtained and lower stability of the compound norfloxacin-antacid was observed. The data obtained strongly indicated that the binding of Al3+ and Mg2+ ions to the carboxylic groups of norfloxacin produced non-absorbable chelates. This effect might reduce the drug bioavailability.

The effect of photodegradation on the fluorescent properties of norfloxacin: (photodegradation and fluorescence of norfloxacin)

Norfloxacin (NFLX), a broad spectrum antibacterial quinolone, is a very thermostable but photosensitive drug, especially in solution leading to the formation of an ethylenediamine degradate. The modification of the fluorescent properties of NFLX in acid solution after exposure to fluorescent light and the degradation mechanisms were studied. Two analytical methods were previously developed and validated for NFLX, ultraviolet spectrophotometry (UV) and spectrofluorimetry (FL). Data obtained using both methods in the analysis of remaining NFLX in terms of percent recoveries revealed that there was no statistically significant modifications of the UV signal and of the recoveries obtained by the method. However, an important increase of the fluorescent signal after light exposure of NFLX solutions appeared, which led to an increase of the average recovery up to 270% over 15 months. Using a previously validated HPLC method for the photostability studies of NFLX, a loss of 5% with respect to the initial drug amount was observed. The study of UV and fluorescence spectra evidenced the formation of the degradation product, which induced significant modification of the fluorescent properties of NFLX samples. These results clearly indicated that FL analysis definitively is the method of choice and can be used to study the photodegradation of NFLX.

Determination of norfloxacin by fluorescence in the presence of different antacids: quantification of analytical interferences

Norfloxacin is a fluorquinolone that can interfere with certain antacids (derivatives of Al and Mg) because its dissolution profiles are dependent on pH. Furthermore, it can form insoluble complexes that modify its absorption and bioavailability. Two sensitive and selective analytical methods using fluorescence (FL) and UV spectrophotometry (UV) have been developed to study the dissolution behaviour in gastric juice of different formulations of norfloxacin in tablets. There are no significant differences when the samples are measured by both methods and their ruggedness in the presence of some excipients is proven. From this, it is concluded that they are effective for this study. When different antacids are added to the dissolution medium, using UV and FL methods with the same samples, totally different dissolution profiles appear. Using FL, it would appear that up to 400% of the amount of norfloxacin in the tablet is released. These profiles are misleading because the uniformity of dosage units was tested before the dissolution studies. It is proven that the antacids dissolved in gastric juice do not produce fluorescence, but cause important analytical interferences with norfloxacin. This may be because their association with Al3+ or Mg2+ forms a new compound. Nevertheless, it is observed that this effect is more important in some antacids (Almagate, Magaldrate). This may be because their ability to deliver Al to the medium is greater.