Exquisite integration of quality-by-design and green analytical approaches for simultaneous determination of xylometazoline and antazoline in eye drops and rabbit aqueous humor, application to stability study

This work implements a stability indicating HPLC method developed to simultaneously determine xylometazoline (XYLO) and antazoline (ANT) in their binary mixture, rabbit aqueous humor and cited drug's degradates by applying analytical quality-by-design (AQbD) combined with green analytical chemistry (GAC) experiment for the first time. This integration was designed to maximize efficiency and minimize environmental impacts, as well as energy and solvent consumption. Analytical quality-by-design was applied to achieve our aim starting with evaluation of quality risk and scouting analysis, tracked via five parameters chromatographic screening using Placket-Burman design namely: pH, temperature, organic solvent percentage, flow rate, and wavelength detection. Recognizing the critical method parameters was done followed by optimization employing central composite design and Derringer's desirability toward assess optimum conditions that attained best resolution with satisfactory peak symmetry with short run time. Optimal chromatographic separation was attained by means of an XBridge® C18 (4.6 × 250 mm, 5 µm) column through isocratic elution using a mobile phase consists of phosphate buffer (pH 3.0): ethanol (60:40, by volume) at a 1.6 mL/min flow rate and 230.0 nm UV detection. Linearity acquired over a concentration range of 1.0-100.0 µg/mL and 0.5-100.0 µg/mL for XYLO and ANT, respectively. Furthermore, imperiling cited drugs' stock solutions to stress various conditions and satisfactory peaks of degradation products were obtained indicating that cited drugs are vulnerable to oxidative degradation and basic hydrolysis. Degradates' structures were elucidated using mass spectrometry. Applying various assessment tools; namely: analytical greenness (AGREE), green analytical procedure index (GAPI), analytical eco-scale, and national environmental method index (NEMI), Greenness method's evaluation was applied and proved to be green. In fact, the developed method is established to be perceptive, accurate, and selective to assess cited drugs for routine analysis.

Selective and Sensitive Chromatographic Methods for Determination of a Co-Formulated Binary Mixture in Antibacterial Eye Drops and Aqueous Humor in the Presence of Their Degradation Products and Potential Impurities

Prednisolone acetate (PDN) is a corticosteroid anti-inflammatory liable to degradation under different conditions and used with antibiotics in eye drops. Two selective stability-indicating separation techniques were developed for simultaneous determination of PDN and moxifloxacin HCl (MXF) binary mixture in pure forms, ophthalmic formulation, in the presence of PDN impurities and in the presence of their degradation products. The first method was based on HPTLC separation using silica gel 60 F254 HPTLC plates, and a developing system of toluene: ethyl acetate: methanol: ammonia (5.0: 6: 2.0: 0.05, v/v/v/v) is used with detection at 254 nm. The second method was HPLC using a mobile phase of acetonitrile: methanol: deionized water, pH 2.8 (25.0: 35.0: 40.0, v/v/v), at 254 nm. A kinetic study utilizing the developed HPLC method for PDN degradation under different stress conditions was performed. Furthermore, the method was applied for determination in rabbit aqueous humor. Validation was conducted as per ICH guidelines, and system suitability was ascertained. The calibration curves were constructed in the range 0.10-25.00 and 0.20-50.00 μg band-1, for PDN and MXF by HPTLC, while for HPLC, it was 0.02-50.00 and 0.10-50.00 μg mL-1 for both drugs, in order.

Microbial safety implications of in-use topical diagnostic ophthalmic medications in eye clinics in Ghana

PURPOSE

To determine the microbial contaminants and its clinical importance in topical diagnostic ophthalmic medications (cycloplegics/mydriatics and miotics) in eye clinics in Ghana.

METHOD

A cross-section of eye clinics was sampled for the diagnostic agents (Atropine, Phenylephrine, Tropicamide and Cyclopentolate, Pilocarpine). Standard laboratory procedures and protocols were observed in culturing the samples on different Agars. Microscopy and various biochemical tests were performed to identify microbial species. Antimicrobial susceptibility testing was also performed to ascertain the clinical importance of the isolated microbes.

RESULTS

A total of 113 samples were obtained, from which 334 bacteria were isolated which included Bacilli spp. 91(27.25%), Coagulase Negative Staphylococci spp. 59(17.66%), Moraxella spp. 47(14.07%), Staphylococcus aureus 41(12.27%), Streptococcus spp. 21(6.29%), Klebsiella spp. 20(5.99%), Pseudomonas spp. 13(3.89%), Proteus spp. 12(3.59%), Escherichia coli. 12 (3.59%), Serratia spp. 10(2.99%), Shigella spp. 7(2.09%), Salmonella spp. 1(0.3%). There were 96 isolated fungal contaminants mainly Penicillium spp. 41(42.71%), Cephalosporium spp. 19(19.79%), Cladosporium spp. 15(15.63%), Aspergillus spp. 13(13.54%), Cercospora spp. 8(8.33%). The diagnostic agent with the most bacteria contamination was Phenylephrine 90 (26.95%) and the least being Pilocarpine 49 (14.67%). Also, the diagnostic agent with the most fungal contamination was Cyclopentolate 29 (30.2%) and the least was Tropicamide and Pilocarpine with 15 (15.63%) each. Gentamicin and Ciprofloxacin were the only antibiotics that showed 100% activity against all the bacterial isolates. Fungal contaminants were more susceptible to Ketoconazole as compared to Fluconazole.

CONCLUSION

Topical diagnostic ophthalmic preparations used in clinical settings in Ghana are contaminated with clinically important bacteria and fungi.

Measurement of Free Iodine in Different Formulations of Povidone-Iodine Eye Drops 5

There are multiple studies in the literature that support the use of povidone iodine in the preparation of the surgical field of cataract as the most effective means to reduce the bacteria present in the ocular surface and the risk of infection. The concentration of free iodine is related to the antiseptic activity of these compounds, being, therefore, a good indicator of its effectiveness. The objective of this study was to determine the amount of free iodine and the evolution of it in different formulations of povidone iodine eye drops. The povidone iodine 5% eye drops were prepared starting from Betadine 10% dermal or the active principle and using a solvent, phosphate-citrate buffer solution, and sodium chloride 0.9% or sterile water for injection. Aliquots of 5 mL were packed in low-absorption absorption eye drops, topaz glass vials, and polyethylene syringe. The determination of free iodine was made by volumetric titration. Titration was performed with 0.1 M sodium thiosulfate using a starch solution as an indicator. Of the 0.1 M sodium thiosulfate, 1 mL is equivalent to 12.69 mg of available iodine, and it is expressed as a percentage of free iodine in the iodized povidone (% free iodine). Eyewash titrations were performed by replacing the substance with 5 mL of eye drops and following the remaining steps. Valuations were made on days 0, 7, and 14, as well as the measurement of pH and osmolarity. The results show that there are no differences between the average results at the three measurements taken on days 0, 7, and 14. We conclude that the free iodine remains stable during the stability period of 14 days. Regarding the pH and osmolarity data, the authors believe that the best tolerated formula will be that elaborated with povidone iodine and a phosphate- citrate buffer solution.

HPLC-UV method for simultaneous determination of sparfloxacin and dexamethasone sodium phosphate in eye drops

A simple, sensitive liquid chromatographic method was developed and validated for the simultaneous estimation of sparfloxacin and dexamethasone sodium phosphate in bulk and pharmaceutical formulations. Optimum separation was achieved in less than 10 min using a C18 column (250 mmx4.6 mm i.d, 5μ particle size) by isocratic elution. The mobile phase consisting of a mixture of mixed phosphate buffer (pH 6.8) and acetonitrile (50:50, v/v) was used. Column effluents were monitored at 224nm at a flow rate of 1ml/min. Retention times of sparfloxacin and dexamethasone sodium phosphate were 3.01 and 6.47 min respectively. The linearity of sparfloxacin and dexamethasone sodium phosphate was in the range of 3-18μg/ml and 1-6μg/ml respectively. Developed method was economical because, the time taken and amount of solvent consumed for each analysis was less. The method was validated and was applied to the simultaneous determination of sparfloxacin and dexamethasone sodium phosphate in bulk and pharmaceutical formulations.

Galenic validation of plasma rich in growth factors eye drops

OBJECTIVE

Galenic evaluation of the process for obtaining and storing the platelet rich in growth factors PRGF-Endoret® eye drops.

METHOD

To assess whether the PRGF-Endoret® eye drops process is aseptically obtained, a sterility test was carried out on the eye drops; the tightness of the PRGF-Endoret® eye drops containers was also analyzed. Likewise, the chemical and biological properties of the PRGF- Endoret® eye drops were evaluated after the obtaining process and storage.  Eye drop filtration tests, one cycle of freezing at -20 °C and thawing, and  eye drop stability for three and six months stored at -20 °C were included.

RESULTS

The results obtained in the sterility test showed no microbial  contamination in any of the analyzed eyedropper; tightness test showed that  100% of the eyedrop containers and the 98.4% of the plugs analyzed  remained hermetic. On the other hand, all the growth factors measured  remained constant after filtering the PRGF-Endoret® eye drops.  Furthermore, the different eye drop stability tests carried out in this study  showed no significant changes in the growth factors levels, cell proliferative  activity or in the chemical characteristics analyzed. Conclusions: The PRGF-Endoret® eye drops are obtained in a safety and aseptic manner following the guidelines issued by the Spanish Agency  for Drugs and Health Products and the Ministry of Health to obtain medicines for human use. The PRGF-Endoret® eye drops maintain their physical-chemical and biological properties after being subjected to different  storage times and temperatures.

Investigation of the spectrofluorimetric behavior of azelastine and nepafenac: Determination in ophthalmic dosage forms

The first spectrofluorimetric report investigating the fluorimetric behavior of the antihistaminic drug, azelastine (AZEL), and the non-steroidal anti-inflammatory drug, nepafenac (NEP), either in bulk or in their dosage forms, eye drops and ophthalmic suspension. After a full investigation of the factors that may influence their spectrofluorimetric behavior: pH, different organized media and organic solvents, the optimum factors were set in order to enable the analysis of each drug with maximum sensitivity. The AZEL spectrofluorimetric analysis was set at 286/364 (λ_ex/λ_em) in distilled water while for NEP, the analysis was set at 228/303 (λ_ex/λ_em) in methanol. The linearity range for AZEL was from 0.1 to 1.5 μg/mL while that of NEP was from 0.2 to 1.5 μg/mL. The linearity yielded good regression parameters with low LOD (0.022 and 0.032 μg/mL for AZEL and NEP, respectively) and LOQ (0.073 and 1.08 μg/mL for AZEL and NEP, respectively) when compared with those obtained from many previous spectroscopic and chromatographic reports in literature. The method was ICH validated and was applied to the analysis of AZEL and NEP with good selectivity regarding the inactive ingredients.

Chemical and toxicological studies on different brands of Asmad (Antimony sulphide) available in Pakistan and Saudi Arabia

Eye is the most beautiful, important and sensitive organ of human body. It is not only linked with visionary complex optical system also has the ability to differentiate among the millions of colors. The apparent human personality is also associated with it. Asmad/Antimony Sulfide/Kohl/Surma powder is one of the eye preparation has been used since ancient time. There are several aesthetic and ophthalmic preparations available for human eye and they have closed association between the aesthetic and medicinal significance such as cleansing, soothing, strengthening and anti-infectious actions along with beautifying purpose of eye. The main objective of present research is to provide scientific findings regarding beneficial and toxic effects of Asmad products available in market for the frequent users. The chemical and toxicological investigations on ten selected famous brands of Pakistan samples (PHS1, PHS2, PLS, PMS and PSS) and Saudi Arabia samples (SBS, SAS, SHS, SMS and STS) were carried out through advanced and sophisticated technique Scanning Electron Microscope (SEM) linked with Energy Dispersive X-ray Spectroscopy (EDS) which is used to determine the presence different percentages of organic and inorganic elements in all the brands of Pakistani and Saudi Arabian samples. The safety and toxicity depends on the Na, Mg, Ca, K, Al, Cu, Zn, Fe, Bi, Si, O, C, S and Pb percentages respectively of the Asmad products.

The application of artificial neural networks and support vector regression for simultaneous spectrophotometric determination of commercial eye drop contents

In the present study, artificial neural networks (ANNs) and support vector regression (SVR) as intelligent methods coupled with UV spectroscopy for simultaneous quantitative determination of Dorzolamide (DOR) and Timolol (TIM) in eye drop. Several synthetic mixtures were analyzed for validating the proposed methods. At first, neural network time series, which one type of network from the artificial neural network was employed and its efficiency was evaluated. Afterwards, the radial basis network was applied as another neural network. Results showed that the performance of this method is suitable for predicting. Finally, support vector regression was proposed to construct the Zilomole prediction model. Also, root mean square error (RMSE) and mean recovery (%) were calculated for SVR method. Moreover, the proposed methods were compared to the high-performance liquid chromatography (HPLC) as a reference method. One way analysis of variance (ANOVA) test at the 95% confidence level applied to the comparison results of suggested and reference methods that there were no significant differences between them. Also, the effect of interferences was investigated in spike solutions.

New Electrochemically-Modified Carbon Paste Inclusion β-Cyclodextrin and Carbon Nanotubes Sensors for Quantification of Dorzolamide Hydrochloride

The present article introduces a new approach to fabricate carbon paste sensors, including carbon paste, modified carbon paste inclusion β-cyclodextrin, and carbon nanotubes for the quantification of dorzolamide hydrochloride (DRZ). This study is mainly based on the construction of three different carbon paste sensors by the incorporation of DRZ with phosphotungstic acid (PTA) to form dorzolamide-phosphotungstate (DRZ-PT) as an electroactive material in the presence of the solvent mediator ortho-nitrophenyloctyl ether (o-NPOE). The fabricated conventional carbon paste sensor (sensor I), as well as the other modified carbon paste sensors using β-cyclodextrin (sensor II) and carbon nanotubes (sensor III), have been investigated. The sensors displayed Nernstian responses of 55.4 ± 0.6, 56.4 ± 0.4 and 58.1 ± 0.2 mV·decade⁻¹ over concentration ranges of 1.0 × 10⁻⁵–1.0 × 10⁻², 1.0 × 10⁻⁶–1.0 × 10⁻², and 5.0 × 10⁻⁸–1.0 × 10⁻² mol·L⁻¹ with lower detection limits of 5.0 × 10⁻⁶, 5.0 × 10⁻⁷, and 2.5 × 10⁻⁹ mol·L⁻¹ for sensors I, II, and III, respectively. The critical performance of the developed sensors was checked with respect to the effect of various parameters, including pH, selectivity, response time, linear concentration relationship, lifespan, etc. Method validation was applied according to the international conference on harmonisation of technical requirements for registration of pharmaceuticals for human use ICH guidelines. The developed sensors were employed for the determination of DRZ in its bulk and dosage forms, as well as bio-samples. The observed data were statistically analyzed and compared with those obtained from other published methods.

Comparative study of novel versus conventional two-wavelength spectrophotometric methods for analysis of spectrally overlapping binary mixture

Smart spectrophotometric methods have been applied and validated for the simultaneous determination of a binary mixture of chloramphenicol (CPL) and prednisolone acetate (PA) without preliminary separation. Two novel methods have been developed; the first method depends upon advanced absorbance subtraction (AAS), while the other method relies on advanced amplitude modulation (AAM); in addition to the well established dual wavelength (DW), ratio difference (RD) and constant center coupled with spectrum subtraction (CC-SS) methods. Accuracy, precision and linearity ranges of these methods were determined. Moreover, selectivity was assessed by analyzing synthetic mixtures of both drugs. The proposed methods were successfully applied to the assay of drugs in their pharmaceutical formulations. No interference was observed from common additives and the validity of the methods was tested. The obtained results have been statistically compared to that of official spectrophotometric methods to give a conclusion that there is no significant difference between the proposed methods and the official ones with respect to accuracy and precision.

Novel spectrophotometric determination of chloramphenicol and dexamethasone in the presence of non labeled interfering substances using univariate methods and multivariate regression model updating

Smart and novel spectrophotometric and chemometric methods have been developed and validated for the simultaneous determination of a binary mixture of chloramphenicol (CPL) and dexamethasone sodium phosphate (DSP) in presence of interfering substances without prior separation. The first method depends upon derivative subtraction coupled with constant multiplication. The second one is ratio difference method at optimum wavelengths which were selected after applying derivative transformation method via multiplying by a decoding spectrum in order to cancel the contribution of non labeled interfering substances. The third method relies on partial least squares with regression model updating. They are so simple that they do not require any preliminary separation steps. Accuracy, precision and linearity ranges of these methods were determined. Moreover, specificity was assessed by analyzing synthetic mixtures of both drugs. The proposed methods were successfully applied for analysis of both drugs in their pharmaceutical formulation. The obtained results have been statistically compared to that of an official spectrophotometric method to give a conclusion that there is no significant difference between the proposed methods and the official ones with respect to accuracy and precision.

A comparative study of different aspects of manipulating ratio spectra applied for ternary mixtures: derivative spectrophotometry versus wavelet transform

This work represents a comparative study of different aspects of manipulating ratio spectra, which are: double divisor ratio spectra derivative (DR-DD), area under curve of derivative ratio (DR-AUC) and its novel approach, namely area under the curve correction method (AUCCM) applied for overlapped spectra; successive derivative of ratio spectra (SDR) and continuous wavelet transform (CWT) methods. The proposed methods represent different aspects of manipulating ratio spectra of the ternary mixture of Ofloxacin (OFX), Prednisolone acetate (PA) and Tetryzoline HCl (TZH) combined in eye drops in the presence of benzalkonium chloride as a preservative. The proposed methods were checked using laboratory-prepared mixtures and were successfully applied for the analysis of pharmaceutical formulation containing the cited drugs. The proposed methods were validated according to the ICH guidelines. A comparative study was conducted between those methods regarding simplicity, limitation and sensitivity. The obtained results were statistically compared with those obtained from the reported HPLC method, showing no significant difference with respect to accuracy and precision.

[Eye-drops from olden times to the XIXth century]

The Spanish word "colirio" comes from the Latin collyrium, which in turn came from the Greek kollirion. Initially, the Romans use this word in a general way, but due to their use mainly in ophthalmology, the use of the term became restricted to those topical medications destined for the care and prevention of ocular diseases, from solutions and suspensions to poultices, salves and ointments. During the Middle Ages "colirio" included not only substances used to dilate ladies' pupils for aesthetic reasons but also medications for ocular hygiene and treatment. The Industrial Revolution of the XIXth century barely modified ophthalmic pharmaceutical technology. It is only since the World War II that the preparation of eye-drops has undergone a rapid development and improvement, adopting the concept of sterility as a necessary condition for all ophthalmic solutions and taking very precise rules for their elaboration and conditioning from different pharmacopeia.

[Determination of enantiomeric impurity of timolol maleate in bulk substances and eye drops]

OBJECTIVE

To determine the enantiomeric impurity contents of domestic timolol maleate in bulk drugs and eye drops.

METHODS

Enantiomer impurity of timolol was assayed by chiral high performance liquid chromatography. The chromatographic conditions were as follows:chiralcel OD chiral column (4.6 mm ×150 mm, 5μm), detection wavelength:297 nm, mobile phase:hexane-isopropanol-diethylamine (480:20:1), column temperature:25 ℃, flow rate:1.0 ml/min, sample injection volume:5 μl.

RESULTS

The resolution between R- and S-timolol was more than 4. The enantiomeric impurity contents were less than 0.67% on average in two batches of timolol maleate bulk drugs, and 0.31% on average in three batches of timolol maleate eye drops.

CONCLUSION

Enantiomeric impurity contents in each batch of products all meet European Pharmacopoeia criteria, which can be used as references in Chinese Pharmacopoeia criteria.

Collyria seals in the Roman Empire

Roman seals associated with collyria (Latin expression for eye drops/washes and lotions for eye maintenance) provide valuable information about eye care in the antiquity. These small, usually stone-made pieces bore engravings with the names of eye doctors and also the collyria used to treat an eye disease. The collyria seals have been found all over the Roman empire and Celtic territories in particular and were usually associated with military camps. In Hispania (Iberian Peninsula), only three collyria seals have been found. These findings speak about eye care in this ancient Roman province as well as about of the life of the time. This article takes a look at the utility and social significance of the collyria seals and seeks to give an insight in the ophthalmological practice of in the Roman Empire.

[Counterfeiting of eye drops?: a laboratory study of antibiotic eye drops purchased in two African countries]

INTRODUCTION

Counterfeit drugs are often ineffective and are considered a problem with an immense risk potential especially in the treatment of infectious diseases. Emerging and developing countries are particularly affected. Little is known about the extent of counterfeit antibiotic drugs used in eye care. In the present study we investigated antibiotic eye drops purchased in two African countries with respect to the active substance and its concentration in the sample.

METHODS

A total of 33 antibiotic eye drops purchased in Kenya and the Democratic Republic of Congo were tested. The bottles were labeled to contain one of the following substances: the quinolones ciprofloxacin, levofloxacin and ofloxacin and the aminoglycosides gentamicin and tobramycin. Imported quality products as well as cheaper generic drugs were tested. Fluoroquinolones were determined by high pressure liquid chromatography (HPLC) and quantified by fluorescence measurement and aminoglycosides were tested by using a fluorescence polarization immunoassay.

RESULTS

All samples were found to contain the declared drug. Nine samples (27%) showed an under-concentration by 10% or less and ten (30%) showed an increased concentration of 10% or more than indicated on the label. 75% of the original drugs but only 12% of the generic drugs had measured concentrations within the standard advisory ranges of ± 5% from the nominal value.

CONCLUSION

Our results provide no evidence for significant criminal counterfeiting of eye drops in the studied countries. The frequent deviation from the stated concentration in the generic samples is cause for concern and justifies further investigation.

Combining the isoabsorptive point in the ratio spectrum and the smart ratio difference methods for a single step determination of compounds with overlapped spectra

A new method significantly advantageous over the conventional spectrophotometric methods regarding simplicity, minimal data processing and applicability was developed. The new method is based on the fact that isoabsorptive points whenever present in an absorption spectrum will be retained even after division by a one component as a divisor in the ratio spectrum, in addition to a smart modification of the conventional ratio derivative and ratio subtraction methods. This modified method though simpler, enabled wider range of applications. The proposed method was applied for the analysis of brimonidine and timolol in laboratory prepared mixtures with mean percentage recoveries 100.64 ± 1.10 and 100.96 ± 1.16, respectively, and in their pharmaceutical formulation with mean percentage recoveries 100.88 ± 0.34 and 100.84 ± 0.72, respectively. The suggested method was validated according to USP guidelines and can be applied for routine analysis in quality control laboratories.

Simultaneous determination of antazoline and naphazoline by the net analyte signal standard addition method and spectrophotometric technique

A novel net analyte signal standard addition method (NASSAM) was used for simultaneous determination of the drugs anthazoline and naphazoline. The NASSAM can be applied for determination of analytes in the presence of known interferents. The proposed method is used to eliminate the calibration and prediction steps of multivariate calibration methods; the determination is carried out in a single step for each analyte. The accuracy of the predictions against the H-point standard addition method is independent of the shape of the analyte and interferent spectra. The net analyte signal concept was also used to calculate multivariate analytical figures of merit, such as LOD, selectivity, and sensitivity. The method was successfully applied to the simultaneous determination of anthazoline and naphazoline in a commercial eye drop sample.

Anaphylactic reaction due to cyclopentolate in a 4-year-old child

Ophthalmologists frequently use mydriatics both for diagnosis (retinal exploration, refraction tests) and for treatment. Cyclopentolate is used to induce quick and successful mydriasis for pediatric eye examination. Hypersensitivity reaction to cyclopentolate is very uncommon, especially in children. We report the case of a child who experienced a hypersensitivity reaction to cyclopentolate during preparation for an eye examination under cycloplegia.

Determination of atropine enantiomers in ophthalmic solutions by liquid chromatography using a Chiral AGP column

Many therapeutic agents are commercialized under their racemic form. The enantiomers can show differences in the pharmacokinetic and pharmacodynamic profile. The use of a pure enantiomer in pharmaceutical formulations may result in a better therapeutic index and fewer adverse effects. Atropine, an alkaloid of Atropa belladonna, is a racemic mixture of l-hyoscyamine and d-hyoscyamine. It is widely used to dilate the pupil. To quantify these enantiomers in ophthalmic solutions, an HPLC method was developed and validated using a Chiral AGP column at 20 degrees C. The mobile phase consisted of a buffered phosphate solution (containing 10 mM 1-octanesulfonic acid sodium salt and 7.5 mM triethylamine, adjusted to pH 7.0 with orthophosphoric acid) and acetonitrile (99 + 1, v/v). The flow rate was 0.6 ml/min, with UV detection at 205 nm. In the concentration range of 14.0-26.0 microg/mL, the method was found to be linear (r > 0.9999), accurate (with recovery of 100.1-100.5%), and precise (RSD system < or = 0.6%; RSD intraday < or = 1.1%; RSD interday < or = 0.9%). The method was specific, and the standard and sample solutions were stable for up to 72 h. The factorial design assures robustness with a variation of +/- 10% in the mobile phase components and 2 degrees C of column temperature. The complete validation, including stress testing and factorial design, was studied and is presented in this research.

[Nanosilver sensitized fluorescence and second-order scattering of Tb (III)-norfloxacin and its application]

Norfloxacin (NFLX) can form complex with Tb(III) ion, and the intramolecular energy transfer from NFLX to Tb (III) takes place when excited. And thus the characteristic fluorescence of Tb (III) ion is enhanced and the maximum fluorescence peak locates at 545 nm. The second-order scattering (SOS) peak at 545 nm also appears for the Tb (III)-NFLX complex with the excitation wavelength of 272 rnm. When the silver nanoparticles were added to the Tb (III)-NFLX binary system, the luminescence intensity at 545 nm greatly increased. And the relative intensity is proportional to the amount of NFLX. Based on this phenomenon, a novel method for the determination of NFLX has been developed by using a common spectrofluorometer to measure the intensity of fluorescence and SOS. The calibration graphs for NFLX are linear in the range of 6.0 x 10(-9)-1.0 x 10(-5) mol x L(-1), and the detection limit is 4.4 x 10(-9) x mol x L(-1). This method was applied satisfactorily to the determination o f NFLX in capsule and eye drop samples. The experimental results showed that it is the certain size and certain concentration of silver nanoparticles that can greatly enhance the fluorescence-SOS intensity.

Evaluation of monolithic HPLC columns for various pharmaceutical separations: Method transfer from conventional phases and batch to batch repeatability

Methods developed on conventional particle-packed C18 columns for pilocarpine, propranolol, glibenclamide, glimepiride, insulin and their respective degradation products or related compounds were transferred from the conventional Superspher 100RP-18e column to Chromolith Performance RP-18e columns. All transfers were successful applying the same chromatographic conditions, except for insulin where the acetonitrile content of the mobile phase was reduced by 0.5%. The intraday and interday precisions for both retention time and peak area were evaluated over a wide concentration range. Results were found to be equal, or slightly better on Chromolith Performance with RSD%<1.1% in all cases. Monolithic batch to batch repeatability of both retention time and peak area, compared for monolithic columns from different batches gave an RSD% of less than 1.3%. The separation of each drug and its related products was investigated on monolithic columns at flow rates from 1 to 9 ml/min, and superior resolution was always obtained using monolithic over conventional columns at the same flow rate. A total of seven monolithic columns from four different batches were used in this study.

A Simple Flow-injection Spectrofluorimetric Method for the Determination of Mercury

A highly sensitive flow-injection spectrofluorimetric method is presented for the rapid and simple determination of Hg (II) in environmental and pharmaceutical samples. Murexide (ammonium purpurate) was used as the fluorescence reagent in the carrier stream. An emission peak of murexide, which is decreased linearly by addition of Hg (II), occurs at 435 nm in aqueous solution with excitation at 335 nm. A linear calibration was obtained for 5-200 ng ml(-1) Hg (II) with the relative standard deviation 2.5% (n = 5) for a 20 microl injection volume Hg (II). The limit of the detection was 1 ng ml(-1) and the sampling rate was 80 h(-1). No significant interference was found by the ions commonly found in the most environmental samples. The proposed method was successfully applied for the determination of trace mercury in real samples and the validation of the proposed methodology is provided.

NMR analysis of ion pair formation between timolol and sorbic acid in ophthalmic preparations

Ion pair formation between timolol and sorbic acid was investigated using NMR spectroscopy in order to clarify their interactions within ophthalmic preparation. (13)C and (1)H NMR spectra of timolol, sorbic acid, and a mixture of the two were obtained, and the signal changes induced by pairing were observed. The carbon signals of the butylaminopropanol moiety of timolol were markedly shifted in the mixture, as were the carboxyl and conjugated carbons assigned to sorbic acid. The localizations of the changes in each molecule revealed the binding sites. The profiles of butylaminopropanol carbon chemical shifts plotted against a molar ratio of sorbate were synchronized, which suggested a single type of interaction with sorbic acid. The Job plot showed a typical pattern with a single-maximum at a mole function of 0.5, indicating the presence of a 1:1 complex of timolol and sorbic acid. The stability constants (K) of the timolol-sorbate and timolol-maleate pairs were 1.9x10(1) and 2.2x10(2)M(-1), respectively. The higher K value of the timolol-maleate interaction suggested that it was dominant to the timolol-sorbate interaction when maleate and sorbate coexisted within a timolol solution. Here, we demonstrated evidence of an interaction between timolol and sorbic acid using simple NMR measurements, which suggested the existence of ion pair formation derived from charge neutralization. Our analysis using NMR spectroscopy should advance the understanding and optimization of formulations that are based on ion pair.

Analysis of benzalkonium chloride by capillary electrophoresis-tandem mass spectrometry

Conditions for the separation and determination of benzalkonium chloride (BAC) homologues by CE with UV-detection and CE coupled to MS (IT) using electrospray as ionization source were established. The separation was performed using fused-silica capillaries of 50 microm id and 100 mM acetic acid-ammonium acetate buffer solution at pH 4.5 with 80% of ACN as carrier electrolyte. CE-MS coupling parameters were optimized and methanol-10 mM acetic acid (90:10 v/v) was selected as sheath liquid. Detection limits, based on an S/N of 3:1, were calculated, and values between 0.8 and 1.3 mg/L with CE-ESI/MS and around 0.5 mg/L with CE-ESI-MS/MS, using hydrodynamic injection (15 s, 3.5 kPa), were obtained. Good run-to-run and day-to-day precisions on concentration were achieved with RSDs lower than 8%. Quantitative analysis was carried out by the internal standard method and the calibration curves showed good linearities (r(2) > 0.98). The CE-ESI-MS/MS method was successfully applied to the analysis of BAC in different ophthalmic solutions, allowing the direct determination, identification and confirmation of the BAC homologues presented in these samples.

A rapid derivative spectrophotometric method for simultaneous determination of naphazoline and antazoline in eye drops

A zero-crossing first-derivative spectrophotometric method is applied for the simultaneous determination of naphazoline hydrochloride and antazoline phosphate in eye drops. The measurements were carried out at wavelengths of 225 and 252 nm for naphazoline hydrochloride and antazoline phosphate, respectively. The method was found to be linear (r2>0.999) in the range of 0.2-1 microg/ml for naphazoline hydrochloride in the presence of 5 microg/ml antazoline phosphate at 225 nm. The same linear correlation (r2>0.999) was obtained in the range of 1-10 microg/ml of antazoline phosphate in the presence of 0.5 microg/ml of naphazoline hydrochloride at 252 nm. The limit of determination was 0.2 microg/ml and 1 microg/ml for naphazoline hydrochloride and antazoline phosphate, respectively. The method was successfully used for simultaneous analysis of naphazoline hydrochloride and antazoline phosphate in eye drops without any interference from excipients and prior separation before analysis.

Concentration of latanoprost ophthalmic solution after 4 to 6 weeks' use in an eye clinic setting

PURPOSE

To determine the concentration of latanoprost in bottles of latanoprost ophthalmic solution 0.005% after 4 or 6 weeks of use in patients in an eye clinic setting.

METHODS

Patients treated with latanoprost for open-angle glaucoma or ocular hypertension were randomly assigned to refill their prescriptions either at the Doheny Eye Institute clinic or a local pharmacy. Patients who used latanoprost binocularly were asked to return bottles to the clinic after 4 weeks of use and nonrefrigerated storage, and those who used latanoprost monocularly were asked to return used bottles after 6 weeks. Patients were then interviewed to determine bottle storage information and doses missed. Latanoprost concentration in residual solution was analyzed in a masked fashion, by reversed-phase high-performance liquid chromatography (HPLC).

RESULTS

In all, 110 patients were enrolled and 89 returned their bottles. Sixty-nine bottles had sufficient residual volume to conduct HPLC analysis. All patients reported that bottles were stored at room temperature (average high from 70-95 degrees F during the daytime). The mean +/- SD latanoprost concentration measured in the residual solutions was 48.31 +/- 2.31 microg/mL. Ninety-four percent of the bottles had concentrations within 90% to 110% of the labeled amount. No difference in latanoprost concentrations was found between the bottles used for 4 weeks versus those used for 6 weeks.

CONCLUSIONS

In an eye clinic setting, latanoprost ophthalmic solution 0.005% remains stable after 4 or 6 weeks of patient use from the same bottle when stored at room temperature.

Desorption Electrospray Ionization Mass Spectrometry for High-Throughput Analysis of Pharmaceutical Samples in the Ambient Environment

Desorption electrospray ionization (DESI) allows mass spectrometry to be used for on-line high-throughput monitoring of pharmaceutical samples in the ambient environment, without prior sample preparation. Positive and negative ion DESI are used to characterize the active ingredients in pharmaceutical samples formulated as tablets, ointments, and liquids. Compounds of a wide variety of chemical types are detected in these complex matrices. The effects on analytical performance of operating parameters, including the electrospray high voltage, heated capillary temperature, solvent infusion rate, and solvent composition, are evaluated and optimized. In addition to experiments in which a simple solvent is sprayed onto the solid analyte samples, reactive desorption is performed by adding reagents to the solvent spray to generate particularly stable or characteristic ions with the analytes of interest. A variable-speed moving belt was built for high-throughput sampling and used to provide rapid qualitative and semiquantitative information on drug constituents in tablets. Sampling rates as high as 3 samples/s are achieved in the ambient environment. Relative standard deviations of the relative ion abundances for major components in the mass spectra are in the range of 2-8%. Impurities and components present at levels as low as approximately 0.1% are identified and carryover effects are minimized in high-throughput on-line analysis of pharmaceutical samples.

New, simple and validated UV-spectrophotometric methods for the estimation of gatifloxacin in bulk and formulations

New, simple and cost effective UV-spectrophotometric methods were developed for the estimation of gatifloxacin in bulk and pharmaceutical formulations. Gatifloxacin was estimated at 286 nm in 100 mM phosphate buffer (pH 7.4) and 292 nm in 100 mM hydrochloric acid (pH 1.2). Linearity range was found to be 1-18 mug ml(-1) (regression equation: absorbance=0.0684 x Concentration in microg ml(-1) + 0.0050; r2 = 0.9998) in the phosphate buffer (pH 7.4) and 1-14 microg ml(-1) (regression equation: absorbance = 0.0864 x Concentration in microg ml(-1) + 0.0027; r2 = 0.9999) in hydrochloric acid medium (pH 1.2). The apparent molar absorptivity was found to be 2.62 x 10(4) l mol(-1) cm(-1) in the phosphate buffer and 3.25 x 10(4) l mol(-1) cm(-1) in hydrochloric acid media. In both the proposed methods sandell's sensitivity was found to be about 0.01 microg cm(-2)/0.001A. These methods were tested and validated for various parameters according to ICH guidelines and USP. The quantitation limits were found to be 0.312 and 0.3 microg ml(-1) in the phosphate buffer and hydrochloric acid medium, respectively. The proposed methods were successfully applied for the determination of gatifloxacin in pharmaceutical formulations (tablets, injection and ophthalmic solution). The results demonstrated that the procedure is accurate, precise and reproducible (relative standard deviation <2%), while being simple, cheap and less time consuming and can be suitably applied for the estimation of gatifloxacin in different dosage forms and dissolution studies.

Examination of Purification Methods and Development of Intravitreal Injection of Triamcinolone Acetonide

PURPOSE

Intravitreal injection of triamcinolone acetonide (TA) is used in ophthalmic treatment, but the reliability of commercially available TA preparations has still not been established. We evaluated two previously reported purification methods, and developed a more reliable TA injection which can be prepared in a hospital pharmacy.

METHODS

We tested the two methods previously reported for purifying commercial TA preparations, the sedimentation and the filtration and backflushing methods. We developed a new TA injection made of pure TA suspended in 0.5% sodium hyaluronate. We measured the TA content in each preparation by high-performance liquid chromatography to evaluate the three methods.

RESULTS

In the sedimentation purification method, the TA content of a nominal 4-mg preparation varied from 1.43 to 7.37 mg, and the average recovery rate was 91.6%. In the filtration and backflushing method, TA content was 0.10-10.33 mg and recovery was 59.5%. In the TA injection we developed, the mean TA content was 102.5% (SD, 0.24; CV, 2.9%). The stability of this preparation was 99% after sterilization, and 97% after 3 months of storage.

CONCLUSIONS

The results of our investigation showed that the purification methods used for commercial preparations are simple and easy but not precise enough for an intravitreal injection. In contrast, the TA injection prepared by our method is reliable, stable, and safe enough for clinical use.

Simple HPLC determination of benzalkonium chloride in ophthalmic formulations containing antazoline and tetrahydrozoline

A simple and rapid analytical procedure for routine quantification of n-C12H25 and n-C14H29 benzalkonium chloride (C-12 and C-14 BKC) homologs in ophthalmic formulations containing antazoline HCl and tetrahydrozoline HCl by high-performance liquid chromatography was developed and validated. The ophthalmic solution samples can be directly analyzed by reversed-phase on HiQ-Sil C18 column (4.6 mm x 150 mm, i.d., 5-microm particle size) with acetonitrile-sodium acetate buffer (pH 5.0; 0.2 M) (70:30, v/v) as mobile phase. UV Detection was carried out at 262 nm. The method was linear over the selected concentration and ranged from 0.03 to 0.10 mg/ml (r2 = 0.9999) and from 0.01 to 0.05 mg/ml (r2 = 0.9979) for C-12 and C-14 BKC homologs, respectively. The mean percent recoveries were 100.2 and 102.6 and the percent CV values were 1.3 and 3.5 for C-12 and C-14 BKC homologs, respectively. The results demonstrated the good linearity, accuracy, and precision. The method was applied to determine two commercial ophthalmic formulations, and the percent label amounts of total BKC contents were found to be 99.7 and 103.2.

Characterization of the novel ophthalmic drug carrier Sophisen in two of its derivatives: 3A Ofteno and Modusik-A Ofteno

Sophisen, a new ophthalmic drug carrier, was characterized using physicochemical and morphological criteria. Diclofenac belongs to a nonsteroidal anti-inflammatory molecule group and its ophthalmic use avoids side effects produced by steroid drugs. Cyclosporine-A is a cyclic peptide used as an immunosuppressive when administrated systemically. Its application in ophthalmology has been reported, but it is a very poor soluble drug. Diclofenac sodium and Cyclosporine-A were mixed with Sophisen to render two new ophthalmic solutions that were named 3A Ofteno and Modusik-A Ofteno, respectively. Based on transmission electron microscopy and dynamic light scattering studies, we concluded that Sophisen is a polydisperse solution with a molecular weight of 413 +/-122 kDa, whereas 3A Ofteno and Modusik-A Ofteno are monodisperse solutions with molecular weights of 169 +/- 44 and 153 +/- 10, respectively. Sophisen was shown to be a good carrier for diclofenac sodium as evaluated by passive diffusion through the cornea. A comparative study suggests that diclofenac applied as eye drops was better tolerated when associated with Sophisen. In addition, Modusik-A Ofteno, a new aqueous solution of Cyclosporine-A, improved tear production in patients with moderate or severe dry eye condition.

Influence of inorganic mobile phase additives on the retention, efficiency and peak symmetry of protonated basic compounds in reversed-phase liquid chromatography

Inorganic eluent additives affect the retention of protonated basic analytes in reversed-phase HPLC. This influence is attributed to the disruption of the analyte solvation-desolvation equilibria in the mobile phase, also known as "chaotropic effect". With an increase of counteranion concentration analyte retention increases with concomitant decrease in the tailing factor. Different inorganic counteranions at equimolar concentrations affect protonated basic analyte retention and peak symmetry to varying degrees. The effect of the concentrations of four different inorganic mobile phase additives (KPF6, NaClO4, NaBF4, NaH2PO4) on the analyte retention, peak symmetry, and efficiency on a C8-bonded silica column has been studied. The analytes used in this study included phenols, toluene, benzyl amines, beta-blockers and ophthalmic drugs. The following trend in increase of basic analyte retention factor and decrease of tailing factor was found: PF6- > ClO4- approximately BF4- > H2PO4-. With the increase of the counteranion concentration greater analyte loading could be achieved and consequently an increase in the apparent efficiency was observed until the maximum plate number for the column was achieved. At the highest concentration of counteranions, the peak efficiency for most of the basic compounds studied was similar to that of the neutral markers. In contrast, the neutral markers, such as phenols, showed no significant changes in retention, efficiency or loading capacity as counteranion concentration was increased.

Simple and rapid analysis of endocrine disruptors in liquid medicines and intravenous injection solutions by automated in-tube solid-phase microextraction/high performance liquid chromatography

A simple and rapid method was developed for analyzing contamination of endocrine disruptors in liquid medicines and intravenous injection solutions. Endocrine disrupting compounds such as bisphenol A (BPA), alkylphenols and phthalates were quantitated by on-line in-tube solid-phase microextraction coupled with high performance liquid chromatography (in-tube SPME/HPLC) with UV detection. The liquid medicines and intravenous injection solutions could be used directly without any pretreatment, and the BPA, alkylphenols and phthalates in these solutions were automatically analyzed. The limits of quantification for these compounds were 1-10 ng/ml. Recoveries of these compounds spiked to the intravenous injection solutions was over 80%, except for some phthalates. Di-n-butyl phthalate (DBP) was detected at a concentration of 7-60 ng/ml in most intravenous injection solutions in plastic containers, but it was not detected in solutions in glass bottles. Diethyl phthalate, di-n-propyl phthalate, DBP and di-2-ethylhexyl phthalate (DEHP) were also detected in syrup, lotion and eye drops in plastic containers. On the other hand, BPA and alkylphenols were not detected at all in these solutions. DEHP contamination from an administration set increased when total vitamin formulation was added to the infusion solution. DEHP was easily leached from polyvinyl chloride tubing by polysorbate 80. The in-tube SPME/HPLC method is simple, rapid and automatic, and it provides a useful tool for the screening and determination of endocrine disruptor contamination in liquid medicines and intravenous injection solutions.

Ion-association method for the colorimetric determination of neomycin sulphate in pure and dosage forms

A simple, fairly rapid, sensitive and accurate method is described for the colorimetric determination of neomycin sulphate (NMS), based on the measurement of the absorbance of the extracted organic soluble ion-association complex formed between neomycin dictation and a bulky counter anion. Different chromotropic acid azo dyes were examined as counter ions. The effect of pH, the counter ion concentration, sequence of addition and solvents for extraction were also illustrated. The most suitable system is based on reagent VIII (pH 7.5) with chloroform as the extraction solvent. The use of other counter ions, in conjunction with their respective solvents, was found to be less sensitive. The neomycin-reagent VIII system exhibits negligible or no interference when used for the determination of up to 58 microgml(-1) of NMS in the presence of several drug excipiences. The method has been used for the determination of up to 58 microgml(-1) with a good recovery (99.8+/-1.5%), and the precision is supported by the low relative standard deviation </=1.35%. The sensitivity is discussed and the results are compared with the official method. The proposed method was applied successfully to the determination of NMS in pure and dosage forms, with a good precision and accuracy compared to the official one.

Spectrophotometric determination of phenylephrine hydrochloride in pharmaceuticals by flow injection analysis exploiting the reaction with potassium ferricyanide and 4-aminoantipyrine

This paper presents a method for the determination of phenylephrine hydrochloride in pharmaceuticals by spectrophotometric flow injection analysis exploiting the reaction with potassium ferricyanide and 4-aminoantipyrine, which leads to the formation of a condensation product with strong absorptivity at 500 nm. The linear dynamic range was between 0.95 and 9 mg/L, with a limit of detection of 0.2 mg/L and a sampling throughput of 120 samples per hour. The method was applied to eyewashes and nasal decongestant liquid medicines.

Biopharmaceutical assessment of eye drops containing aloe (Aloe arborescens Mill.) and neomycin sulphate

The subject of the studies was eye drops made of aloe, containing the group of aloe chemical substances of anti-inflammatory use and neomycin sulphate. The aim of the studies was to evaluate the permeability of biologically active aloe substances, determined as aloenin, through synthetic lipophilic and hydrophilic membranes in a standard perfusion apparatus and in vitro verification of the transport possibilities of these substances through the isolated cornea of pig's eye. The permeability process of biologically active aloe substances determined as aloenin, through synthetic lipophilic and hydrophilic membranes, was analyzed using the first-order kinetics. Estimated quotas of permeability rate constant show that the investigated chemical compounds of aloe, included in the eye drops, diffused through the applied membranes. The studies of permeability through isolated pig's cornea proved that biologically active aloe substances could not overcome this biological barrier. On the basis of biopharmaceutical studies it can be concluded that the eye drops containing aloe and neomycin sulphate, due to the lack of permeating abilities through the eye cornea, should be particularly useful in the treatment of inflammations and infections of external parts of the eye, such as conjuctiva, eyelid edges, lacrimal sac and cornea.

Iminodibenzyl as a novel coupling agent for the spectrophotometric determination of sulfonamide derivatives

A rapid, selective and simple spectrophotometric method for the determination of sulfa-drugs is described. The method is based on the formation of violet colored azo product by the diazotization of sulfonamides, viz. sulfathiazole (SFT), sulfadiazine (SFD), sulfacetamide (SFA), sulfamethoxazole (SFMx), sulfamerazine (SFMr), sulfaguanidine (SFG) and sulfadimidine (SFDd) followed by a coupling reaction with iminodibenzyl in alcohol medium. Absorbance of the resulting violet azo product is measured at 570-580 nm and is stable for 24 h at 27 degrees C. Beer's law is obeyed in the concentration range of 0.05-6.0 microg ml(-1) at the wavelength of maximum absorption. The method is successfully employed for the determination of sulfonamides in various pharmaceutical preparations and common excipients used as additives in pharmaceuticals do not interfere in the proposed method. The method offers the advantages of simplicity, rapidity and sensitivity without the need for extraction or heating. A reaction mechanism is proposed for the formation of the violet azo product.

Microbial contamination of eye drops

The microbial contamination of eye drops at the Eye Clinic was studied. In total, 92 eye drop bottles were examined. 43 bottles were opened and used and 49 were unopened and sealed. The contamination rate was found to be 10.2% in unopened bottles and 34.8% in opened bottles. The opened bottles had been used for two weeks. Six of the samples yielded coagulase-negative Staphylococci and nine samples yielded one or two different microorganisms. The contamination rate in bottles containing the preservative benzalkonium chloride was 34.4%. Among unopened eye drop bottles two samples yielded S. aureus, two coagulase-negative Staphylococci and one Bacillus spp.

Qualitative and quantitative determination of poloxamer surfactants by mass spectrometry

Poloxamers are polyethylene-polypropylene glycol linear co-polymers. A simple matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) method has been developed for the determination of the average molecular weight of poloxamers. The molecular mass of five standard poloxamers determined by MALDI closely corresponds to that specified by the manufacturers, and no mass distribution effects were observed. Quantitation of distributions based on the molecular mass envelope using electrospray (ES) ionization was unsuccessful. To overcome this problem, quantitation was based on fragment ions (m/z 45 and 59) which gave reproducible signals using a very high orifice voltage ( approximately 200 eV). Poloxamer concentrations were determined accurately with a good linear response using the standard addition method. We believe that the use of very small fragment ions for quantitation of polymers may become a widely applicable general technique.

[Determination of alpha-naphthylacetic acid by high performance liquid chromatography]

A high performance liquid chromatographic method for the determination of alpha-naphthylacetic acid has been established on a Hypersil C18 column(4.6 mm i.d. x 250 mm, 5 microns), with the mobile phase of methanol-water-phosphoric acid(60:40:0.35, V/V), and UV detection at 272 nm. The linear correlation was observed within the range of 16 mg/L-1,000 mg/L(r = 0.9997). The RSD was 0.8%(n = 5). The method is simple and accurate.

Anti-inflammatory, antioxidant and antimicrobial activity of Ophthacare brand, an herbal eye drops

In the present study, the herbal preparation of Ophthacare brand eye drops was investigated for its anti-inflammatory, antioxidant and antimicrobial activity, using in vivo and in vitro experimental models. Ophthacare brand eye drops exhibited significant anti-inflammatory activity in turpentine liniment-induced ocular inflammation in rabbits. The preparation dose-dependently inhibited ferric chloride-induced lipid peroxidation in vitro and also showed significant antibacterial activity against Escherichia coli and Staphylococcus aureus and antifungal activity against Candida albicans. All these findings suggest that Ophthacare brand eye drops can be used in the treatment of various ophthalmic disorders.

Polarographic determination of zinc in eye drops and validation of the method

Differential pulse polarography was used to study the electrode behavior of zinc (II) in various stock solutions. In view of the surfactants like methylcellulose derivatives present in the pharmaceutical preparations examined, which affected the course of the polarograms recorded, 0.5 mol l-1 ammonium buffer, pH 10.0, was found to be an optimum solution for the study. In a strong alkaline solution, zine currents were no longer suppressed by the methylcellulose derivatives. To compare the polarographic data obtained for "Cincol", "Oculosan" and "Visine Sensitive" eye drops, zinc (II) was determined in those eye drops by atomic absorption spectrometry without mineralization. Statistical evaluation of the data showed the DPP procedure developed to be characterized by satisfactory accuracy and precision (RSD : 0.93% ("Cincol"), 0.82% ("Oculosan"), 0.82%; ("Visine Sensitive")).

Evaluation of microdialysis sampling of aqueous humor for in vivo models of ocular absorption and disposition

The dynamics of beta-adrenergic-associated reductions in aqueous humor production for treatment of elevated intraocular pressure are not well understood. In particular, the relationship between ocular pharmacokinetics and pharmacodynamics has yet to be established. This study was undertaken to develop a procedure for examining the ocular absorption and disposition of topically administered ophthalmic beta-adrenergic antagonists in individual animals. Dogs were anesthetized with isoflurane and a microdialysis probe was implanted in the anterior chamber of one eye and perfused with 0.9% saline at a rate of 2 microliters min-1. 3H-propranolol was administered by intracameral injection or topically. Each dog received intracameral and topical propranolol, in alternate eyes on separate days, in a randomized cross-over fashion. Microdialysis probe effluent was collected every 5 min for > or = 2.5 h; concentrations of propranolol were determined by liquid scintillation spectroscopy and were corrected for probe recovery of the substrate as determined by in vivo retrodialysis (approximately 46%) to estimate aqueous humor concentrations. In separate experiments in rabbits, microdialysis probes were implanted in each eye. 3H-propranolol was administered topically to one eye; the contralateral eye received intracameral 3H-propranolol. Model-independent pharmacokinetic parameters for each treatment phase were calculated. The mean +/- S.D. times to peak concentration of propranolol in aqueous humor were 86.6 +/- 47.6 min in the dog and 54.1 +/- 20.4 min in the rabbit. The terminal rate constant was 0.0189 +/- 0.00429 min-1 in the dog vs. 0.00983 +/- 0.00546 min-1 in the rabbit. Intraocular tissue availability of propranolol differed markedly between the dog (n = 3) and rabbit (n = 3) (approximately 0.056 in the dog vs. approximately 0.55 in the rabbit). These results demonstrate the utility of microdialysis sampling for examination of ocular pharmacokinetics.

Stability of cefazolin sodium eye drops

OBJECTIVE

Assessing the stability of cefazolin sodium in preservative-free and preservative-containing eye drops.

METHOD

Extemporaneous formulations of eye drops were prepared from a commercially-available parenteral product of cefazolin sodium: eye drops 'A' contained 50mg/ml of cefazolin sodium in 0.45% w/v sodium chloride solution, and eye drops 'B' contained 50 mg/ml, 0.005% w/v thiomersal and 1% w/v glycerol in water-for-injection. Cefazolin sodium concentrations in these eye drops were monitored by a stability-indicating HPLC assay method. Measurements of pH and osmolality, as well as tests for microbial contamination, were conducted.

RESULTS

The eye drops stored at 4 degrees C were stable for 42 days with minimal changes in pH and osmolality, but eye drops stored at room temperature were only stable for a few days with greater increments in pH and osmolality. None of the samples cultured had bacterial or fungal growth after 7 days of incubation.

CONCLUSION

Extemporaneously prepared formulations of cefazolin are unstable at room temperature and should be stored in a refrigerator.

Determining fluid level in a translucent eye-drop bottle: transillumination by penlight

We describe an easy way to determine eye-drop contents in translucent bottles. Transillumination of eye-drop bottles from behind or the bottom by using a penlight clearly defines the fluid levels. The described procedure may prevent disposal of eye-drop bottles containing useful amounts of medication and prevent Ophthalmologists and Patients unexpectedly coming across an empty bottle.

[Incidence of hypersensitivity to antibiotics and preservatives in eye drops]

PURPOSE

To elaborate a set of contact allergens present in eye drops which could precipitate allergic conjunctivitis. Such set has not been yet described in literature.

METHODS

Basing on the most frequently used preparations, a set of 15 different substances: drugs and preservatives, was prepared to test the patients.

RESULTS

Among the 97 persons who underwent the testing, positive results were observed in 35.5%. The hypersensitivity was found for 11 of the allergens, the most often for neomycin, gentamycin, merthiolate, benzalkonium chloride, and then consecutively for kanamycin, sulfathiazole, oxytetracycline, chloramphenicol, penicillin, boric acid and parabens.

Applications of capillary electrophoresis in the eye-care pharmaceutical industry

The speed and resolution of capillary electrophoresis (CE), combined with its low cost and low volume requirements, make it a promising method of separating eye-care pharmaceuticals and analyzing the ionic composition of tears. Capillary zone electrophoresis (CZE) offers linearity, precision, and recovery comparable to high-performance liquid chromatography (HPLC) at a fraction of its cost. In addition, CZE separates and quantitates cocoamphocarboxyglycinate in the presence of a non-ionic fatty acid amide surfactant seven times faster than HPLC. CE easily detects such cations as sodium and potassium in human tears.

Analytical chiral separation of the stereoisomers of a novel carbonic anhydrase inhibitor and its deethylated metabolite, and the assignment of absolute configuration of the human metabolite and chiral degradation products

Several approaches to the separation of four stereoisomers, 1-4, of a novel, topically active, carbonic anhydrase inhibitor, 1, with two chiral centers in the molecule and four isomers, 5-8, of its chiral metabolite, 5, were evaluated. These methods include nonchiral derivatization followed by separation on chiral stationary phases (CSPs) and chiral derivatization and separation on nonchiral columns and on CSPs. Baseline separation of stereoisomers 1-4 was achieved in less than 15 min after chiral derivatization with (S)-(+)-1-(1-naphthyl)ethyl isocyanate (NEIC) and chiral chromatography on a (R)-N-(3,5-dinitrobenzoyl)phenyl glycine (DNBPG) column under normal phase (NP) conditions. Similarly, isomers 5-8 were baseline separated in less than 20 min after derivatization with NEIC and chromatography on nonchiral (nitrophenyl) and chiral [(S)-(3,5-dinitrobenzoyl)leucine; DNBL] columns in series under the same NP chromatographic conditions. Only partial separation of the diastereomeric derivatives was observed on a variety of nonchiral columns. In addition, all other direct and indirect chiral separation approaches gave only partial separation of at least two stereoisomers within the group of 1-4 or 5-8. The details of chiral separations using various methods and separation (alpha) and capacity factors (k') of the derivatized isomers 1-8 on a series of chiral and nonchiral columns are presented. Using these methods, the absolute configuration of the human metabolite of 1 was established as S1S2 (5), and the heat (HD) and light (LD) degradation products of 1 as R1S2 (3) and S1S2 (5), respectively.