Stability of extemporaneously prepared ophthalmic solutions for mydriasis.

PURPOSE: Results of an evaluation of the physical and chemical stability of extemporaneously prepared adult and pediatric ophthalmic solutions containing combinations of phenylephrine, tropicamide, and cyclopentolate are reported. METHODS: A stability study was conducted to help determine the feasibility of innovative formulations to meet an unmet clinical need for combination mydriatic ophthalmic eyedrops. An adult mydriatic ophthalmic solution containing phenylephrine hydrochloride 2.5% and tropicamide 1.0% and a pediatric formulation containing phenylephrine hydrochloride 2.5%, tropicamide 0.5%, and cyclopentolate hydrochloride 0.5% were prepared using proper aseptic techniques. Triplicate samples of each formulation were stored for 60 days at refrigeration temperatures (2-8 °C) and analyzed on day 0 and days 7, 14, 28, and 60. At each time point, the stability samples were assessed by visual inspection, pH measurement, and stability-indicating high-performance liquid chromatography (HPLC) analysis. RESULTS: Over the 60-day storage period, there was no significant change in the visual appearance or pH level of any of the adult or pediatric solution samples. The results of HPLC analysis indicated that all samples retained 97-102% of the initial drug concentrations for up to 60 days. CONCLUSION: Both adult and pediatric ophthalmic formulations containing combinations of phenylephrine, tropicamide, and cyclopentolate were stable physically and chemically for up to 60 days when stored at refrigeration temperatures (2-8 °C).

Cubic liquid crystalline nanoparticles: optimization and evaluation for ocular delivery of tropicamide.

The purpose of this study was to investigate the potential of cubic liquid crystalline nanoparticles for ocular delivery of tropicamide. Ultrasound-assisted fragmentation of cubic liquid crystalline bulk phases resulted in cubic liquid crystalline nanoparticles employing Pluronic F127 as dispersant. The effects of process variables such as sonication time, sonication amplitude, sonication depth, and pre-mixing time on particle size and polydispersity index was investigated using central composite design. The morphology of tropicamide-loaded nanoparticles was found to be nearly cubical in shape by transmission electron microscopy observation. Further, small angle X-ray scattering experiment confirmed the presence of D and P phase cubic structures in coexistence. The optimized tropicamide-loaded cubic nanoparticles showed in vitro corneal permeation of tropicamide across isolated porcine cornea comparable to its commercial preparation, Tropicacyl®. Ocular tolerance was evaluated by Hen's egg-chorioallantoic membrane test and histological studies. The results of in vivo mydriatic response study demonstrated a remarkably higher area under mydriatic response curve (AUC0→1440 min) values of cubic nanoparticles over Tropicacyl® indicating better therapeutic value of cubic nanoparticles. Furthermore, tropicamide-loaded cubic nanoparticles exhibited prolonged mydriatic effect on rabbits as compared to commercial conventional aqueous ophthalmic solution.

The investigation of the interaction between Tropicamide and bovine serum albumin by spectroscopic methods.

The fluorescence and ultraviolet-visible (UV-Vis) spectroscopy were explored to study the interaction between Tropicamide (TA) and bovine serum albumin (BSA) at three different temperatures (292, 301 and 310K) under imitated physiological conditions. The experimental results showed that the fluorescence quenching mechanism between TA and BSA was static quenching procedure. The binding constant (Ka), binding sites (n) were obtained. The corresponding thermodynamic parameters (ΔH, ΔS and ΔG) of the interaction system were calculated at different temperatures. The results revealed that the binding process is spontaneous, hydrogen binds and vander Waals were the main force to stabilize the complex. According to Förster non-radiation energy transfer theory, the binding distance between TA and BSA was calculated to be 4.90 nm. Synchronous fluorescence spectroscopy indicated the conformation of BSA changed in the presence of TA. Furthermore, the effect of some common metal ions (Mg(2+), Ca(2+), Cu(2+), and Ni(2+)) on the binding constants between TA and BSA were examined.

Evaluation of tropicamide-loaded tamarind seed xyloglucan nanoaggregates for ophthalmic delivery.

The present study was aimed to prepare tamarind seed nanoaggregates and its evaluation for ophthalmic delivery. The preparation of tropicamide-loaded tamarind seed xyloglucan nanoaggregates was optimized using face centred central composite experimental design, employing the concentrations of tamarind seed xyloglucan and Poloxamer-407, as independent variables. The results revealed that concentration of TSX has a significant antagonistic effect on particle size, while poloxamer displayed a significant synergistic effect on encapsulation efficiency. The optimal concentrations of TSX and poloxamer were found to be 0.45% (w/v) and 0.5% (w/v) respectively. The optimized formulation of tropicamide-loaded TSX nanoaggregates showed a significantly higher corneal permeation of tropicamide across the isolated goat cornea compared to commercial conventional aqueous formulation. The results revealed excellent mucoadhesive properties of TSX nanoaggregates. Further, the tropicamide-loaded TSX nanoaggregates formulation showed excellent ocular tolerance and biocompatibility as determined by hen's egg test chorioallantoic membrane and resazurin assay on Vero cell lines.

Carboxymethyl tamarind kernel polysaccharide nanoparticles for ophthalmic drug delivery.

Tropicamide-loaded carboxymethyl tamarind kernel polysaccharide (CMTKP) nanoparticles were prepared and evaluated for ocular delivery. Preparation of ionotropically gelled CMTKP nanoparticles was optimized employing three-levels, two-factor central composite design. Concentration of polymer and crosslinker had significant synergistic effect on particle size and % encapsulation efficiency. The optimal calculated parameters were concentrations of CMTKP 0.10% (w/v) and calcium chloride 0.11% (w/v). The optimized tropicamide-loaded CMTKP formulation showed ex vivo corneal permeation of tropicamide across isolated goat cornea comparable to its aqueous solution. Further, the mucoadhesive and non-irritant nature of CMTKP nanoparticles indicate their suitability as ocular delivery system.

Determination of tropicamide and its major impurity in raw material by the HPLC-DAD analysis and identification of this impurity using the off-line HPLC-FT-IR coupling.

This study presents TLC, HPLC-DAD and HPLC-FT-IR analyses concerning the detection, identification and determination of organic impurities of commercial tropicamide ((R,S)-N-ethyl-3-hydroxy-2-phenyl-N-(4-pyridylmethyl)propanamide) as a medical substance designed for the production of eye drops. In the examined samples from several random production batches, only one impurity (defined by Ph. Eur. 6th Ed.) was discovered in the amount sufficient for the quantitative analysis. On the basis of comparison of retention times, UV and IR spectra of the impurity and its synthesized standard, this impurity was identified as apotropicamide (N-ethyl-2-phenyl-N-(4-pyridylmethyl)prop-2-enamide). For the chemical identification of organic compounds occurring in the tropicamide samples, an off-line coupling of HPLC with FT-IR was used. The structure of a standard of apotropicamide was confirmed by (1)H NMR and (13)C NMR analysis. Validation of the HPLC-DAD method of determination both tropicamide and apotropicamide in the tropicamide medical substance was performed. This method is suitable for use in the quality control of tropicamide during its production.

Effect of large volume injection of hydrophobic solvents on the retention of less hydrophobic pharmaceutical solutes in RP-LC.

Injection of large volumes of samples in solvents other than mobile phase composition has been proved for some less hydrophobic compounds. Thus, the retention behavior of several compounds of pharmaceutical interest (isosorbide-2-nitrate, isosorbide-5-nitrate, tropicamide, pentoxifylline, and methyl p-hydroxybenzoate) was studied by using different hydrophobic solvents (n-hexane, n-heptane, or i-octane) as sample solvents. Two types of stationary phases were used: octyl and octadecyl modified silica (both of Zorbax Eclipse type). The experiments showed a linear dependence between capacity factor of each solute and sample injection volume, up to maximum volume values of about 680 microL for C8 stationary phase and 580 microL for C18 stationary phase, when the solutes are no longer retained in stationary phase. Injection of large volumes of these hydrophobic solvents is thus possible in RP-LC with a gradual reduction of retention and peak efficiency. Two major conditions are however necessary in order to apply such an injection approach: the solutes must have a proper solubility in hydrophobic solvents and meanwhile they have to be less hydrophobic than the sample solvent in order to avoid competition with solvent molecules in partitioning between mobile and stationary phases.

Poly(amidoamine) dendrimers as ophthalmic vehicles for ocular delivery of pilocarpine nitrate and tropicamide.

The purpose of this study was to determine the influence of a controlled incremental increase in size, molecular weight and number of amine, carboxylate and hydroxyl surface groups in several series of poly(amidoamine) (PAMAM) dendrimers for controlled ocular drug delivery. The duration of residence time was evaluated after solubilization of several series of PAMAM dendrimers (generations 1.5 and 2-3.5 and 4) in buffered phosphate solutions containing 2 per thousand (w/v) of fluorescein. The New Zealand albino rabbit was used as an in vivo model for qualitative and quantitative assessment of ocular tolerance and retention time after a single application of 25 microl of dendrimer solution to the eye. The same model was also used to determine the prolonged miotic or mydriatic activities of dendrimer solutions, some containing pilocarpine nitrate and some tropicamide, respectively. Residence time was longer for the solutions containing dendrimers with carboxylic and hydroxyl surface groups. No prolongation of remanence time was observed when dendrimer concentration (0.25-2%) increased. The remanence time of PAMAM dendrimer solutions on the cornea showed size and molecular weight dependency. This study allowed novel macromolecular carriers to be designed with prolonged drug residence time for the ophthalmic route.

Ophthalmic vehicles containing polymer-solubilized tropicamide: "in vitro/in vivo" evaluation.

Commercial 1.0% aqueous tropicamide (TR) eyedrops are buffered to pH 4.4-5.0 to produce sufficiently stable solutions of the weakly basic, poorly soluble drug. These acidic solutions, however, are irritants and may induce copious lachrimation, thus reducing the drug bioavailability. The aim of the present study was to evaluate some solubilizing agents for the preparation of 1.0% TR ophthalmic solutions adjusted at physiologically compatible pH, potentially showing increased eye tolerance, activity, and stability when compared with standard commercial eyedrops. The tested solubilizers were two non-ionic surfactants-Tyloxapol (TY) and Cremophor EL (CR) and one polymer, Pluronic P85 (PL). Four stable 1% TR formulations, containing 3% TY, 7.5% CR, 15% PL, or 5% CR + 10% PL were submitted to mydriatic activity tests in rabbits. They improved to a small but statistically significant extent the AUC for mydriatic effect of TR in the test animals when compared with commercial 1.0% TR eyedrops.

Locomotor stimulant effects of novel phenyltropanes in the mouse.

With the hypothesis that 3-phenyltropane analogs of cocaine might be useful as cocaine medications, 17 analogs (RTI-51, RTI-55, RTI-108, RTI-112, RTI-113, RTI-116, RTI-120, RTI-121, RTI-126, RTI-139, RTI-141, RTI-150, RTI-171, RTI-177, RTI-199, RTI-204, and RTI-219) were characterized for their potency and selectivity at the monoamine transporters in a previous study. Based on their affinities to the transporters in this earlier study, the analogs were classified as nonselective (cocaine, RTI-51, RTI-55, RTI-108, RTI-112, RTI-116, RTI-126, and RTI-139) or dopamine transporter (DAT) selective (RTI-113, RTI-120, RTI-121, RTI-141, RTI-150, RTI-171, RTI-177, RTI-199, RTI-204, and RTI-219). In the present study, the locomotor stimulating effects of these analogs were compared to those of cocaine to obtain a measure of in vivo activity. Each analog was more potent than cocaine in the in vivo assay, as observed in the earlier in vitro studies. Most of these compounds were as efficacious as cocaine, but RTI-51, RTI-108, RTI-113, RTI-121, RTI-139, RTI-141, RTI-177, RTI-204, and RTI-219 were longer acting. Although no correlation between chemical structure and transporter selectivity was found, the short-acting DAT-selective analogs, RTI-120, RTI-150, RTI-171, and RTI-199, all contained a methyl group in the X position of the WIN 35,065-2 molecule. The positive correlation of the IC(50)s for the DAT to potencies for increasing locomotor activity suggested that binding to DAT was responsible for some, if not most, of the locomotor effects of these compounds. Several compounds, including RTI-113 and RTI-177, exhibited properties ideal for medications for cocaine abusers, such as an equivalent efficacy, a higher potency, and a longer duration of action as compared to cocaine.

Solubilization of tropicamide by hydroxypropyl-beta-cyclodextrin and water-soluble polymers: in vitro/in vivo studies.

1% (w/v) aqueous solutions of tropicamide (TR), a poorly water-soluble mydriatic-cycloplegic drug, are usually obtained by adjusting the pH to approximately 5.0, at the expense, however, of ocular tolerance and bioavailability. The capacity of hydroxypropyl-beta-cyclodextrin (HP-beta-CD) to solubilize TR in pH 7.4 0.02 M phosphate buffer was investigated in the absence and presence of hydrophilic polymers (PVP, CMC and HPMC). Approximately 3.5% (w/v) HP-beta-CD was required to solubilize 1% (w/v) TR in pH 7.4 buffer at room temperature. The required amount was reduced to 0.9% (w/v) by heating at 120 degrees C in the presence of 0.1% (w/v) HPMC. Mydriatic activity tests in rabbits showed an improved bioavailability and maximal mydriatic response for two CD formulations, with and without HPMC, when compared to standard 1% (w/v) TR eyedrops, buffered at pH 5.0. The improved in vivo behaviour of the CD formulations are likely due to their physiological pH, resulting in a reduced irritant effect, although an effect of HP-beta-CD on corneal permeability cannot be dismissed a priori.

Preparation and evaluation of liposomal formulations of tropicamide for ocular delivery.

Tropicamide, a mydriatic, cycloplegic drug was entrapped in liposomes. Liposomes were investigated by laser counting studies, transmission electron microscopy and differential scanning calorimetry for characterization. The precorneal clearance of liposomes was compared with solution by gamma-scintigraphy in the rabbit. The neutral liposomes failed to demonstrate significant enhancement in precorneal retention in comparison with aqueous solution. The potential of liposomes as an ophthalmic drug delivery system was investigated by comparing pupil dilatory effect of tropicamide by topical instillation, in the rabbit eye, of the solution and various drug-loaded liposomal forms, i.e. neutral liposomes, positively charged liposomes and neutral liposomes dispersed in 0.25% (w/v) polycarbophil gel. The positively charged liposomal formulation and liposomes dispersed in polycarbophil gel were found to be more effective than neutral liposomal dispersion when data were statistically treated at the 5% level of significance.