Enhancement of pharmacokinetic and pharmacological behavior of ocular dorzolamide after factorial optimization of self-assembled nanostructures

Breaking Barriers in Eye Treatment: Polymeric Nano-Based Drug-Delivery System for Anterior Segment Diseases and Glaucoma

The eye has anatomical structures that function as robust static and dynamic barriers, limiting the penetration, residence time, and bioavailability of medications administered topically. The development of polymeric nano-based drug-delivery systems (DDS) could be the solution to these challenges: it can pass through ocular barriers, offering higher bioavailability of administered drugs to targeted tissues that are otherwise inaccessible; it can stay in ocular tissues for longer periods of time, requiring fewer drug administrations; and it can be made up of polymers that are biodegradable and nano-sized, minimizing the undesirable effects of the administered molecules. Therefore, therapeutic innovations in polymeric nano-based DDS have been widely explored for ophthalmic drug-delivery applications. In this review, we will give a comprehensive overview of polymeric nano-based drug-delivery systems (DDS) used in the treatment of ocular diseases. We will then examine the current therapeutic challenges of various ocular diseases and analyze how different types of biopolymers can potentially enhance our therapeutic options. A literature review of the preclinical and clinical studies published between 2017 and 2022 was conducted. Thanks to the advances in polymer science, the ocular DDS has rapidly evolved, showing great promise to help clinicians better manage patients.

Drug-Loaded Polymeric Micelles Based on Smart Biocompatible Graft Copolymers with Potential Applications for the Treatment of Glaucoma

Glaucoma is the second leading cause of blindness in the world. Despite the fact that many treatments are currently available for eye diseases, the key issue that arises is the administration of drugs for long periods of time and the increased risk of inflammation, but also the high cost of eye surgery. Consequently, numerous daily administrations are required, which reduce patient compliance, and even in these conditions, the treatment of eye disease is too ineffective. Micellar polymers are core–shell nanoparticles formed by the self-assembly of block or graft copolymers in selective solvents. In the present study, polymeric micelles (PMs) were obtained by dialysis from smart biocompatible poly(ε-caprolactone)-poly(N-vinylcaprolactam-co-N-vinylpyrrolidone) [PCL-g-P(NVCL-co-NVP)] graft copolymers. Two copolymers with different molar masses were studied, and a good correlation was noted between the micellar sizes and the total degree of polymerisation (DPn) of the copolymers. The micelles formed by Cop A [PCL120-g-P(NVCL507-co-NVP128)], with the lowest total DPn, have a Z-average value of 39 nm, whereas the micellar sizes for Cop B [PCL120-g-P(NVCL1253-co-NVP139)] are around 47 nm. These PMs were further used for the encapsulation of two drugs with applications for the treatment of eye diseases. After the encapsulation of Dorzolamide, a slight increase in micellar sizes was noted, whereas the encapsulation of Indomethacin led to a decrease in these sizes. Using dynamic light scattering, it was proved that both free and drug-loaded PMs are stable for 30 days of storage at 4 °C. Moreover, in vitro biological tests demonstrated that the obtained PMs are both haemo- and cytocompatible and thus can be used for further in vivo tests. The designed micellar system proved its ability to release the encapsulated drugs in vitro, and the results obtained were validated by in vivo tests carried out on experimental animals, which proved its high effectiveness in reducing intraocular pressure.

Simultaneous determination of dorzolamide and timolol by first-order derivative UV spectroscopy in simulated biological fluid for in vitro drug release testing

Dorzolamide hydrochloride and timolol maleate is a well-established fixed-dose combination for the treatment of glaucoma worldwide. The utilization of simulated biological fluids can give a superior understanding of the release mechanisms and practicable in vivo nature of a dosage form that can improve the predictive potential of in vitro drug release testing. No method has been reported so far for the simultaneous estimation of dorzolamide and timolol in simulated tear fluid. In the present study, a simple, precise, and accurate first-order derivative ultraviolet spectrophotometric method for the routine analysis of dorzolamide and timolol in simulated tear fluid is proposed for in vitro drug release testing. The developed method was validated as per International Conference on Harmonization guidelines Q2 (R1). First-order derivative UV spectrophotometry was successfully applied to separate the overlapping peaks of dorzolamide and timolol by measuring peak amplitude at 251.80 nm and absorbance at 295.00 nm, respectively. The method was found to be accurate and precise, with a recovery range of 98.0 -101.0% and low relative standard deviations (<2.0%). The developed method was successfully applied for in vitro drug release testing of in-house in situ gel and marketed eye drops containing dorzolamide and timolol. Various mathematical models were adopted to fit the in vitro drug release profile. It was observed that the drug release of both drugs from the in situ gel and the marketed solution were best fitted by the Higuchi and first-order kinetic models, respectively. Moreover, the analysis of variance (ANOVA) provision was used for the validation of results. Overall, with the advantages of simple and fast operations, as well as reliability, the proposed method offers an ideal platform for routine analysis as compared to other high-cost and time-consuming chromatographic techniques. Having access to such a robust method will encourage the use of simulated tear fluid for in vitro drug release testing of ocular products and help to predict the in vivo performances of ophthalmic preparations.

Chromatographic bioanalysis of antiglaucoma drugs in ocular tissues

Glaucoma is a heterogeneous group of multifactorial optic neuropathies and the leading cause of irreversible blindness and visual impairment. Epidemiological data has estimated that in 2020 there will be more than 80 million individuals affected by the disease worldwide. Nowadays, intraocular pressure (IOP) lowering is carried out mainly by pharmacotherapy, with different drugs. The study of ocular pharmacokinetics of antiglaucoma drugs, crucial for better understanding of ocular distribution, bioavailability, and pharmacodynamic parameters, can benefit the development of antiglaucoma drugs or formulations. Bioanalysis of drugs in ocular matrices is still underestimated, since it is challenging and rarely performed. Therefore, this review summarized the chromatographic methods employed for the quantification of several antiglaucoma drugs in different ocular matrices, discussing bioanalytical steps, such as sample preparation, separation, and detection. Animals and matrices as well as the challenges faced in ocular bioanalysis were also discussed. Ocular bioanalysis has been performed mainly in rabbits, the most adequate animal model for ocular studies. The matrix most used is aqueous humor, because it is cleaner and easier to sample. Sample preparation was carried out primarily employing classic techniques, such as liquid-liquid extraction, protein precipitation, and solid-phase extraction, with conventional solvents and sorbents. Chromatographic separation was achieved predominantly by reversed-phase liquid chromatography. Ultraviolet spectrophotometry and tandem mass spectrometry prevailed for detection, although other techniques, such as fluorimetry, have also been used. It was evidenced that more efforts must be directed towards miniaturized, eco-friendly, and non-terminal sampling for sample preparation. In its turn, ultra high-performance liquid chromatography and mass spectrometry should gain prominence in ocular bioanalysis for separation and detection, respectively, since it combines high separation capacity with selectivity and sensitivity, in addition to being an environmental friendly approach.

Cubogel as potential platform for glaucoma management

The aim of this work is to survey the potential of cubogel as an ocular dosage form to boost the corneal permeability of Dorzolamide Hydrochloride DZ; an antiglaucomal drug. DZ-loaded cubosomal dispersions were prepared according to Box-Behnken design, where the effect of independent variables; Monoolein MO concentration (2.5, 5 and 7.5%w/w), Pluronic^® F127 concentration (0.25, 0.5 and 0.75%w/w) and magnetic stirrer speed of (400, 800 and 1200 rpm) was studied on PS (nm), Zp (−mV) and Q 2 h (%) respectively. The prepared formulae were characterized via drug content DC (%), particle size PS (nm), polydispersity index PDI, zeta potential Zp (−mV), in-vitro drug release (Q 2 h%) and finally TEM. The optimized formulation composed of: 6.13% w/w of MO, 0.75% w/w of F127 and prepared at 1200 rpm stirring speed was chosen based on the criteria of minimum PS (nm), maximum Zp (−mV) and minimum Q 2 h (%). Results revealed that the optimum formula showed PS of 153.3 ± 8.4 n, Zp of 32 ± 3 −mV and 37.78 ± 1.3% released after 2 h. Carbopol 934 (1% w/v) as gelling agent was used to prepare the optimum cubogel, which was further evaluated by DSC, ex-vivo permeation and stability studies at 4 °C for three months. Moreover, in vivo studies of the optimized cubogel include; draize test, histological examination, confocal laser scanning microscopy (CLSM) and intraocular pressure (IOP) measurement. Results revealed that the optimized cubogel was considerably safe, stable and competent to corneal delivery as assured by draize and histological examination. CLSM showed a deeper penetration of more than 2.5-fold. A higher bioavailability (288.24 mg. h/ml) was attained from cubogel compared to the market product Trusopt^® eye drops (115.40 mg. h/ml) following IOP measurement. Therefore, DZ-loaded cubogel could be considered as promising delivery system to boost the transcorneal permeation hence corneal bioavailability of DZ as antiglaucomal drug.

Analysis of pharmaceuticals and small molecules in aqueous humor

Aqueous humor (AH) is a transparent fluid found in the anterior chamber of the eye. The circulating AH nourishes the cornea and lens and removes the metabolic waste moving through the ocular chambers and drains from the eye to the venous blood. Analysis of drugs in AH is necessary to evaluate their pharmacokinetics parameters, which may be crucial to avoid potential adverse effects. Analysis of endogenous components of AH may help to understand its physiology as well as changes evoked by pathological situation. This review describes analytical methods used for determination of pharmaceuticals and small endogenous molecules in AH, focusing on sample preparation procedures and analytical techniques. Studies on human and animal samples are included. After inspection and filtering of records found in PubMed about 100 research papers were selected to review. In these articles AH samples of human and rabbit origin were studied most often. Sample evaporation and reconstitution in smaller solvent volume was the most popular method for analyte pre-concentration. Acetonitrile, methanol or mixture of both solvents were used most often for protein precipitation.