The Transcorneal Penetration of Commercial Ophthalmic Formulations Containing Timolol Maleate in Rabbit Eyes

Comparison of In Vitro Corneal Permeation and In Vivo Ocular Bioavailability in Rabbits of Three Marketed Latanoprost Formulations

BACKGROUND AND OBJECTIVE

All latanoprost formulations currently available for the treatment of glaucoma or ocular hypertension contain the same concentration of latanoprost (0.005%) but differ in excipients, which may affect corneal drug permeability or stability. This study aimed at comparing corneal penetration of three marketed latanoprost solutions with different excipient formulations in in vitro and in vivo drug permeability studies.

METHODS

Three latanoprost formulations were tested under good laboratory practice conditions: a formulation containing benzalkonium chloride (BAK) but no surfactant (Preserved latanoprost); the same formulation except preservative-free (PF) without BAK or surfactant (SF) (PF SF latanoprost); and a different formulation without BAK but containing a non-ionic surfactant (MGHS 40 at 5%) combined with thickening agents (Carbomer 974P, Macrogol 4000) (PF latanoprost). Corneal permeation of latanoprost acid (LAT) was first determined in vitro using a reconstructed human corneal epithelium tissue. Then, in vivo pharmacokinetic studies were performed on pigmented rabbits, for which LAT concentration was measured in the aqueous humour (AH) and iris-ciliary body (ICB).

RESULTS

In vitro, the cumulative transport of LAT was linear between 1 h and 4 h for preserved latanoprost and PF SF latanoprost, and LAT concentrations matched exactly at each timepoint. By contrast, the permeation of PF latanoprost was linear between 2 h and 12 h and was significantly lower than that of preserved latanoprost and PF SF latanoprost at 4 and 8 h (p < 0.001). In rabbits, the concentrations of LAT in AH and ICB were not statistically different between preserved latanoprost and PF SF latanoprost at each timepoint, except at 1 h in ICB (p = 0.005). By comparison, the LAT concentration of PF latanoprost was statistically (p < 0.05) lower than that of preserved latanoprost and PF SF latanoprost in AH and ICB from 0.5 to 3 h.

CONCLUSION

BAK did not influence the corneal penetration of latanoprost in in vitro and in vivo studies. The formulation containing a non-ionic surfactant resulted in lower and slower ocular penetration compared with preserved or PF SF formulations. This raises questions about the relevance of BAK and some surfactants in enhancing corneal penetration of ocular formulations.

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.

Ocular and systemic pharmacokinetics of brimonidine and brinzolamide after topical administration in rabbits: comparison between fixed-combination and single-drug formulations

AIM

The aim of this study was to compare the ocular and systemic absorption of brimonidine (BMD) and brinzolamide (BZM) in rabbits after the topical administration of a fixed-combination ophthalmic suspension of 0.1% BMD tartrate and 1% BZM (FCBB) with that after the administration of the respective single-drug formulations.

MATERIALS AND METHODS

Ocular and systemic drug absorption was estimated by determining BMD and BZM concentrations in the aqueous humor, retina/choroid, vitreous body, and blood/plasma by liquid chromatography/tandem mass spectrometry after the administration of FCBB, 0.1% BMD tartrate ophthalmic solution (0.1% BMD), or 1% BZM ophthalmic suspension (1% BZM) to rabbits.

RESULTS

In concomitant administration, instilling 0.1% BMD and 1% BZM successively without interval lowered aqueous humor concentrations of both drugs compared to those observed with a 5-min interval. After FCBB administration, BMD and BZM concentrations in the aqueous humor were comparable with those observed after the administration of 0.1% BMD and 1% BZM, whereas BMD concentrations in posterior ocular tissues were equal to or higher than those observed after 0.1% BMD. Plasma BMD concentrations following the administration of FCBB were 0.8-fold lower than those after 0.1% BMD; no remarkable differences were observed in blood BZM concentrations for both formulations.

CONCLUSIONS

FCBB achieved drug distribution in the aqueous humor and systemic exposure that were comparable to those for the single-drug formulations. The viscosity of FCBB may increase BMD distribution in the retina/choroid. The administration interval affects ocular drug absorption with the concomitant administration of 0.1% BMD and 1% BZM, which can be overcome by using the fixed-combination of both drugs.

Nanotechnology for Medical and Surgical Glaucoma Therapy-A Review

Glaucoma is the second leading cause of blindness worldwide. Even though significant advances have been made in its management, currently available antiglaucoma therapies suffer from considerable drawbacks. Typically, the success and efficacy of glaucoma medications are undermined by their limited bioavailability to target tissues and the inadequate adherence demonstrated by patients with glaucoma. The latter is due to a gradual decrease in tolerability of lifelong topical therapies and the significant burden to patients of prescribed stepwise antiglaucoma regimens with frequent dosing which impact quality of life. On the other hand, glaucoma surgery is restricted by the inability of antifibrotic agents to efficiently control the wound healing process without causing severe collateral damage and long-term complications. Evolution of the treatment paradigm for patients with glaucoma will ideally include prevention of retinal ganglion cell degeneration by the successful delivery of neurotrophic factors, anti-inflammatory drugs, and gene therapies. Nanotechnology-based treatments may surpass the limitations of currently available glaucoma therapies through optimized targeted drug delivery, increased bioavailability, and controlled release. This review addresses the recent advances in glaucoma treatment strategies employing nanotechnology, including medical and surgical management, neuroregeneration, and neuroprotection.

Ocular Surface Disease and Glaucoma Medications: A Clinical Approach

OBJECTIVES

Ocular surface disease frequently coexists with glaucoma and may be initiated or exacerbated by topical glaucoma medications. We performed a review of current literature to assess the prevalence, causes, and treatment of ocular surface disease in glaucoma patients, specifically those on topical therapy.

METHODS

A Pubmed database search was conducted. A total of 720 articles published from 1972 to 2018 were found in relation with ocular surface disease, glaucoma, and glaucoma medications. Of these, 102 articles were included in this analysis. We included primary and empirical studies for patients on topical glaucoma medications. Exclusion criteria included case reports, non-English studies, and articles unrelated to the primary subject of this review.

RESULTS

Ocular surface disease among normal and glaucomatous eyes was evaluated based on diagnostic testing including clinical examination and questionnaires to determine visual function and quality of life. Glaucoma medications can be associated with toxicities to the ocular surface, most often due to the nature of the preservative included in the medication; however, the incidence of toxicity can be mitigated by the use of preservative free medications, decreased preservative medications, or treatment of dry eye disease. Treatment of glaucoma with laser trabeculoplasty or minimally invasive glaucoma surgeries that spare the conjunctiva and the cornea may avoid or decrease reliance on topical glaucoma medications, potentially avoiding the initiation or progression of ocular surface disease.

CONCLUSIONS

Recognition and treatment of ocular surface disease in glaucoma patients may improve patient quality of life and medication adherence. This may ultimately improve glaucoma treatment outcomes.

Development and characterisation of electrospun timolol maleate-loaded polymeric contact lens coatings containing various permeation enhancers

Despite exponential growth in research relating to sustained and controlled ocular drug delivery, anatomical and chemical barriers of the eye still pose formulation challenges. Nanotechnology integration into the pharmaceutical industry has aided efforts in potential ocular drug device development. Here, the integration and in vitro effect of four different permeation enhancers (PEs) on the release of anti-glaucoma drug timolol maleate (TM) from polymeric nanofiber formulations is explored. Electrohydrodynamic (EHD) engineering, more specifically electrospinning, was used to engineer nanofibers (NFs) which coated the exterior of contact lenses. Parameters used for engineering included flow rates ranging from 8 to 15μL/min and a novel EHD deposition system was used; capable of hosting four lenses, masked template and a ground electrode to direct charged atomised structures. SEM analysis of the electrospun structures confirmed the presence of smooth nano-fibers; whilst thermal analysis confirmed the stability of all formulations. In vitro release studies demonstrated a triphasic release; initial burst release with two subsequent sustained release phases with most of the drug being released after 24h (86.7%) Biological evaluation studies confirmed the tolerability of all formulations tested with release kinetics modelling results showing drug release was via quasi-Fickian or Fickian diffusion. There were evident differences (p<0.05) in TM release dependant on permeation enhancer.

In Vivo Measurement of Human Corneal Impedance Value

PURPOSE

To examine the validity of in vivo electrical corneal resistance (CR) measurements taken by a corneal resistance device (CRD).

METHODS

Eighty-two eyes (mean age ± SD, 50.1 ± 23.3; range, 22-87 years: 50 eyes of 33 males and 32 eyes of 17 females) of patients who had undergone cataract surgery and volunteers at the Kanazawa Medical University Hospital were enrolled. The CR was compared among gender; age; side, that is, left versus right eye; healthy (fluorescein-negative) versus epithelium-injured eyes (fluorescein-positive), corneal radius of curvature; corneal endothelial cell count; and corneal thickness.

RESULTS

The mean ± SD of the CR in the 82 eyes was 273.2 ± 78.2 Ω. By age group, the mean ± SD CR was 283.3 ± 87.4 Ω (30 eyes) in the 20s, 275.0 ± 50.0 Ω (4 eyes) in the 30s, 266.7 ± 70.7 Ω (9 eyes) in the 40s, 257.1 ± 53.5 Ω (7 eyes) in the 50s, 242.9 ± 78.7 Ω (7 eyes) in the 60s, 266.7 ± 84.0 Ω (18 eyes) in the 70s, and 300.0 ± 81.6 Ω (7 eyes) in the 80s, with no significant difference among the groups. By gender, the mean ± SD CR was 270.0 ± 83.0 Ω (50 eyes) in males and 278.0 ± 71.0 Ω (32 eyes) in females. By side, the CR values were 282.9 ± 83.4 Ω (44 eyes) in the right eye, 265.9 ± 71.3 Ω (41 eyes) in the left eye, with no significant difference among the groups. By status, the values were 280.0 ± 70.0 Ω (44 eyes) in healthy eyes and 200.0 ± 144.2 Ω (13 eyes) in injured eyes, with a significant between-group difference (P = 0.009). The mean ± SD corneal thickness (0.56 ± 0.03 mm) in 46 healthy eyes was slightly correlated with the CR.

CONCLUSIONS

The CRD quantitatively measured the CR in healthy eyes. The CR did not differ significantly by age, gender, or left versus right eye. The significant difference in CR between the healthy and injured eyes showed that the measurements have validity.

Fixed combination of travoprost and timolol maleate reduces intraocular pressure in Japanese patients with primary open-angle glaucoma or ocular hypertension: analysis by prostaglandin analogue

BACKGROUND

We have shown a decrease in mean intraocular pressure (IOP) by switching to travoprost/timolol fixed combination (TTFC) in subjects receiving prostaglandin analogue (PGA) monotherapy and requiring additional medication in a previous report. For analyzing factors affecting IOP reduction, baseline IOP and preceding PGA were selected as statistically and clinically significant factors. In this report, we examine IOP-lowering effect and adverse drug reactions by preceding PGA.

METHODS

Patients with primary open angle glaucoma or ocular hypertension who received monotherapy with one of four PGAs (travoprost, latanoprost, tafluprost, or bimatoprost) for at least 3 months at 26 institutions and were determined to require additional medication by their primary physician were included. IOP reduction and adverse events were examined at 4, 8, and 12 weeks for each of four PGAs after switching to TTFC.

RESULTS

In total, 157 patients who could be followed up for at least 4 weeks after switching to TTFC were included in the efficacy analysis. Multiple regression analysis was performed, and baseline IOP and PGA were found to be significant factors to IOP reduction. IOP reduction at week 12, adjusted with the regression model, was -3.5, -1.8, and -1.4 mmHg in the tafluprost, latanoprost, and travoprost groups, whereas it was -0.5 mmHg in the bimatoprost group. Along with differences in baseline IOP between groups, an IOP-lowering effect of >1 mmHg was noted in the tafluprost, latanoprost, and travoprost groups after the switch. IOP was maintained at 13.8-14.8 mmHg throughout the follow-up period. No serious adverse events or noteworthy issues were observed in any group after the switch.

CONCLUSION

Clinically significant IOP-reducing effects of TTFC were observed in the latanoprost, travoprost, and tafluprost groups when switching from each PGA monotherapy, while there were some differences in effects between groups, with minimal safety concerns.